Corrosion of Lead-Acid Battery Electrodes in Sulphuric Acid

ِ◌ ِ◌University 

of Baghdad 

College of Science 

Chemistry Department 

Corrosion of Lead-Acid 

Battery Electrodes 

in 

Sulphuric Acid 

A thesis 

Submitted to the College of Science of Baghdad 

University as a partial fulfillment of the requirements 

for the degree of Master of Science in Chemistry 

By 

Bakhtiar Kakil Hamad 

(B.Sc.) 

2000 

October 2004

Supervisors Certificate 

I certify that this thesis was prepared under my supervision 

at the College of Science, University of Baghdad in partial 

fulfillment of the requirements for the degree of Master of 

Science in Chemistry. 

Signature 

Prof. Dr. Jalal Mohammed Saleh 

Date: / /2004 

In view of the above recommendation, I forward this thesis 

for debate by Examining Committee. 

Signature: 

Name : 

Address : 

Date : / /2004

Committee Certificate 

We certify that we have read this thesis and as examining 

committee examined the student (Bakhtiar Kakil Hamad) in its 

content and that in our opinion it meets the standard of a thesis 

for the degree of Master of Science in Chemistry. 

Chairman Member 

Signature: Signature: 

Name: Name: 

Date: Date: 

Member Member( Supervisor) 

Signature: Signature: 

Name: Name: 

Date: Date: 

In view of the above recommendation, I forward this thesis 

for debate by Examining Committee. 

Signature: 

Name: 

Address: 

Date:

Acknowledgements 

I would like to express my sincere thanks and gratitude to my 

supervisor prof. Dr. Jalal Mhammed Saleh, Ph.D., C. Chem. D. Sc., 

FRSC. For his close supervision, encouragement and invariable 

guidance throughout this research. 

I wish to give my special thanks and appreciation to prof. Naema 

Ahmed Hikmat, for her encouragement and care. 

Special thanks are due to the staff of the State Company of 

Battery Manufacturing for supplying the starting materials. 

Finally, my sincere thanks are due to my family for their patience 

and support during the duration of my studies. Above all my great 

thanks to God for his mercy and blesses. 

Bakhtiar

Summary 

The present work involved the investigation of the polarization 

behaviours of the following materials which consisted the electrodes and 

components of the lead acid battery which were: 

1, lead alloy working electrode, 

2, Grid lead electrode, 

3, Pure lead electrode, 

4, uncured positive electrode, 

5, cured positive electrode, 

6, uncured negative electrode, and, 

7, cured negative electrode. 

In 0.1, 0.25 and 0.56 M sulphuric acid solution in the temperature 

range (298-318)K in four different corrosion media which were: 

1, un-stirred oxygenated sulphuric acid, 

2, stirred oxygenated acid solution, 

3, un-stirred deaerated acid solution, and, 

4, stirred deaerated acid solution. 

The major aspects of the work and the main results obtained may be 

presented as follows: 

1- The polarization behaviour studies were performed on the different 

lead electrodes in the different media has been examined using a 

potentiostat and a scan rate of (30)mm per minute. The potentioscan 

covered a range from –2.0 to +2.0 Volt. The main results obtained 

were expressed in terms of the corrosion potentials (Ec) which became 

more negative in the un-stirred deaerated acid solution as compared 

with the oxygenated acid solution, and also in terms of corrosion current 

densities (ic) which became higher in the stirred oxygenated acid

solution. Thus, corrosion was more intense in the oxygenated acid 

solution as compared with the deaerated acid solution. 

2- The corrosion potentials and the corrosion current densities changed 

considerably in the presence of the additives which involved :- 

1, H3PO4 ( 11g dm -3 ), 

2, A mixture of ( H3PO4(11g dm -3 )+ FeSO4(0.2 g dm -3 )), 

3, NaCl (4 g dm -3 ) and , 

4, FeSO4 (0.2 g dm -3 ). 

In the stirred and the un-stirred oxygenated 0.56M sulphuric acid solution 

in the temperature range (298-318)K using the following working 

electrodes: 

1, lead alloy electrode, 

2, grid lead electrode, 

3, cured positive electrode, and , 

4, cured negative electrode. 

Values of the corrosion potential (Ec) became more negative in the 

presence of H3PO4 and less negative with NaCl additives, the values of the 

corrosion current densities for all the electrodes were higher with NaCl 

and lower with H3PO4 in the both media. 

3- The protection efficiency (p%) was investigated for the additives in 

the stirred and the un-stirred oxygenated 0.56M sulphuric acid 

solution. Maximum values of p% were attained with H3PO4 and the 

minimum with NaCl. 

4- Values of the thermodynamic quantities (DG, DW and DH) were 

estimated for the corrosion of the electrodes. DG values were more 

negative in the deaerated acid solution in the absence of additives. In the 

presence of the H3PO4, DG values were more negative while in the 

presence of NaCl the values were less negative indicating a greater 

corrosion feasibility in the former and smaller in the latter cases. DW

values extended over a wider range. Such variation of DW values 

generally depended on the type and extent of the variation of DG vales 

with temperature. As a result of such variations, values of DH were also 

found to a quire appreciably negative values. 

5- The kinetics of the corrosion followed Arrhenius type rate equation. 

A linear relationship existed between the values of the activation energy 

(Ea) and logarithm of the pre-exponential factor (log A) in the four 

different media suggesting the operation of a compensation effect in the 

kinetics of corrosion. This suggests that, the corrosion reaction proceed 

on surface sites, which were associated with different energies of 

activation (Ea). The corrosion reaction is assumed to start on sites with 

lower Ea and log A values first, spreading thereafter to these sites on 

which Ea and log A were higher.

CONTENTS 

Subject 

CHAPTER ONE: INTRODUCTION 

a 

Page 

No. 

1.1- Lead-Acid Storage Battery 1 

1.1.1- The industrial production of Leady oxide 2 

1.1.1.1- Barton-pot process 

1.1.1.2- Ball-Mill Process 

3 

1.1.2- Industrial preparation of the Electrodes 4 

1.1.3- Structure of the Electrode Materials 6 

1.1.3.1- PAM Structure 

1.1.3.2- NAM Structure 9 

1.1.4-The Electrolyte 12 

1.1.5- The cell structure and Reactions 13 

1.1.6- The Positive Electrode 14 

1.1.7- The Negative Electrode 15 

1.1.8- Curing of the Battery Electrodes 16 

1.1.9- Charging and Discharging Processes 17 

1.2- Corrosion of Battery Electrodes 20 

1.3- Corrosion of Lead and Lead Alloys 21 

1.4- The Literature Survey 22 

1.5- The Object and Scope of the Present Research 25 

CHAPTER TWO: EXPERIMENTAL 

2.1- The Experimental Set-Up 28 

2.2- The Working Electrode 29 

2.3- The Auxiliary Electrode 30 

2.4- The Reference Electrode 31 

2.5- The Corrosion Cell 32 

2 

6

Subject 

b 

Page 

No. 

2.6- Potentiostatic Measurement 34 

2.7- The Experimental Techniques and Procedure 36 

2.8- The Chemicals 38 

CHAPTER THREE: RESULT AND DISCUSSION 

POLARIZATION IN SULPHURIC ACID IN THE 

ABSENCE OF ADDITIVES 

3.1-The Polarization Curves. 39 

3.2- Results of the Polarization Curves. 45 

3.2.1- Corrosion Potentials (Ec). 61 

3.2.2- Corrosion Current Densities (ic). 69 

3.2.3- Passive Potentials (Ep). 76 

3.2.4- Passive Current Densities (ip). 77 

3.3- Tafel slopes and Transfer Coefficients. 78 

3.4- Polarization Resistance. 80 

3.5-Thermodynamics of Corrosion. 82 

3.6- Kinetics of Corrosion. 88 

CHAPTER FOUR: RESULT AND DISCUSSION 

POLARIZATION IN SULPHURIC ACID IN THE 

PRESENCE OF ADDITIVES 

4.1- Results of the Polarization Curves. 96 

4.1.1- Corrosion Potentials (Ec). 101 

4.1.2- Corrosion Current Densities (ic). 107 

4.1.3- Passive Potentials (Ep). 

4.1.4- Passive Current Densities (ip). 

112 

114 

4.2- Tafel slopes and Transfer Coefficients. 116 

4.3- Polarization Resistance. 118

Subject 

c 

Page 

No. 

4.4- Effect of Additives. 120 

4.4.1- Phosphoric Acid 120 

4.4.2- Mixture of H3PO4 and FeSO4 121 

4.4.3- Ferrous Sulphate (FeSO4) 122 

4.4.4- Sodium Chloride 122 

4.5- Protection Efficiency 123 

4.6- Thermodynamics of Corrosion. 134 

4.7- Kinetics of Corrosion. 149 

CHAPTER FIVE: CONCLUSIONS AND 

SUGGESTIONS FOR FUTURE RESEARCH 

5.1- Conclusions 166 

5.2- Suggestions for future research 167 

REFERENCES 168

Symbols and Abbreviations 

Symbol Definition Units 

A Pre-exponential factor Molecules. Cm -2 .s -1 

ba Anodic Tafel slope V decade –1 

bc Cathodic Tafel slope V decade –1 

C Molar concentration Mole. dm -3 

Ea Activation energy k J mol -1 

Ec Corrosion potential V (S.C.E) 

Ecr Critical potential V (S.C.E) 

Ep Passive potential V (S.C.E) 

F Faraday constant C mol -1 

DG Gibbs free energy change k J mol -1 

DH Enthalpy change k J mol -1 

i Current density A cm -2 

ic Corrosion current density A cm -2 

icr Critical current density A cm -2 

ip Passive current A cm -2 

n Number of electrons 

NAM Negative active mass 

P Protection efficiency 

PAM Positive active mass 

R Gas constant J. mol -1 .K -1 

SCE Saturated calomel electrode V 

DS Entropy change J. mol -1 .K -1 

DS „ Entropy of activation J. mol -1 .K -1 

T The temperature in Kelvin K 

a Transfer Coefficient 

aa Anodic Transfer Coefficient 

ac Cathodic Transfer Coefficient

1.1-Lead –Acid Storage Battery 

The lead acid battery was the first, commercially successful, 

rechargeable battery. It was invented in 1859 by G. Plante and has 

undergone steady improvement ever since (1) . 

A typical (12)V lead-acid car battery has six cells connected in series, 

each of which delivers about 2V. Each cell contains two lead grids packed 

with the electrode materials. The anode is spongy Pb, and the cathode is 

powdered PbO2. The grids are immersed in an electrolyte solution of ~ 4.5 

M H2SO4 fiberglass sheets between the grids prevent shorting by accidental 

physical contact. When the cell discharges, it generates electrical energy as 

a voltaic cell with reactions: 

Anode (oxidation): 

Cathode(reduction): 

Pb(s) + SO4 2- (aq) fi PbSO4(s) + 2e - (1-1) 

PbO2(s) + 4H + (aq) + SO4 2- (aq)+ 2e fi PbSO4(s) + 2H2O(l) (1-2) 

Note that both half-reactions produce Pb 2+ ions, one through oxidation 

of Pb, the other through reduction of PbO2. At both electrodes , the Pb 2+ 

ions react with SO4 2- to form insoluble PbSO4(s) (2) . 

The overall electrochemical process can be represented by the 

equation (3) : 

discharge 

Pb(s) + PbO2(s) + 2H2SO4(aq) 2PbSO4(s)+ 2H2O(l) (1-3) 

charge 

The grids make an important part of the storage cell which act as 

supports for the active materials of plates and conduct the electric current 

developed. It also plays an important role in maintaining uniform current 

distribution throughout the mass of the active material. Grids for both 

(1)

positive and negative plates are frequently of the same design, composition, 

and weight. 

The lead storage battery is the most widely applied storage battery in 

the world today (4) . 

1.1.1-The industrial production of Leady oxide 

The basic starting material for lead –acid battery plates is generally 

referred to as “leady” or “ grey” oxide. This material is prepared by 

reacting a lead feedstock with oxygen in either a Barton pot or a Ball Mill, 

and usually comprises about one-part unreacted fine lead particles 

(so-called ‘free lead’) and three parts lead monoxide (a-PbO and b-PbO). 

A small amount of red lead (Pb3O4) can also be produced, but battery 

manufactures generally prefer to add this oxide from a separate source. The 

blending (or indeed complete substitution) of leady oxide with red lead is 

particularly popular in the preparation of tubular positive plates (5) . The 

Barton-pot and Ball-Mill processes remained the principle methods for 

producing leady oxide for lead–acid battery paste. 

1.1.1.1-Barton-pot Process 

In the Barton-pot approach to making battery oxide, lead is melted, 

forced into a spray of droplets, and then oxidized by air at a regulated 

temperature. Any accumulated bulk molten lead is broken up again into 

droplets by a revolving paddle that directs the lead against a fixed baffle 

arrangement inside the pot. By careful control of the : 

¤ pot temperature, 

¤ paddle rotation speed and, 

¤ rate of air flow. 

(2)

Battery oxide of the desired chemical composition and particle – size 

distribution can be obtained (5) . The oxide so produced is a mixture of 

tetragonal ( a-PbO) and orthorhombic (b-Pbo) lead monoxide together with 

some unreacted lead. The oxide usually consists of (65-80 w%) PbO (6,7) . 

The problem with the Borton-pot system is that of controlling the pot 

temperature. If the temperature is excessive above 488 o C a large amount of 

b-PbO can be formed; which is considered undesirable in the final product 

because of its effects on performance and life of the finished plate if the 

amount of b-PbO exceeds 15% (8,9) . 

1.1.1.2-Ball-Mill Process 

The alternative means for preparing battery oxide the Ball–Mill 

process- involves tumbling lead balls, cylinders, billets or entire ingots in a 

rotating steel drum through which a stream of air is passed. The heat 

generated by friction between the lead pieces is sufficient to start oxide 

formation. The reaction generates more heat and thus allows the lead 

particles that are rubbed off by the abrasion to be converted to leady oxide 

of the required composition. 

The relative amounts of the oxide constituents can be controlled by 

manipulation of the operational parameters governing the oxide-making 

process, namely (5) : 

¤ mill temperature, 

¤ mill speed, 

¤ flow rate and temperature of the air steam, and , 

¤ amount of mill charge. 

The oxide usually consists of (60-65wt %) of a-PbO, with remainder being 

free lead (8) . 

(3)

1.1.2-Industrial preparation of the Electrodes 

The pastes now commonly used in making the familiar pasted –plate 

batteries are prepared by mixing some particular lead oxide or blend of 

oxides with aqueous sulphuric acid (sp. gr. 1.4) and water. Free lead and 

different basic lead sulphates have been found in the paste as the 

monobasic lead sulphate, the dibasic lead sulphate, the tribasic lead 

sulphate, and finally tetrabasic lead sulphate. In first, normal lead sulphate 

is produced according to the following equation: (10) 

PbO + H2SO4 fi PbSO4 + H2O (1-4) 

and then the normal lead sulphate produced reacts with additional lead 

oxide to form basic compounds. Both water and sulphuric acid serve 

necessary functions in the pasting of battery oxide mixes.The water acts as 

lubricant producing a lighter paste. As the plate dries the evaporation of 

this water gives a desirable porosity. The sulphuric acid forms lead 

sulphate which, in addition to expanding the paste and giving it great 

porosity, supplies a necessary binding cement so that the dry plate can be 

handled without loss of material. 

The prepared paste is applied to the grid by machine pasting 

equipment. Freshly pasted plates are passed through a drying oven to 

harden their surface somewhat. They are left in the oven for 72hr to enable 

the so-called curing process to take place. During the curing operation the 

relative humidity in the curing ovens must be 100%, such humidity takes 

part in oxidation reaction. The temperature is responsible for the 

composition of cured plates, such plates cured at high temperature (more 

than 70 o C) resulting in mainly tetrabasic lead sulphate 4PbO. PbSO4 (4BS) 

behave markedly different to those cured at low temperature having only 

tribasic lead sulphate 3PbO. PbSO4. H2O (3BS) (11,12) . The surfaces are of 

active material and depend on curing temperature, as the suitable 

temperature in curing process is around (56-65 o C) (13) . 

(4)

The final process for preparation of lead–acid battery plates is the 

formation. Formation of the plates is necessary to convert the inactive lead 

oxide-sulphate paste into the active electrode materials of the finished cell 

Essentially it is an oxidation reduction reaction wherein the positive plates 

are oxidized from lead oxide to lead dioxide, and the negative plates are 

reduced from lead oxide to sponge lead. 

The negative plates are similarly made except that so-called 

“expanders” are added. Expanders are necessary in negative plates to 

activate the plates at low temperatures and high rates of discharge. 

Three materials constitute what are commonly called negative expanders. 

They are carbon black, barium sulphate, and organic materials such as 

lignin (14,15) . The presence of the lignin, however, renders the lead sulphate 

film porous (16) . 

A number of theories have been proposed to account for the reaction 

taking place in the lead-acid battery. The double- sulphate theory is now 

generally accepted. Gladstone and Tribe first proposed this theory in 

1882 (17) . The double–sulphate theory is most conveniently stated by the 

equation(1-3) (18) ,which indicate that the overal reaction leads to the 

formation of the lead sulphate on the lead acid battery electrodes that is, 

both positive and negative plates will be converted to the lead sulphate at 

the end. 

(5)

1.1.3-Structure of the Electrode Materials 

1.1.3.1-PAM Structure 

The structure of PAM (positive active mass) obtained during 

formation of the plates consists of two structural levels and is presented as 

in Fig.(1-1) and described in the following sections: 

Fig.(1-1) 

a- Microstructural. The smallest building element of PAM structure is the 

PbO2 particle. A certain number of PbO2 particles interconnect into 

agglomerates. At this microstructural level the electrochemical reaction 

of discharge proceeds. This level determines the active surface area of 

PAM. 

b- Macrostructural level. A huge number of agglomerates, and in some 

cases individual particles, interconnect to form aggregates (branches) or 

porous mass. Micropores are formed between the agglomerates building 

up the aggregates. Aggregates interconnect to form (i) Skeleton, which 

is connected to the grid through an interface or (ii) porous mass. 

Macropores are formed between the aggregates along which H2SO4 and 

H2O flows move between the plate interior and the bulk of the 

electrolyte (19,20) . 

(a) (b) 

(6)

Fig.(1-2) presents structure of the three types of PbO2 particles: 

spherical or egg-shaped, PbO2 crystal particles and needle-like particles. 

Fig.(1-2) 

A heterogenous mass distribution is observed in the bulk of PbO2 Particles 

Fig.(1-3). 

Fig.(1-3). 

Dark zones have crystal structure (a or b PbO2) and sizes 20 to 40 nm. 

More electron transparent zone are hydrated (gel zones). Hence PbO2 

particles have crystal/gel structure. About 31-34% of PAM is 

hydrated (21,22) . 

(7)

The mechanism of the formation of PbO2 particles involves 

Pb 4+ + 4H2O fi Pb(OH)4 + 4H + (1-5) 

Pb(OH)4 dehydrates partially as a result gel particles to form: 

nPb(OH)4fi [ PbO(OH)2]n + n H2O (1-6) 

[PbO(OH)2]n stands for a gel particle. Further dehydration takes place and 

PbO2 crystal zones are formed. 

[PbO(OH)2]n‹fi [kPbO2+(n-k)PbO(OH)2]n + k H2O (1-7) 

Crystalzone gel zone 

Hydrated zones exchange ions with the solution (PbO2 particle is an 

open system). The ratio between crystal and gel zones influences the 

capacity of the plate. 

(8)

1.1.3.2-NAM STRUCTURE 

NAM (negative active mass) structure consists of lead crystals 

interlinked in a skeleton network Fig.(1-4) and secondary structure of 

separated lead crystals which are precipitated on the lead skeleton surface 

Fig.(1-5) (23,24) . 

Fig.(1-4) Fig.(1-5) 

The skeleton structure is formed during the first stage of formation 

when PbO and basic lead sulphates partially reduced to lead and partially 

react with H2SO4 to give PbSO4. 

These processes proceed at a neutral pH solution in the pores of cured 

plates. The secondary structure is formed during the second stage of the 

formation when PbSO4 crystals are reduced to lead crystals under acidic 

conditions. Upon discharge, current is generated mainly at expense of the 

oxidation of the secondary lead structure (energetic structure). The primary 

(skeleton) structure serves both as a current collector and a mechanical 

support of the energetic structure. The energetic structure participates 

mainly in the charge discharge processes of the negative plates (25,26) . 

Pb 2+ ions are formed at the lead/ anodic layer interface. Under the 

action of the electric field they reach the second interface and return to the 

solution. Since the solution is saturated with respect to PbSO4 the Pb 2+ ions 

(9)

diffuse to the growth front of some of the lead sulphate crystals and are 

incorporated in it. Owing to these processes of transport of Pb 2+ through the 

anodic layer, microvoids are formed between the lead sulphate crystals and 

the lead surface, Fig.(1-6) (27) . 

(10)

Potential vs Hg/Hg2SO4 

Microns 

Fig.(1-6) 

Representation of the multi-phase corrosion layer by Ruetschi 

(11) 

Microns

1.1.4-The Electrolyte 

Sulphuric acid of battery is a heavy transparent oily liquid having no 

odour and easily soluble in water. When the acid is dissolved in water it 

heats the solution very highly. This acid attacks leather, paper, cloth. It is 

used for making the electrolyte for Lead-Acid batteries (28) . The specific 

gravity of sulphuric acid depends on the temperature and decreases with 

increasing temperature. 

During formation, the acid used to make the paste is released and 

some water is lost due to gas evolution so that the concentration at the end 

will be higher than at the beginning. 

After charging, the batteries require leveling of the electrolyte. This is 

primarily due to the fact that the batteries are normally not filled to the 

correct level in the first time to allow for gassing and secondly to make up 

for the water losses during charging. The leveling should be possible with 

standard operation acid, i.e. specific gravity 1.28 g/ml. As shown in table 

(1-1) (29) . 

Table(1-1): Specific gravity of sulphuric acid and charge conditions in 

lead-acid storage battery. 

Electrolyte specific gravity The charge energy 

1.28-1.25 Full charge 

1.25-1.20 Suitable 

1.20-1.16 Vacancy 

1.16-1.08 Full vacancy 

Less than 1.08 Un- rechargable 

(12)

1.1.5- The cell structure and Reactions 

The Pb-H2SO4 cell system for the fully–charged cell can be 

represented it as in the following: (A) (7) : 

Pb H2SO4 PbO2 

Anode(-) solution Cathod(+) 

When the cell is connected to the external circuit (the process called cell 

discharging )the left electrode (Anode) oxidized as : 

L: Pb = Pb 2+ + 2e (1-8) 

Two electrons are generated and transferred within the external circuit 

to the right electrode (cathode) and the reduction occur as: 

R: PbO2 + 4H3O + + 2e = Pb 2+ + 6H2O (1-9) 

The collection of (1-8) with (1-9) reactions may be made as: 

Pb + PbO2 + 4H3O + = 2Pb 2+ + 6H2O (1-10) 

adding (2SO4 2- ) to the reaction (1-10) we obtains: 

Pb + PbO2 + 2H2SO4 = 2PbSO4(s)+ 2H2O (1-11) 

The symbol (s) for PbSO4(s) means an insoluble salt in electrolyte solution 

which covers the plates surfaces. The reaction (1-11) is a discharge process 

and converts the electrodes to lead sulphate. The measuring of the specific 

gravity of the acid electrolyte solution during discharging process helps to 

estimate the remaining life of the battery. 

The chemical structure of the fully – discharged cell may be represented as 

in B: 

B 

PbSO4(s) H2O PbSO4 

Anode(-) Cathode(+) 

(13)

Considering the remaining (un-reacted) lead and lead dioxide of the 

electrodes are can re-write the cell (B) as cell(C): 

C 

Pb,PbSO4(s) ‰ H2O ‰PbSO4(s), PbO2 

The left electrode is therefore made of lead and lead sulphate and the 

right electrode is compared of lead dioxide and lead sulphate. 

When the discharged cell is exposed to a charging process the 

reactions which occur at the electrodes are: 

L: PbSO4(s) + 2e = Pb + SO4 2- 

(14) 

(1-12) 

This is reduction process and the oxidation occurs at the right 

electrode as: 

R: PbSO4(s) +2H2O= PbO2+ SO4 2- + 4H + + 2e (1-13) 

The overall reaction may be represented as summation of (1-12) and 

(1-13) reactions as: 

2PbSO4(s) +2H2O= Pb + PbO2+ SO4 2- + 4H + ….. (1-14) 

Or: 

2PbSO4(s) +2H2O= Pb + PbO2+ 2H2SO4 2- …. (1-15) 

This explain that the battery charging by an external current converts 

the left electrode to lead and the right to lead dioxide and the water is 

converted to sulphuric acid. Thus, the battery restores its original state by 

such operation (30) . 

1.1.6- The Positive Electrode 

The electrochemical reactions at the positive electrode are usually 

expressed as: 

PbO2(s) +4H + (aq)+SO4(aq) 2- discharge 

+2e… PbSO4(s) + 2 H2O(l) (1-16) 

charge 

An important feature of the positive electrode discharge concerns the 

nature of the PbSO4 deposit since the formation of dense, coherent layers

can lead to rapid electrode passivation. Lead dioxide exists in two 

crystalline forms, rhombic (a-) and tetragonal (b-), both of which are 

present in freshly formed electrode structures. 

Positive electrodes are manufactured in three forms, as plante plates, 

pasted plates and tubular plates. In plante plates, the positive active 

material is formed by electrochemical oxidation of the surface of a cast 

sheet of pure lead to form a thin Layer of PbO2. The plate generally has a 

grooved structure to increase its surface. Such plates have a very long life. 

Since they have a large excess of lead which can subsequently be oxidized 

to PbO2 (31) . Tubular plates consist of a row of tubes containing axial lead 

rods surrounded by active material. The tubes are formed of fabrics such 

as terylene or glass fibre or of perforated synthetic insulators which are 

permeable to the electrolyte. Lead dioxide electrode system (Pb/ PbO2/ 

PbSO4) formed at potentials above +0.950 V (32,33) . 

1.1.7- The Negative Electrode: 

The reactions of the negative electrode are generally given as: 

PbO(s) +SO 2- discharge 

4(aq) PbSO4(s) + 2e (1-17) 

charge 

Negative electrodes are almost exclusively formed of pasted plates , using 

either fine mesh grids or coarse grids covered with perforated lead foil (box 

plates) and the same paste used in positive plate manufacture. When the 

paste is reduced under carefully controlled condition, highly porous sponge 

lead is formed consisting of a mass of a cicular (needle-like) crystals which 

give a high electrode area and good electrolyte circulation (31) . Additives 

such as very fine BaSO4, which is isomorphic with PbSO4, encourages the 

formation of a porous non-passivating layer of lead sulphate. The precise 

mechanism of the additive effects is complex and not completely 

(15)

understood. It is known that BaSO4 and the organic additives interact, since 

together they are much more effective than the sum of their individual 

contributions. 

Lead/Lead sulphate electrode system (Pb/PbSO4) is formed within the 

potential region from –0.950 to –0.400 V vs. a calomel reference 

electrode (34) . 

1.1.8-Curing of the Battery Electrodes 

The curing process consists of the conversion of wet pasted plates to 

a dry, crack free, unformed plate of sufficient strength and adhesion to the 

grid. During this process two steps proceed simultaneously and in 

sequence:- 

1. water loss by shrinkage. 

2. Void formation. 

Curing is an important part of manufacturing, for if it is not properly 

carried out capacity and especially life expectancy are adversely 

influenced. The curing can be done in different ways. 

1. The plates are suspended individually on racks with small separation 

according to a pre-established program, the plates are subjected to a 

flow of damp or dry air and finally heated. The curing and drying lasts 

about 16 to 24 hours. 

2. The plates are hang on chains and moved through a tunnel kiln in 

which temperature is increased and humidity is decreased. The kiln is 

usually heated with CO2-containing combustion gas which passes 

through the kiln. 

3. The plates are flash-dried by gas heating or infrared heating so that they 

may be packed densely 20 to 30 cm high without sticking. They are 

covered to prevent the process from proceeding too rapidly, otherwise 

(16)

small cracks will appear. For oxidation and drying in stacks 4 to 6 days 

are required. 

4. The plates are dipped in sulphuric acid or sprayed with sulphuric acid 

to form a dense lead sulphate film on the surface, a process frequently 

used for tubular plates but less often for grid plates. 

After curing the paste in the plates must have sufficient dry strength 

and adequate adhesion to the grid so that it does not detach during sub 

sequent manufacturing steps and retains electrical contact with the grid 

during formation. 

Curing of positive plates take place when Pb oxidation of the 

paste/grid contact and drying of the paste. 

For operation duration of curing of negative plates has to be less than 

8 hours too. Additive to the negative plate increases the rate of curing 

process at 60C o and reduces the curing process to 8 hours. The expander 

destroys at temperature higher than 65C o(35,3) . 

1.1.9- Charging and Discharging Processes 

Formation of positive plates. It was found that formation of positive 

active mass (PAM) takes place in two stages (36) . 

a. During the first stage, H2SO4 and H2O penetrate from the bulk of 

the solution into the plate, As a result of chemical and 

electrochemical reactions PbO and basic sulphates are converted to 

a-PbO and b-PbO. 

b. During the second period of formation PbSO4 is oxidized to b- 

PbO2. H2SO4 originates and diffuses into the volume of electrolyte. 

Taking into account specific conditions of chemical and 

electrochemical reactions in porous electrodes a mechanism is suggested 

for formation processes of the PAM (37,38) . 

(17)

Formation of the negative active mass: It was established that it takes 

place also in two stages: 

a. During the first stage electrochemical reduction of PbO and basic lead 

sulphates occur and lead skeleton is formed. Beside, in these processes 

chemical reactions of PbSO4 formation also proceed. PbSO4 crystal 

remain included in lead skeleton. The (PbSO4 + Pb) zones are formed in 

the both surfaces of the paste and advance into the interior of the plate. 

b. During the second stage, reduction of PbSO4 to Pb occurs and the 

obtained lead crystals are deposited on the lead skeleton surface in 

strongly acidic solution. The mechanism of the elementary chemical and 

electrochemical reactions as well as their mutual relationships are 

determined. During formation, both the pore radii and the porosity of 

the active mass increase (39,40) . Fig.(1-7) Shows the Discharge and change 

processes of the lead acid battery. 

(18)

Fig.(1-7): Discharge and charge processes of the battery 

(19)

1.2- Corrosion of Battery Electrodes 

The grids of the electrodes which serve as carriers for the active 

masses conductors for the electric current are manufactured from lead and 

alloys by casting. Other methods such as punching or stretching are 

common. The process of disintegration of a metal grid structure starting the 

surface is called corrosion. 

Each nonnoble metal suffers corrosion in aqueous solution in which 

metal is dissolved anodically under hydrogen evolution or precipitated an 

insoluble compound, depending on the constituents of the solution. This 

reaction is small because of the high overvoltage of the hydrogen on lead 

with negative electrodes the portion of the surface of the grid compared 

with the total inner surface of the mass is small. Therefore a corrosion of 

the grid is not noticeable. The lead sulphate forms a dense cover layer to 

protect the grid. Failure of batteries due to corrosion of the negative grids is 

rarely observed. The hydrogen corrosion occurs often in cavities in the 

presence of organic substances and at higher operating temperatures. 

On positive grids corrosion leads to solid oxidation products, to 

reduction of the cross section of the grid rods, and thereby to a loss of 

conductivity and grid breakage. Often a deformation or increased growth of 

the grids is a related condition. 

The local cell corrosion on positive plates plays a only minor role. The 

corrosion under current, the anodic corrosion, however, is highly important. 

With current flow the process becomes dependent on potential. A 

schematic representation of the reaction products as a function of potential 

is shown in Fig.( ). Included here is the dependence on the hydrogen and 

sulphate ion concentration. 

(20)

A sign of grid corrosion is a reduced number of ampere hours 

obtained from the battery on discharge at the 10 hour rate. The positive 

electrode always limits the capacity. 

Cells containing plates destroyed by corrosion are no longer fit for 

service. Usually, corrosion of the grids is a sign of long service of the given 

cells. 

1.3- Corrosion of Lead and Lead Alloys 

Lead is used extensively in sulphuric acid in the lower concentration 

ranges. Corrosion is practically nil in the lower concentrations but increases 

as temperature and concentration increase. Rapid attack occurs in 

concentrated acid because the lead sulphate surface film is soluble (46,47) . 

This is the lead used for corrosion applications. High purity lead is less 

resistant particularly in the stronger and hotter acids and also exhibits 

poorer mechanical properties. 

Lead depends on the formation of a lead sulphate-lead protective 

surface long life in sulphuric acid environments, and in many cases more 

than 20 years service is obtained. Lead gains weight when exposed to 

sulphuric acid because of the surface coating or corrosion product formed 

except in strong acid wherein the lead sulphate is soluble and not 

protective. 

Lead forms protective films consisting of corrosion products such as 

sulphates, oxides, and phosphates. 

A more realistic model of the corrosion product layer formed on lead 

has been proposed by Ruestchi as shown in Fig. (1-8) (48,49) . 

When corrosion resistance is required for process equipment, 

chemical lead containing about 0.06% copper is specified, particularly for 

sulphuric acid. This lead is resistant to sulphuric, chromic, hydrofluoric, 

(21)

and phosphoric acid. It is rapidly attacked by acetic acid and generally not 

used in nitric, hydrochloric, and organic acids (46) . 

1.4- The Literature Survey 

Fig. (1-8) 

Model of anodic layer 

(a) In the lead sulphate reagion. 

(b) In the lead monoxide region 

(c) In the lead dioxide region 

A study of the effect of corrosion of lead and lead alloys on the 

performance of the batteries due to sulphuric acid concentration, is of 

fundamental importance for increasing the useful life of these batteries (50) . 

Tedeschi (51) found that the rate of dissolution of lead prepared either 

by the reduction of PbO2 or PbO increases with the concentration of 

sulphuric acid solution. 

(22)

Pourbaix (52) expected on the basis of potential –PH diagrams, that in 

storage batteries of more than 6N. H2SO4 the solubility of the positive 

electrode is greater than the negative electrode owing to the formation of 

Pb 4+ ions. 

Lander (53) subjected lead to anodic corrosion at potentials near the 

reversible PbO2/PbSO4. Results indicate that the first step in the corrosion 

process was reaction of lead with water to form lead dioxide. Its potentials 

just below the reversible PbO2/PbSO4 potential, the corrosion of lead 

dioxide film to lead sulphate takes place. 

Casey (54) described three modes of reaction of lead in sulphuric acid 

depending on the acid strength, temperature, and the composition of the 

lead. Firstly a slight attack with vigorous evolution of hydrogen and finally 

complete decomposition with the evolution of sulphur dioxide. 

Corrosion rate of refined lead in 50 to 80% sulphuric acid was 

reported by Hohlstein and Pelzell who established the conditions of 

passivation (55) . 

Local action increases rapidly when the concentration of the acid is 

increased particularly for the negative plate. The temperatures to which the 

battery is subjected in service have an important bearing on the specific 

gravity of sulphuric acid. Battery exposed to low temperatures, such as 

automobile batteries in cold climates, require a high density of acid to 

permit their capacity to be utilized without depleting their electrolyte to so 

low specific gravity that freezing occurs. On the other hand, batteries for 

use in hot climates require a lower specific gravity because of the increased 

chemical activity at the higher temperature (56) . 

Abdul Azim (57) in the course of studying the behaviour of Pb-Ca 

alloys reported that the passive current for pure concentration increase as 

in sulphuric acid concentration increases from 0.1 to 10 N. 

(23)

Lead resists dilute sulphuric acid, even in presence of oxygen, owing 

to the low solubility of lead sulphate (58) . 

Many materials, which exhibit passively effects, are only negligibly 

affected by wide change in corrosive concentration. Other materials show 

similar behaviour expect at very high corrosive concentration when 

corrosion rate increases rapidly, lead shows this effect due to the fact that 

lead sulphate, which forms a protection in low concentration of sulphuric 

acid, is soluble in concentrated sulphuric acid (46) . 

Boctor (50) found that increasing temperature or sulphuric acid 

concentration increases the rate of self-discharge. 

Self discharge of positive plates is due to reaction between PbO2 in 

the active material and Pb in the grid (59) . 

Self discharge of negative plates is due to the reaction between 

sulphuric acid and the spong-lead, producing hydrogen gas and PbSO4 (50) . 

Antimony was introduced into the electrode system either by alloying 

it with the metal or by adding it to the H2SO4 solution. It was established 

that Sb lowers the oxygen over voltage and increases the rate of anodic 

corrosion of lead irrespective of the way in which it was introduced into the 

system (60) . 

Study of electrodes of different active mass layer thickness shows that 

with increase in thickness the corrosion rate decreases the corrosion rate 

decreases (61) . 

Chloride in the electrolyte of lead-acid batteries has long been thought 

to cause early failure due to accelerated corrosion of the positive-plate 

group. This study investigates the effect of chloride species, added as either 

hydrochloric acid or sodium chloride (62) . 

In the presence of H3PO4, the formation of soluble phosphate species 

causes the decrease of corrosion layer thickness. Higher than 0.9% 

concentration of H3PO4 negatively affect the behaviour of the electrodes, 

(24)

higher potentials being required for the oxidation of PbSO4 to PbO2, when 

the rate of oxygen evolution is also higher. Addition of FeSO4 with H3PO4 

to the electrolyte as a Fe 2+ ions prevents formation of Pb(IV) soluble ion 

which is undesirable (63,64) . 

Takao (65) examined the effects of temperature, the concentration of 

sulphuric acid, and the configuration of test specimens on negative 

electrode corrosion. The reason for this corrosion seems corroded areas are 

covered with electrolyte film that has a high resistance, so, they cannot be 

polarized to the full cathodic protection potential. 

Boctor (66) used an electrometric method for evaluation of the 

corrosion of lead alloys, the lead electrode is subjected to electrolyte and 

temperature condition , as well as to various states of polarization that 

simulate the service of lead-acid batteries. The resulting corrosion layer is 

first reduced to lead sulphate, then to sponge lead. A linear relation is 

observed between the weight of the corroded lead and the surface area of 

the sponge lead after cathodic reduction of the corrosion layer. 

Dragan (67) studied the effect of Sn and Ca doping on the corrosion of 

Pb anodes in lead-acid batteries and show that a small amount of Sn and Ca 

which was deposited on Pb by electrodeposition minimizes the weight of 

the anode corrosion. 

1.5-The Object and Scope of the Present Research 

The subject of this research included a number of important aspects 

which may be summarized as: 

1. Potentiostatic investigation of the corrosion behaviour of seven types 

of specimens of lead-acid battery plates at three concentrations (0.1, 

0.25 and 0.56 mol.dm -3 ) of stirred and un-stirred oxygenated sulphuric 

acid solution, and also with stirred and un-stirred deaerated sulphuric 

acid solution, at three temperatures 298, 308 and 318 K. 

(25)

2. The additive effect of phosphoric acid(11g), mixture of (Phosphoric 

acid(11g) + Ferrous Sulphate(0.2g)), Ferrous Sulphate (0.2g) and 

sodium chloride(4g) in 1 litre of sulhuric acid has been tested for the 

corrosion of four type of the following specimens. 

1. Lead alloy electrode. 

2. A cured positive plate of the battery. 

3. Grid lead electrode. 

4. A cured negative plate of the battery. 

In stirred and un-stirred oxygenated sulphuric acid(0.56M) at 298K. 

3. Investigation of the effect of oxygen and different media on the 

corrosion and passivity of the battery plates. 

4. Study of the thermodynamic quantities (DG, DH and DS) for the 

corrosion of four type of the battery plates. 

5. The kinetic study aspects of the corrosion of the four type of battery 

plates have been investigated and the activation energies and pre- 

exponential factors for the corrosion process have been determined. 

(26)

2.1-The Experimental Set-Up 

This instrument consists of a source of potential (an electronic 

voltmeter) and a current source (68) . The potentiostat measures the potential 

V of the test electrode under study and compares this with the preselected 

value V* from the potential source. 

If there is a difference dV= V*- V between the measured and the 

chosen potentials, potentiastate tells its current source to send a current i 

between the auxiliary and the test electrode. The direction and magnitude 

of this current is electronically chosen to keep the potential of test electrode 

at the desired value, i.e, to make 

dV= V*-V= 0 (69) . 

The experiments on the electrodes in H2SO4 solution were performed 

using a potentiostat of the type PRI 10-0.5L, which was obtained from sole 

Tacussel (France) which had an output voltage of – 10V and output 

current of – 500 mA and a response time of (2-3) ms. 

The potentiostat was connected to a potentiostatic recorder, type EPL- 

2B with an interchangeable plug- in pre-amplifier, type EPRL2, which 

enabled the working electrode current to be recorded in either linear or 

logarithmic coordinates. The potentiostat, which was termed commercially 

as “ corroscript” contained a digital electronic millivoltmeter, type 

MVN79. This instrument is intended for highly accurate potential 

measurements from a few millivolts to some tens of volts, across sources of 

very high resistance, all organized in a particularly way (70) . 

A simple electronic lay-out of the potentiostat is shown 

diagrammatically in Fig. (2-1). The potential of the working electrode , Et, 

is measured against another electrode Er, called reference electrode . A 

third electrode, Ea, called the auxiliary electrode allows the electrical 

(27)

current necessary to produce the desired potential difference to flow 

through the circuit (71) . 

Fig. (2-1): The modern electronic instruments of potentiostate. 

Where : 

Ea = Auxiliary electrode, 

Er = Reference electrode, 

Et = Working electrode. 

The working and the auxiliary electrodes are connected to the output 

terminals of the potentiostat current through the circuit is automatically 

controlled so that the potential difference between the working electrode 

and the reference electrodes takes the desired value. 

This process is carried out by means of a differential amplifier Ad, 

one output of which e1, is connected to the reference electrode and the other 

output, e2, to voltage source called pilot voltage (or control voltage). The 

amplifier derives power, Ap, which controls the output current of the 

potentiostat in such a manner that the potential difference between the 

working electrode and the reference electrode remains equal to the applied 

voltage, Ec. (72) . 

(28)

2.2- The working Electrode 

Seven types of specimens of different working electrodes have been 

examined and these involved: 

1. A spectroscopically standardized lead specimen which was obtained 

from Johnson Matthery Co. Ltd (U.K). 

2. A lead–antimony alloy, containing 2.7 wt % antimony. Such alloy is 

used in Bable factories for industrial synthesis of lead oxide by Barton- 

pot and Ball-Mill methods. 

3. A lead-antimony alloy, containing more than 6% antimony. Such alloy 

is used in Bable factories for industrial preparation of the grids of the 

lead-acid battery plates. 

4. Un-cured negative plate of the battery. This represented a grid, which 

was coated with the paste of the negative plate prior to curing. 

5. Un-cured positive plate of the battery. This represented a grid which 

was coated with the paste of the positive plate and prior to curing stage. 

6. A cured negative plate of step (4). 

7. A cured positive plate of step (5). 

Specimens of the steps (2-7) have been obtained directly from Bable 

factory for manufacturing lead acid storage batteries in Baghdad. 

The working electrode of the corrosion cell was made of plate 

material of the battery (steps 1 to 7). The exposed surface area of the 

material was circular with an apparent area of 1cm 2 . The working electrode 

specimen of plate material was mounted in an appropriate plastic holder so 

that a surface area of 1cm 2 of the plate material remained exposed to the 

test solution (H2SO4) when the Specimen was immersed in such 

solution (70) . 

(29)

2.3- The Auxiliary Electrode 

The auxiliary electrode was prepared from a high purity platinum rod 

stock with an exposed surface area of 1.8cm 2 (73) . 

Platinized auxiliary electrode was used in the experiments due to its 

large surface area and high catalytic activity. Platinization of the electrode 

was made after cleaning the surface of the platinum electrode in hot aqua 

regia (3 parts concentrated HCl and 1 part concentrated HNO3), washing, 

and then drying. The electrode was then platinized by immersion in 

solution consisting 3 percent chloroplatinic acid and 0.02 percent lead 

acetate and electrolyzing at a current density of 40 mA/cm 2 for 5 min (74,75) . 

The polarity was reversed every minute. Occluded chloride was 

removed by electrolyzing in a dilute (10 percent) sulphuric acid solution for 

5 min, with a reversal in polarity every minute. The electrode was 

thereafter rinsed thoroughly and stored in distilled water. The electrode 

which was obtained by this procedure had a longer life and was less 

susceptible to poisoning due to the presence of lead acetate in its surface 

coating (72) . 

(30)

2.4- The Reference Electrode 

A saturated calomel reference electrode (SCE) was used throughout 

the whole work. The calomel electrode consisted of mercury, mercurous 

chloride and chloride ion. 

Pt, Hg(l), Hg2Cl2(s) / Cl - -----(2-1) 

The reduction reaction which occurs in the calomel electrode, may be 

represented as 

(31) 

Hg2Cl2(s) + 2e 2Hg(l) + 2 Cl - 

(aq) 

-----(2-2) 

The electrode is usually brought in contact with the electrolyte 

through a glass tubing as “Luggin Cappillary” which is filled by the test 

solution. The tip of the luggin capillary is placed in the electrochemical cell 

very close to the working electrode through a Luggin Capillary bridge 

which was filled with test solution (72) . 

The Calomel electrode could be prepared by grinding calomel 

(Hg2Cl2), mercury and a small quantity saturated KCl solution together and 

placing the resultant slurry in a layer about 1cm thick on the surface of 

mercury contained in a clean test tube. External contact to the mercury was 

usually made by a platinum wire which was sealed to glass (73) .

2.5-The Corrosion Cell 

The cell was made of Pyrex glass of 1 liter capacity with appropriate 

necks to fit the electrodes (Fig.2-2 ) and to permit the introduction of gas 

inlet and outlet tubes. A 750 ml of the test solution (H2SO4) was transferred 

into the corrosion cell which was immersed in a thermostat at 25 o C 

(–0.01). 

The Luggin Capillary was filled with the test solution. The tip of the 

Luggin capillary was placed as close as possible to the surface of the 

working electrode (70) . About 1 mm apart to minimize the IR drop effect. 

The electrode assembly of the cell was completed and placed in the 

appropriate position. The test solution was purged for 30-60 min with 

oxygen free nitrogen gas (purity 99.9%) at a rate of 150 cm 3 /min to remove 

oxygen from the solution (73) . 

(32)

Gas Inlet 

Gas Outlet 

Working 

Electrode 

(33) 

Auxiliary 

Electrode 

Fig. ( 2-2):- A schematic diagram of the polarization cell. 

Reference 

Electrode

2.6- Potentiostatic Measurement 

The potentiostatic scan started about 1 hour after the electrodes 

immersion in the test solution, beginning at about –2.0V and proceeded 

through to +2.0V versus the saturated calomel electrode. 

The potential scan was fixed at a rate of 0.3 mV min -1 . The potential 

variation was monitered against log(current density) on an x-y recorder. 

The recorder was of EPL series potentiostatic recorder with 

interchangeable plug-in pre-amplifier, type EPL2, which enabled the 

working electrode current density to be recorded in either linear or 

logarithmic coordinates. 

Both the cathodic and anodic curves were obtained with decreasing 

and increasing polarization, and this was repeated several times. The 

polarization curve obtained involved several regions covering the cathodic, 

anodic, passive and transpassive regions. Extensive data could be derived 

from the detailed analysis of each polarization region. Tangents to the 

anodic and cathodic Tafel regions were extrapolated to the point of 

intersection (Fig.2-3) from which both the corrosion current density (ic)and 

corrosion potential (Ec) were determined using the four-point method. (76) 

Cathodic (bc) anodic (bn) Tafel slopes, transfer coefficients (a), polarization 

resistances (Rp) together with other data could be derived from the 

polarization curves. 

The thermodynamic feasibility of the corrosion has been judged from 

the values of the corrosion potentials and of their dependencies on 

temperature. The kinetic parameters were obtained from the corrosion 

current densities and of their dependencies on temperature. 

Data have also been obtained regarding the potentials and current 

densities corresponding to the passive and transpassive regions (73) . 

(34)

Applied Potential, E 

NOBEL 

Et 

EAP 

EPP 

EC 

E 

C 

G 

Transpassive 

ACTIVE ip ic icr 

B 

Fig.(2-3): A typical polarization curve showing Tofel, active-passive 

transition, passive and transpassive regions and their 

corresponding potentials and current densities. 

(35) 

passive 

A 

Log Current Density 

D 

Active-Passive 

Transition 

Active 

Cathodic

2.7- The Experimental Techniques and Procedure 

The investigation was carried out using the standard CORROSCRIPT 

potentiostat (TACUSSEL, France). 

It consisted of the following parts: 

a) A transistorized potentiostat, type PRT. 10.0.5L. 

b) A digital electronic millivoltmeter, type MVN79. 

c) A potentiometer recorder, type EPL-2B. 

The recorder was fitted with a plug-in amplifier, type TILOG101, 

enabling currents to be plotted on either linear or logarithmic 

coordinates (68) . 

A pilot unit, type SYNCHOSCRIPT, was fitted on the right hand side 

panel of the recorder. This unit was basically a 10-turn potentiometer, 

coupled via an electromagnetic clutch to the chart drive shaft. It was used 

to sweep the control potential supplied to the potentiostat, the sweep was 

tied to chart speed with a maximum sensitivity of 100 mv/ cm. By the use 

of an optional driver unit, type DIDT, the sensitivity could be set at 25, 50 

or 100 mv/ cm. 

The experimental procedure which was based on the standard 

reference method for making potentiostatic polarization measurement, 

which was under the jurisdiction of ASTM committee G-1 on corrosion of 

Metals (77) , and involved the following steps: 

1- The specimen was mounted on the electrode holder and was further 

cleaned just, prior to immersion, by degreasing for 5 min in hot 

benzene, followed by acetone. 

2- One liter of the sulphuric acid solution at a given concentration was 

prepared from Bable Battery Manufacturing Company and distilled 

(36)

water. A 750 ml of the desired solution was transferred to the clean test 

cell. 

3- The temperature of the solution was brought to the desired value by 

immersing the test cell in a controlled temperature water both with a 

precision of – 0.1 o C, a temperature regulator called Temp-unit, type 

HAAKE-KT-33, was used. 

4- The platinzed auxiliary electrodes, the Luggin bridge and other 

components were placed in the test cell by the usual procedures (78) the 

tip of the luggin capillary was placed as close as physically possible to 

the surface of the working electrode in the corrosion cell. The Luggin 

bridge was filled with the test solution and temporarily close the center 

opening with a glass stopper. 

5- The solution, prior to immersion of the test specimen, was purged for 

a minimum of 1h with oxygen –free nitrogen gas (purity, 99.9%) at a 

rate of 150 cm 3 /min to remove oxygen from the solution. In some 

experiments, the solution prior to immersion of the test specimen, was 

purged for a minimum of 1h with pure oxygen gas (purity, 99.9%) at a 

rate of 150 cm 3 min. 

In a series of experiments the solution was stirred at a constant rate 

in the range from 200 to 800 rpm. 

6- The potential scan started 1h after the specimen immersion in the acid 

solution, beginning at about –2.0 V and proceeded through to + 2.0V 

versus the saturated calomel electrode (SCE). A potential against log 

(current density) was recorded by x-y recorder at a potential scan rate 

of 0.3V min -1 . 

Selected specimens at the end of the test were taken from the 

corrosion cell, rinsed carefully with distilled water and left to dry in a 

desicator for a bout 6 hour. 

2.8 -The Chemicals 

(37)

Sodium chloride was purum grade, obtained from Fluka, with a 

purity 99.5%. 

Analar grade ferrous sulphate has been obtained from BDH, with 

purity exceeding 99%. 

Fluka. 

Ortho phosphoric acid 90% of 1.84 gm/ml density produced from 

Sulphuric acid solution with specific gravity of 1.4,which was 

obtained from Bable Battery Manufacturing Company . 

(38)

3.1- The Polarization Curves 

Figs. (3.1) to (3.7) show typical polarization curves for the corrosion 

of seven types of lead specimens in 0.56M sulphuric acid at 298K. 

In describing the various parts and regions of the polarization curves, 

the following symbols have been adopted. 

c, for the cathodic Tafel region, 

a, for the anodic Tafel region, 

p, for the passive region, and in cases where two passive regions were 

present symbols p1 and p2 were used, 

b, for the onset of the breaking of the passive layer. 

It is also worthwhile to refer briefly to the processes, which take place 

at various regions as follows: 

c, also for the cathodic Tafel region in which reduction of hydrogen ions 

occurs with subsequent evolution of hydrogen gas on the electrode surface. 

a, also for the anodic Tafel region in which metal dissolution takes place. 

Oxidation of OH - ions may also take place resulting in the evolution of 

oxygen gas. Such a gas may be captured by the surface metal atoms 

resulting in metal oxidation on passivation. 

p, also for the passive region which involves the formation of an oxide 

layer on the metal or the substrate surface. The passive layer may undergo 

a chemical change giving rise to more than one passivity region (p1, p2,…). 

b, also for breaking of the passivity corresponding to the onset of the 

repture of the passive layer resulting in the liberation of the metal and 

oxygen gas. The process is usually accompanied with the evolution of 

oxygen gas. 

Tables (3.1) to (3.14) present values of the corrosion current densities, 

ic(A cm -2 ), corrosion potentials, Ec (volt), passivity current densities, 

ip(A cm -2 ), passivity potentials, Ep (volt), cathodic, bc, and anodic, ba, Tafel 

(39)

slopes (volt decade -1 ), cathodic, αc, and anodic, αa,transfer coefficients and 

polarization resistances, Rp (W cm -2 ) for the polarization of the working 

electrodes in different media in sulphuric acid solution at different 

concentrations, c(mol dm -3 ) in the absence of additive at three temperatures 

in the rang 298-318 K. 

(40)

(41)

(42)

(43)

(44)

3.2- Results of the Polarization Curves 

The corrosion potential (Ec) of a material in a certain medium at a 

constant temperature is a thermodynamic parameter which is a criterion for 

the extent of the corrosion feasibility under the equilibrium potential 

(in opposite sign) of the cell consisting of the working electrode and the 

auxiliary electrode when the rate of anodic dissolution of the working 

electrode material becomes equal to the rate of the cathodic process that 

takes place on the same electrode surface. 

When Ec becomes more negative, the potential of the Galvanic cell 

becomes more positive and hence the Gibbs free energy change (DG) for 

the corrosion process becomes more negative. The corrosion reaction is 

then expected to be more spontaneous on pure thermodynamic ground. 

When the measured value of Ec becomes less negative, the potential of the 

corresponding Galvanic cell becomes less positive, hence the (ΔG) value 

for the corrosion process becomes less negative, and the process is thus less 

spontaneous. 

It is thus shown that Ec value is a measure for the extent of the 

feasibility of the corrosion reaction on purely thermodynamic basis. Values 

of Ec for the different electrode materials in four different media are 

presented in tables (3.1–3.14) and are also plotted as in Figs.(3.8–3.18). 

The corrosion current density (ic) on the other hand is a kinetic 

parameter and represents the rate of corrosion under specified equilibrium 

condition. Any factor that enhances the value of ic results in an enhanced 

value of the corrosion rate (ic) on pure kinetic ground. Tables (3.1 – 3.14) 

and Figs. (3.19- 3.29) give values of ic which have been derived from the 

data of the polarization curves of the different working electrodes in the 

four different corrosion media at different temperatures. 

(45)

Other data have been obtained from the polarization curves which are 

presented in the tables (3.1 – 3.14). These involved the cathodic (bc) and 

anodic (ba) Tafel slopes and the corresponding cathodic (αc) and anodic (αa) 

transfer coefficients. If the polarization curve involves a passivity region, 

then values of the passive potential (Ep) and passive current density (ip) 

may be obtained from the appropriate point in the passivity regions. Values 

of Ep and ip have also been inserted in the data of tables (3.1– 3.14). 

The results of Ec, ic, bc, ba, αc, αa, Ep, and ip which have been derived 

from the polarization curves which have been given in tables (3.1 – 3.14) 

will be further treated and discussed in the subsequent topics. 

(46)

Table(3-1):Values of corrosion current densities, ic(A cm -2 ), corrosion 

potentials, Ec (volt), Passivity current density, ip(A cm -2 ), passivity 

potentials, Ep(volt), cathodic, bc, and anodic, ba, tafel slopes(volt decade -1 ) 

,cathodic, αc, and anodic, αa, transfer coefficients and polarization 

resistance, Rp(W cm -2 ) for polarization of lead alloy working electrode in 

oxygenated sulphuric acid solution at different concentrations, 

c(mol dm -3 ) in the absence of additive . 

C T/K medium ic/10 -4 

0.56M 

0.25M 

0.1M 

0.56M 

0.25M 

0.1M 

298 

-Ec 

ip/10 -5 

(47) 

Ep ba aa -bc ac Rp 

2.75 0.513 7.20 0.820 0.04 1.38 0.16 0.37 53.46 

308 stirred 2.90 0.510 8.20 0.800 0.05 1.16 0.19 0.32 61.98 

318 4.00 0.500 12.00 0.790 0.06 1.04 0.24 0.26 52.71 

298 

2.75 0.520 7.40 0.810 0.04 1.41 0.45 0.13 60.33 

308 stirred 2.80 0.517 7.70 0.800 0.04 1.48 0.48 0.13 59.05 

318 4.00 0.500 9.00 0.770 0.05 1.27 0.54 0.12 49.52 

298 

2.60 0.530 7.00 0.770 0.05 1.16 0.16 0.37 64.52 

308 stirred 2.70 0.510 7.20 0.740 0.06 0.98 0.17 0.36 73.37 

318 3.20 0.500 9.40 0.730 0.06 1.12 0.19 0.34 58.59 

298 

0.65 0.516 7.30 0.610 0.03 1.76 0.43 0.14 207.49 

un- 

308 1.40 0.513 7.80 0.580 0.05 1.23 0.55 0.11 141.75 

stirred 

318 1.70 0.510 8.60 0.560 0.05 1.37 0.84 0.08 111.23 

298 

0.55 0.520 12.00 0.560 0.05 1.09 0.38 0.16 374.74 

un- 

308 1.30 0.510 9.20 0.580 0.05 1.15 0.56 0.11 162.30 

stirred 

318 1.65 0.500 9.40 0.620 0.05 1.18 0.66 0.10 129.94 

298 

0.50 0.510 11.00 0.620 0.05 1.28 0.45 0.13 362.50 

un- 

308 1.20 0.500 11.50 0.600 0.10 0.61 0.59 0.10 308.23 

stirred 

318 1.60 0.480 12.50 0.580 0.11 0.57 0.62 0.10 256.71

Table(3-2):Values of corrosion current densities,ic(A cm -2 ), corrosion 

potentials, Ec (volt),Passivity current density, ip(A cm -2 ),passivity 

potentials, Ep(volt), cathodic, bc, and anodic, ba, tafel slopes (volt 

decade -1 ), cathodic,αc,and anodic, αa,transfer coefficients and polarization 

resistance,Rp(W cm -2 ) for polarization of lead alloy working electrode in 

deaerated sulphuric acid solution at different concentrations, 

c(mol dm -3 )in the absence of additive . 


0.56M 

0.25M 

0.1M 

0.56M 

0.25M 

0.1M 

298 

-Ec 

ip/10 -5 

(48) 

Ep ba αa -bc αc Rp 

7.5 0.518 6.80 1.010 0.07 0.84 0.16 0.36 284.50 

308 stirred 8.1 0.514 7.80 0.910 0.08 0.76 0.16 0.37 289.55 

318 9.5 0.510 8.50 0.750 0.08 0.82 0.20 0.31 254.69 

298 

7.2 0.510 6.20 0.670 0.05 1.29 0.18 0.33 220.76 

308 stirred 8.2 0.506 6.90 0.640 0.07 0.92 0.21 0.30 264.71 

318 9.6 0.500 7.00 0.610 0.12 0.54 0.23 0.27 350.29 

298 

7 0.500 6.00 0.630 0.07 0.79 0.24 0.25 353.36 

308 stirred 7.9 0.490 7.90 0.620 0.12 0.51 0.26 0.23 452.11 

318 8.3 0.480 8.50 0.610 0.15 0.43 0.31 0.20 518.03 

298 

5 0.519 5.70 0.980 0.04 1.47 0.44 0.13 320.66 

un- 

308 6 0.510 9.00 0.930 0.05 1.30 0.22 0.28 279.89 

stirred 

318 10 0.500 9.60 0.900 0.05 1.21 0.45 0.14 202.00 

298 

2.55 0.520 6.00 1.000 0.04 1.34 0.21 0.29 617.43 

un- 

308 4.8 0.510 6.90 0.960 0.06 0.95 0.23 0.26 455.70 

stirred 

318 6 0.500 7.50 0.880 0.07 0.93 0.40 0.16 418.86 

298 

1.65 0.518 6.20 0.780 0.09 0.69 0.47 0.13 1898.48 

un- 

308 4.8 0.510 6.60 0.770 0.09 0.69 0.48 0.13 679.50 

stirred 

318 5.2 0.500 8.00 0.760 0.10 0.63 0.49 0.13 690.42



potentials, Ep(volt), cathodic, bc, and anodic,ba, tafel slopes (volt 

decade -1 ), cathodic, αc, and anodic, αa, transfer coefficients and 

polarization resistance, Rp(W cm -2 ) for polarization of pure lead working 

electrode in oxygenated sulphuric acid solution at different 

concentrations, c(mol dm -3 ) in the absence of additive . 


0.56M 

0.25M 

0.1M 

0.56M 

0.25M 

0.1M 

298 

-Ec 

ip/10 -5 

(49) 


1.85 0.530 12.00 0.860 0.04 1.34 0.22 0.27 85.92 

308 stirred 3 0.519 12.50 0.840 0.04 1.42 0.32 0.19 54.69 

318 3.5 0.513 15.00 0.820 0.06 1.06 0.38 0.17 63.62 

298 

1.65 0.520 4.50 0.790 0.07 0.85 0.21 0.29 136.88 

308 stirred 2.6 0.510 5.00 0.780 0.07 0.90 0.29 0.21 92.21 

318 3.2 0.500 8.70 0.770 0.07 0.86 0.42 0.15 84.88 

298 

1.35 0.500 4.20 0.800 0.05 1.09 0.66 0.09 160.95 

308 stirred 2.4 0.490 4.20 0.760 0.05 1.19 0.84 0.07 87.64 

318 3.2 0.490 5.40 0.750 0.05 1.30 0.69 0.09 61.38 

298 

0.57 0.532 1.60 0.790 0.06 1.06 0.40 0.15 371.88 

un- 

308 1.1 0.526 7.00 0.750 0.06 1.11 0.48 0.13 195.35 

stirred 

318 1.65 0.521 11.00 0.540 0.06 1.13 0.69 0.09 136.11 

298 

0.5 0.510 6.80 0.620 0.06 0.94 0.49 0.12 483.56 

un- 

308 1 0.500 6.90 0.600 0.06 0.97 0.33 0.18 229.62 

stirred 

318 1.4 0.500 7.00 0.590 0.07 0.85 0.25 0.25 177.79 

298 

0.4 0.510 1.20 0.740 0.05 1.10 0.38 0.16 508.97 

un- 

308 1 0.500 8.50 0.680 0.05 1.12 0.39 0.16 207.74 

stirred 

318 1.35 0.500 8.80 0.600 0.05 1.27 0.43 0.15 143.45





polarization resistance, Rp(W cm -2 ) for polarization of pure lead working 

electrode in deaerated sulphuric acid solution at different concentrations, 



0.56M 

0.25M 

0.1M 

0.56M 

0.25M 

0.1M 

298 

-Ec 

ip/10 -5 

(50) 


5.8 0.533 4.7 1.010 0.04 1.38 0.16 0.37 252.55 

308 stirred 7.5 0.530 5.7 0.940 0.04 1.53 0.27 0.22 201.38 

318 20 0.526 7 0.925 0.04 1.51 0.28 0.23 78.98 

298 

4.8 0.520 6.5 0.650 0.07 0.84 0.11 0.52 388.00 

308 stirred 5 0.510 7 0.630 0.10 0.61 0.13 0.48 486.87 

318 7.5 0.500 8 0.610 0.41 0.15 0.15 0.42 632.38 

298 

3.3 0.520 5.5 0.630 0.09 0.69 0.72 0.08 1011.65 

308 stirred 3.5 0.510 6 0.610 0.09 0.66 0.89 0.07 1033.29 

318 7.2 0.500 6.4 0.610 0.21 0.30 0.95 0.07 1035.46 

298 

3.3 0.536 5 1.000 0.11 0.55 0.21 0.29 922.61 

un- 

308 5.6 0.517 6 0.950 0.11 0.54 0.43 0.14 696.82 

stirred 

318 16.5 0.510 6.5 0.810 0.12 0.53 0.45 0.14 247.67 

298 

5 0.510 4.5 0.950 0.05 1.21 0.38 0.16 375.49 

un- 

308 5.4 0.500 4.8 0.870 0.04 1.53 0.44 0.14 293.74 

stirred 

318 8.5 0.510 6 0.920 0.03 1.90 0.66 0.10 161.51 

298 

1.3 0.530 5.1 0.870 0.03 1.71 0.35 0.17 1050.71 

un- 

308 3.8 0.510 6 0.790 0.04 1.65 0.53 0.12 395.89 

stirred 

318 7.4 0.500 6.7 0.710 0.07 0.88 0.54 0.12 370.03





polarization resistance, Rp(W cm -2 ) for polarization of grid lead working 

electrode in deaerated sulphuric acid solution at different concentrations, 



0.56M 

0.25M 

0.1M 

0.56M 

0.25M 

0.1M 

298 

-Ec 

ip/10 -5 

(51) 


10 0.527 6.8 1.080 0.08 0.78 0.21 0.28 241.56 

308 stirred 11 0.521 7.2 0.950 0.09 0.72 0.23 0.26 246.28 

318 14 0.520 7.6 0.920 0.09 0.68 0.24 0.26 207.02 

298 

4.5 0.510 8 0.710 0.07 0.85 0.13 0.47 430.43 

308 stirred 6.5 0.500 9 0.680 0.09 0.66 0.16 0.39 387.60 

318 8 0.500 1 0.640 0.10 0.63 0.16 0.39 334.68 

298 

5.1 0.500 7.5 0.970 0.06 0.91 0.62 0.10 499.76 

308 stirred 6 0.490 7.8 0.840 0.07 0.92 0.75 0.08 441.65 

318 7 0.490 10 0.840 0.10 0.61 0.95 0.07 576.14 

298 

3.7 0.528 7.5 1.070 0.03 1.97 0.15 0.41 291.92 

un- 

308 6 0.515 7.8 0.930 0.03 1.76 0.15 0.39 204.76 

stirred 

318 15 0.500 9 0.900 0.04 1.50 0.15 0.42 94.76 

298 

2.5 0.520 7.3 1.050 0.04 1.33 0.22 0.26 554.15 

un- 

308 7 0.510 8 0.910 0.04 1.58 0.27 0.22 209.73 

stirred 

318 14 0.500 9.2 0.900 0.04 1.47 0.31 0.20 116.91 

298 

2.1 0.510 1.15 1.010 0.06 1.05 0.10 0.61 737.49 

un- 

308 4.5 0.500 8 0.840 0.10 0.59 0.16 0.39 600.80 

stirred 

318 8 0.500 8.5 0.830 0.10 0.65 0.17 0.37 335.67


potentials, Ec (volt),Passivity current density, ip(A cm -2 ), passivity 



polarization resistance, Rp(W cm -2 ) for polarization of grid lead working 

electrode in oxygenated sulphuric acid solution at different 



0.56M 

0.25M 

0.1M 

0.56M 

0.25M 

0.1M 

298 

-Ec 

ip/10 -5 

(52) 


2.6 0.521 75 0.920 0.06 0.95 0.30 0.19 86.32 

308 stirred 3.5 0.510 91 0.890 0.04 1.42 0.59 0.10 49.62 

318 5 0.500 96 0.850 0.06 1.07 0.67 0.09 46.86 

298 

2.4 0.500 5.7 0.950 0.07 0.91 0.17 0.35 85.32 

308 stirred 3.3 0.490 6 0.810 0.05 1.29 0.25 0.24 52.58 

318 4.2 0.500 6.5 0.780 0.11 0.58 0.54 0.12 93.50 

298 

2.2 0.500 5.8 0.890 0.07 0.90 0.21 0.29 98.35 

308 stirred 3 0.500 6.5 0.820 0.08 0.81 0.36 0.17 90.04 

318 3.5 0.500 7 0.800 0.09 0.73 0.62 0.10 94.13 

298 

0.63 0.523 7.5 0.970 0.05 1.15 0.50 0.12 321.49 

un- 

308 0.95 0.510 8 0.890 0.05 1.30 0.54 0.11 198.05 

stirred 

318 1.3 0.510 8 0.850 0.05 1.33 0.59 0.11 146.67 

298 

5 0.520 9.5 0.860 0.05 1.19 0.30 0.20 371.15 

un- 

308 9 0.500 10 0.790 0.19 0.33 0.49 0.12 651.78 

stirred 

318 15 0.500 11 0.600 0.29 0.22 0.75 0.08 618.31 

298 

7.5 0.500 6.3 0.910 0.06 0.92 0.27 0.22 301.45 

un- 

308 8.8 0.490 7.5 0.790 0.06 1.04 0.33 0.18 247.20 

stirred 

318 15 0.480 11.5 0.780 0.06 1.14 0.38 0.17 139.76





polarization resistance, Rp(W cm -2 ) for polarization of cured negative 

working electrode in deaerated sulphuric acid solution at different 



0.56M 

0.25M 

0.1M 

0.56M 

0.25M 

0.1M 

298 

-Ec 

ip/10 -3 

(53) 


1.2 0.474 5 0.810 0.05 1.31 0.34 0.18 1.65 

308 stirred 1.1 0.470 5.2 0.800 0.05 1.35 0.34 0.18 1.58 

318 1.35 0.480 5.5 0.770 0.05 1.33 0.38 0.17 1.35 

298 

1.05 0.510 2.2 0.760 0.08 0.72 0.15 0.40 2.18 

308 stirred 1 0.500 3.2 0.740 0.09 0.69 0.24 0.25 2.81 

318 1.1 0.500 3.25 0.740 0.09 0.68 0.29 0.22 2.76 

298 

0.375 0.520 2.75 0.770 0.05 1.22 0.17 0.34 4.38 

308 stirred 0.42 0.510 2.8 0.750 0.07 0.91 0.31 0.20 5.70 

318 0.525 0.510 3 0.730 0.07 0.96 0.38 0.17 4.64 

298 

1.1 0.478 4.8 0.780 0.05 1.25 0.17 0.35 1.61 

un- 

308 1.55 0.470 5 0.760 0.08 0.73 0.20 0.31 1.66 

stirred 

318 1.6 0.470 5.6 0.740 0.08 0.80 0.21 0.31 1.54 

298 

1 0.520 2.75 0.770 0.07 0.83 0.22 0.27 2.35 

un- 

308 1.4 0.520 3 0.740 0.08 0.80 0.31 0.20 1.90 

stirred 

318 1.5 0.510 3.5 0.720 0.09 0.72 0.43 0.15 2.10 

298 

0.45 0.500 2.9 0.770 0.05 1.09 0.27 0.22 4.38 

un- 

308 0.5 0.500 3.2 0.780 0.05 1.13 0.27 0.22 3.93 

stirred 

318 0.61 0.500 3.5 0.750 0.09 0.74 0.30 0.21 4.71





polarization resistance, Rp(W cm -2 ) for polarization of cured negative 

working electrode in oxygenated sulphuric acid solution at different 



0.56M 

0.25M 

0.1M 

0.56M 

0.25M 

0.1M 

298 

-Ec 

ip/10 -3 

(54) 


3 0.471 7.2 0.760 0.08 0.70 0.17 0.35 0.82 

308 stirred 3.3 0.470 8.5 0.800 0.08 0.81 0.20 0.31 0.72 

318 3.5 0.470 9.8 0.790 0.08 0.77 0.24 0.26 0.76 

298 

1.3 0.520 3 0.760 0.10 0.59 0.14 0.44 1.92 

308 stirred 1.4 0.520 2.5 0.750 0.10 0.61 0.20 0.30 2.06 

318 1.5 0.510 2.8 0.740 0.11 0.57 0.21 0.31 2.07 

298 

1.1 0.500 2.9 0.730 0.14 0.42 0.24 0.25 3.52 

308 stirred 1 0.500 3 0.730 0.14 0.45 0.25 0.24 3.82 

318 1.5 0.500 3.4 0.690 0.14 0.45 0.26 0.24 2.65 

298 

1.65 0.473 6.2 0.800 0.09 0.64 0.08 0.72 1.14 

un- 

308 3 0.470 6.5 0.760 0.09 0.66 0.11 0.57 0.72 

stirred 

318 3.2 0.470 9 0.740 0.10 0.63 0.11 0.58 0.70 

298 

1.1 0.500 1.2 0.780 0.07 0.84 0.10 0.59 1.63 

un- 

308 1.15 0.500 1.5 0.750 0.07 0.92 0.11 0.56 1.56 

stirred 

318 2.1 0.500 2.7 0.730 0.07 0.95 0.10 0.61 0.83 

298 

0.8 0.510 3.5 0.790 0.10 0.57 0.05 1.27 1.74 

un- 

308 0.85 0.510 4.25 0.810 0.10 0.64 0.11 0.54 2.65 

stirred 

318 9 0.500 6.5 0.770 0.10 0.63 0.31 0.20 3.64



potentials, Ep(volt),cathodic, bc, and anodic, ba, tafel slopes (volt 


polarization resistance, Rp(W cm -2 ) for polarization of cured positive 


concentrations, c (mol dm -3 ) in the absence of additive . 


0.56M 

0.25M 

0.1M 

0.56M 

0.25M 

0.1M 

298 

-Ec 

ip/10 -3 

(55) 


1.1 0.487 4.5 0.800 0.04 1.31 0.21 0.28 1.46 

308 stirred 1.3 0.485 6.5 0.770 0.05 1.31 0.22 0.28 1.29 

318 1.6 0.480 6.5 0.760 0.05 1.32 0.24 0.26 1.08 

298 

0.85 0.520 4 0.800 0.06 1.02 0.13 0.45 2.05 

308 stirred 0.9 0.510 4.9 0.780 0.06 1.11 0.19 0.32 2.06 

318 0.93 0.500 5 0.770 0.06 1.07 0.19 0.33 2.10 

298 

0.35 0.510 3.5 0.810 0.04 1.33 0.24 0.25 4.65 

308 stirred 0.4 0.510 3.7 0.800 0.05 1.33 0.27 0.23 4.26 

318 0.4 0.510 4.2 0.700 0.06 1.05 0.30 0.21 5.42 

298 

1 0.489 6.5 0.790 0.04 1.33 0.19 0.31 1.74 

un- 

308 2.4 0.484 6.8 0.780 0.04 1.42 0.22 0.28 0.65 

stirred 

318 2.5 0.480 7 0.760 0.04 1.44 0.26 0.24 0.65 

298 

0.75 0.520 5.8 0.780 0.05 1.24 0.08 0.72 1.74 

un- 

308 2 0.500 6.2 0.740 0.06 1.06 0.12 0.50 0.85 

stirred 

318 2 0.510 7 0.710 0.06 1.03 0.43 0.15 1.17 

298 

0.57 0.500 4.5 0.790 0.05 1.13 0.19 0.31 3.09 

un- 

308 0.6 0.500 4.7 0.770 0.06 1.01 0.22 0.28 3.44 

stirred 

318 0.85 0.500 5.1 0.730 0.06 1.02 0.23 0.27 2.48





polarization resistance, Rp(W cm -2 ) for polarization of cured positive 




0.56M 

0.25M 

0.1M 

0.56M 

0.25M 

0.1M 

298 

-Ec 

ip/10 -3 

(56) 


2.3 0.482 7 0.780 0.07 0.87 0.08 0.76 0.68 

308 stirred 3.5 0.480 8.5 0.770 0.11 0.57 0.10 0.59 0.65 

318 3.7 0.480 8.8 0.750 0.08 0.76 0.05 1.22 0.37 

298 

1.2 0.510 2.4 0.790 0.07 0.84 0.06 0.92 1.21 

308 stirred 1.2 0.510 2.75 0.740 0.07 0.87 0.12 0.53 1.58 

318 1.4 0.500 3 0.740 0.11 0.57 0.20 0.32 2.19 

298 

0.9 0.500 3.25 0.760 0.10 0.59 0.09 0.63 2.33 

308 stirred 1.2 0.500 4 0.740 0.10 0.61 0.15 0.42 2.15 

318 1.35 0.500 4 0.720 0.12 0.54 0.18 0.34 2.30 

298 

1.6 0.485 3.7 0.780 0.08 0.71 0.08 0.72 1.13 

un- 

308 1.7 0.480 4.1 0.770 0.10 0.59 0.09 0.67 1.24 

stirred 

318 1.9 0.480 5.5 0.750 0.10 0.64 0.09 0.69 1.08 

298 

1.1 0.500 4.75 0.780 0.08 0.76 0.09 0.68 1.62 

un- 

308 1.5 0.510 5 0.750 0.08 0.81 0.13 0.48 1.37 

stirred 

318 1.5 0.500 5 0.740 0.09 0.73 0.14 0.44 1.55 

298 

0.95 0.500 5.2 0.770 0.09 0.69 0.11 0.52 2.23 

un- 

308 0.65 0.500 5.6 0.730 0.09 0.71 0.12 0.52 3.33 

stirred 

318 1.2 0.500 5.75 0.720 0.14 0.45 0.15 0.43 2.61




decade -1 ), cathodic, αc, and anodic,aa,transfer coefficients and 

polarization resistance, Rp(W cm -2 ) for polarization of uncured positive 




0.56M 

0.25M 

0.1M 

0.56M 

0.25M 

0.1M 

298 

-Ec 

ip/10 -3 

(57) 


6.6 0.506 3.4 0.790 0.07 0.83 0.24 0.25 3.61 

308 stirred 7.8 0.500 2.25 0.750 0.07 0.83 0.25 0.25 3.15 

318 8.5 0.500 2.5 0.660 0.08 0.84 0.30 0.21 3.07 

298 

3 0.510 2.25 0.740 0.07 0.80 0.28 0.21 8.49 

308 stirred 4 0.500 2.3 0.720 0.08 0.80 0.31 0.20 6.67 

318 7 0.510 2.4 0.710 0.08 0.84 0.33 0.19 3.81 

298 

1.2 0.510 1.75 0.770 0.06 1.04 0.14 0.44 14.45 

308 stirred 1.6 0.500 1.9 0.740 0.06 0.95 0.23 0.26 13.65 

318 2.75 0.510 2 0.710 0.07 0.89 0.23 0.27 8.63 

298 

5.4 0.509 2.6 0.780 0.04 1.44 0.15 0.40 2.58 

un- 

308 9.5 0.500 2.75 0.770 0.05 1.35 0.33 0.18 1.82 

stirred 

318 12 0.505 3.2 0.760 0.05 1.30 0.34 0.18 1.54 

298 

2.1 0.510 1.7 0.740 0.11 0.52 0.27 0.22 16.66 

un- 

308 6.6 0.510 2.25 0.750 0.11 0.58 0.35 0.17 5.36 

stirred 

318 6.25 0.510 2.4 0.690 0.11 0.56 0.45 0.14 6.24 

298 

2 0.500 1.9 0.740 0.04 1.34 0.23 0.25 8.04 

un- 

308 2.75 0.500 2 0.740 0.06 0.97 0.33 0.18 8.35 

stirred 

318 5.75 0.510 2.35 0.700 0.17 0.37 0.93 0.07 10.88





polarization resistance, Rp(W cm -2 ) for polarization of uncured positive 




0.56M 

0.25M 

0.1M 

0.56M 

0.25M 

0.1M 

298 

-Ec 

ip/10 -3 

(58) 


2.1 0.500 3.4 0.780 0.03 2.05 0.18 0.34 0.51 

308 stirred 2.25 0.500 4.5 0.770 0.04 1.37 0.31 0.20 0.75 

318 2.4 0.500 5 0.760 0.05 1.27 0.17 0.37 0.70 

298 

0.93 0.510 3 0.770 0.06 1.03 0.10 0.59 1.70 

308 stirred 1 0.500 3.4 0.750 0.06 1.08 0.31 0.20 2.07 

318 1.1 0.500 3.4 0.730 0.06 1.08 0.33 0.19 1.96 

298 

0.17 0.520 2 0.740 0.05 1.08 0.32 0.18 11.93 

308 stirred 0.26 0.510 2.25 0.720 0.05 1.14 0.45 0.14 7.98 

318 0.46 0.500 2.25 0.730 0.07 0.92 0.51 0.12 5.72 

298 

2 0.502 4.25 0.790 0.07 0.85 0.12 0.48 0.97 

un- 

308 2.5 0.500 5 0.780 0.07 0.85 0.22 0.28 0.94 

stirred 

318 2.6 0.500 5.5 0.720 0.08 0.80 0.61 0.10 1.17 

298 

0.82 0.500 2.5 0.730 0.12 0.48 0.20 0.30 3.99 

un- 

308 2.35 0.503 3.5 0.730 0.13 0.47 0.22 0.27 1.51 

stirred 

318 2.55 0.500 3.6 0.720 0.14 0.45 0.23 0.27 1.48 

298 

0.7 0.520 2 0.750 0.09 0.63 0.18 0.33 3.82 

un- 

308 1.15 0.520 2.5 0.700 0.10 0.63 0.21 0.29 2.50 

stirred 

318 1.5 0.510 2.5 0.680 0.14 0.47 0.27 0.24 2.60



potentials, Ep(volt),cathodic, bc, and anodic, ba, tafel slopes (volt 


polarization resistance, Rp(W cm -2 ) for polarization of uncured negative 




0.56M 

0.25M 

0.1M 

0.56M 

0.25M 

0.1M 

298 

-Ec 

ip/10 -3 

(59) 


2 0.492 4.5 0.770 0.06 0.94 0.11 0.52 0.88 

308 stirred 2.4 0.490 5.3 0.810 0.07 0.89 0.13 0.47 0.82 

318 2.7 0.488 6.5 0.780 0.07 0.89 0.16 0.40 0.79 

298 

1.3 0.530 1.35 0.810 0.11 0.55 0.11 0.52 1.86 

308 stirred 2 0.530 1.75 0.750 0.11 0.54 0.12 0.49 1.28 

318 2.6 0.520 1.9 0.740 0.13 0.48 0.16 0.38 1.22 

298 

0.95 0.520 1.25 0.780 0.11 0.56 0.13 0.46 2.65 

308 stirred 1.1 0.500 1.25 0.770 0.12 0.52 0.15 0.42 2.57 

318 1.25 0.500 6.5 0.720 0.14 0.46 0.16 0.41 2.53 

298 

1.25 0.493 3.4 0.770 0.07 0.87 0.08 0.71 1.30 

un- 

308 1.3 0.500 3.9 0.760 0.09 0.66 0.10 0.61 1.60 

stirred 

318 1.46 0.490 5 0.750 0.09 0.73 0.13 0.50 1.53 

298 

1.22 0.530 2 0.790 0.10 0.59 0.10 0.59 1.77 

un- 

308 1.28 0.520 2.25 0.770 0.13 0.46 0.10 0.61 1.93 

stirred 

318 1.4 0.500 2.5 0.750 0.14 0.44 0.11 0.55 1.97 

298 

0.87 0.500 2.3 0.790 0.11 0.52 0.11 0.52 2.82 

un- 

308 1 0.510 3.2 0.760 0.13 0.48 0.12 0.50 2.70 

stirred 

318 1.25 0.510 5.5 0.740 0.15 0.41 0.12 0.53 2.33





polarization resistance, Rp(W cm -2 ) for polarization of uncured negative 




0.56M 

0.25M 

0.1M 

0.56M 

0.25M 

0.1M 

298 

-Ec 

ip/10 -3 

(60) 


1.05 0.495 4.25 0.770 0.05 1.16 0.15 0.39 1.38 

308 stirred 1.9 0.495 4.9 0.760 0.05 1.14 0.19 0.33 0.95 

318 2.2 0.490 5.5 0.730 0.07 0.96 0.25 0.26 1.02 

298 

0.55 0.510 32 0.750 0.07 0.90 0.09 0.67 2.97 

308 stirred 0.7 0.520 37.5 0.730 0.07 0.84 0.14 0.45 2.92 

318 0.82 0.530 39 0.700 0.07 0.85 0.33 0.19 3.21 

298 

0.53 0.510 2.2 0.780 0.06 0.98 0.14 0.44 3.42 

308 stirred 0.6 0.510 2.85 0.770 0.06 0.97 0.17 0.36 3.32 

318 0.7 0.510 3.25 0.690 0.08 0.82 0.26 0.24 3.70 

298 

0.9 0.497 4.1 0.760 0.08 0.76 0.10 0.58 1.73 

un- 

308 2.75 0.491 3.8 0.800 0.08 0.74 0.11 0.57 0.74 

stirred 

318 2.7 0.490 4.5 0.770 0.08 0.77 0.15 0.42 0.86 

298 

1.1 0.510 2.85 0.780 0.07 0.87 0.13 0.47 1.75 

un- 

308 1.5 0.510 3.1 0.780 0.07 0.86 0.16 0.38 1.42 

stirred 

318 1.6 0.500 4.1 0.740 0.08 0.81 0.31 0.20 1.68 

298 

1 0.520 2.5 0.790 0.08 0.71 0.09 0.68 1.85 

un- 

308 1.2 0.510 2.8 0.770 0.09 0.65 0.27 0.23 2.53 

stirred 

318 1.4 0.500 4 0.760 0.09 0.72 0.38 0.17 2.20

3.2.1- Corrosion Potentials (Ec) 

The results of Figs.(3.8-3.14) indicate that the sequence for the 

increasing negativity of the Ec values for the corrosion of the various 

working electrodes in the four different corrosion media was as: 

4 > 3 > 2 >1 

where the numbers refer to the different corrosion media: 

1. for stirred oxygenated 0.56 M sulphuric acid, 

2. for un-stirred oxygenated acid solution, 

3. for stirred deaerated acid solution, and , 

4. for un-stirred deaerated acid solution. 

Thus, the corrosion attack on the different working electrodes was 

relatively more feasible on thermodynamic ground in un-stirred deaerated 

acid solution and less feasible in stirred oxygenated acid solution. The 

stirring and oxygenation of the acid solution may result in the formation of 

a protective passive oxide layer with ultimate depression of the 

thermodynamic feasibility for corrosion. 

The results of Figs.(3.15-3.18) present different working electrode 

materials in the four different corrosion media. It is shown from the results 

of these figures that the sequence for the decreasing corrosion feasibilities 

in each medium was as: 

2 > 3 > 1> 4> 6> 5> 7 

where the numbers stand for: 

1,lead alloy working electrode, 

2,Grid lead, 

3,Pure lead, 

4,Uncured positive electrode, 

5,Cured positive electrode, 

6,Uncured negative electrode, and , 

7,Cured negative electrode. 

(61)

The grid lead showed greatest tendency for corrosion while the cured 

negative electrode material had the least tendency. Curing of the positive or 

the negative electrodes reduces its tendency for corrosion. The curing on 

the other hand had greater influence on the reduction of the corrosion 

tendency with negative electrode as compared with the positive electrode. 

The lead alloy had less corrosion tendency in any corrosion medium than 

grid lead. Pure lead on the other hand greater corrosion tendency than lead 

alloy. 

(62)

(63)

(64)

(65)

(66)

(67)

(68)

3.2.2- Corrosion Current Densities (ic) 

Values of ic represent the corrosion rates of the working electrode 

material in the sulphuric acid solution at a constant temperature. The results 

of Figs.(3.19-3.25) indicate that the corrosion rates of all the electrode 

materials were highest in stirred oxygenated solution and lowest in unstirred 

deaerated acid solution. The electrode materials differed in their 

corrosion rates in un-stirred oxygenated and stirred deaerated media. The 

largest corrosion rate in stirred oxygenated solution may be accounted for 

on the basis of the greater reactivity of the material surface towards 

oxygen. On the contrary, the smallest corrosion rate in un-stirred deaerated 

medium is expected when the corrosion medium is de-oxygenated (or 

deaerated). 

The behaviours of the various electrode materials in each of the four 

corrosion media may also be compared with the aid of the Figs.(3.26-3.29). 

The corrosion rates of the materials in each medium may be presented in 

the following four sequences: 

sequence (1)- in stirred oxygenated acid solution (Fig. 3.26):- 

7 > 5 > 4 > 6 > 1 > 3 >2 

sequence (2)- in un-stirred oxygenated acid solution (Fig. 3.27):- 

4 > 7 > 5 > 6 > 1 > 3 >2 

sequence (3) – in stirred deaerated acid solution (Fig. 3.28):- 

7 > 5 > 6 > 4 > 3 >1 > 2 

sequence (4)- in un-stirred deaerated acid solution (Fig. 3.29):- 

7 > 5 > 6 > 4 > 1 > 3 > 2 

The largest corrosion rate was with cured negative electrode material 

in stirred oxygenated and in stirred and un-stirred deaerated acid solution, 

and with uncured positive electrode material in un-stirred oxygenated 

solution. The lowest corrosion rate was attained in all the four different 

corrosion media with grid lead material. 

(69)

(70)

(71)

(72)

(73)

(74)

(75)

3.2.3- Passive Potentials (Ep) 

Passivity is an unusual phenomenon observed during the corrosion of 

certain metals and alloys, it can be defined as a loss of chemical reactivity 

under certain environmental conditions (79) . 

Tables (3.1) to (3.14) show values of Ep in each case for the different 

working electrodes in the absence of additives decreased with increasing 

temperature in the four different corrosion media. 

The sequence of the decreasing Ep values for the different working 

electrodes in stirred oxygenated 0.56 M H2SO4 solution was as following: 

2 > 3 > 1 > 4 > 5 > 6 >7 

and in un-stirred oxygenated 0.56 M H2SO4 solution was as: 

2 > 1 > 7 > 4 > 3 > 5 > 6 

in stirred deaerated acid solution the sequence was as: 

2 > 3 > 1 > 7 > 5 > 4 > 6 

and in un-stirred acid solution the sequence was as: 

2 > 3 > 1 > 5 > 4 > 7 > 6 

The largest passive potential was acquired in all the four different 

corrosion media with grid lead material. The lowest passive potentials were 

attained in stirred and un-stirred deaerated and un-stirred oxygenated acid 

solution with uncured negative electrode, and with cured negative in 

stirred oxygenated acid solution. 

The passive potentials of a passive film on a metal or alloy depend 

upon the nature of the metal or the alloy, it becomes more or less positive 

depending on the stability of the existing oxide film. The presence of 

certain anions destroys the passivity and results in localized corrosion (80)(81) . 

(76)

3.2.4 – Passive Current Densities (ip) 

Values of ip represent the passive current densities of the working 

electrode material in the sulphuric acid solution at a constant temperature. 

The behaviours of the various electrode materials in each of the four 

corrosion media may also be compared with the aid of the tables (3.1) to 

(3.14). The passive current densities of the working electrodes in each 

medium may be presented in the following four sequences: 

sequence (1)- in stirred oxygenated acid solution: 

7 > 5> 6> 4> 2> 1> 3 

sequence (2)- in un-stirred oxygenated acid solution: 

7 > 4 > 5 > 6 > 3 > 1 > 2 

sequence (3)- in stirred deaerated acid solution: 

7 > 5 > 6 > 4 > 3 > 1> 2 

sequence (4)- in un-stirred deaerated acid solution: 

4 > 6 > 7 > 5 > 3 > 1 >2 

The largest passive current density was obtained with cured negative 

electrode material in stirred and un-stirred oxygenated and in stirred 

deaerated acid solution, and also with uncured positive electrode material 

in un-stirred deaerated acid solution. The lowest passive current density 

was obtained with grid lead electrode in stirred and un-stirred deaerated 

and in un-stirred oxygenated acid solution, and also with pure lead 

electrode material in stirred oxygenated acid solution. 

The decreasing passive current density(ip) for the electrodes in each 

sequence may be connected with the increasing stability of the oxide 

films, while the increasing in ip for implies a decrease in the stability of the 

oxide film which tends to dissociate at and close to the transpassive 

potential (82) . 

(77)

3.3-Tafel Slopes and Transfer Coefficients 

Values of the transfer coefficients for the cathodic (ac) and anoxic 

(aa) processes have been calculated from the corresponding cathodic (bc) 

and anodic (ba) Tafel slopes using the relationships (83)(84) : 

c 

2. 

303RT 

= 

b F 

a ---- (3.1) 

a 

c 

2. 

303RT 

= 

b F 

a ---- (3.2) 

a 

Tables (3.1) to (3.14) show the cathodic (bc) and anodic (ba) Tafel 

slopes which are obtained from the polarization curves for the corrosion of 

the electrode materials in deaerated and oxygenated solution of the 

different sulphuric acid concentrations and temperatures. 

Values of Tafel slopes (ba or bc) for the both anodic and cathodic 

reactions were generally close to 0.120 V decade-1 and the corresponding 

values of the transfer coefficients (aa and ac) were close to 0.5. The main 

exception to this result was the relatively some higher or lower values of 

the Tafel slopes (ba and bc) or of the transfer coefficients (aa and ac) for 

certain specimens in sulphuric acid solutions. Increasing the temperature 

from 298 to 318 K caused only a slight change in the values of ba and bc. 

A value of the cathodic transfer coefficient (ac) of @ 0.5, or of the 

cathodic Tafel slope of –0.120V decade -1 , may be diagnostic of a proton 

discharge-chemical desorption mechanism in which the proton discharge is 

the rate- determining step (r.d.s). 

The two basic reactions paths for the hydrogen evolution reaction are: 

H3O + (bulk solution) H3O + diffusion 

(metal / solution interface) ---- (3.3) 

which is followed by the discharge step (D): 

H3O + D 

+ M + e M – H + H2O ----(3.4) 

(78)

where M is the metal electrode and M-H represents a hydrogen atom which 

is adsorbed on the metal surface. The discharge (D) step is usually 

followed by a chemical desorption (C-D) step as: 

C-D 

M-H + M-H 2M + H2 .…(3.5) 

in which two adjacent adsorbed hydrogen atoms unite together to form one 

molecule of gaseous hydrogen. If the chemical desorption is the rate- 

determining step, the rate would be independent of the overpotential since 

no charge transfer occurs in such a step and the rate becomes directly 

proportional to the concentration or the coverage (q) of adsorbed hydrogen 

atoms. On the other hand, if the discharge process is followed by a rate- 

determining step involving chemical desorption, the expected value of a 

should be 2.0. 

In some cases, the previous two steps (D) and (C.D) may unite 

together to form one electrochemical desorption (E.D) step as: 

M-H + H3O + + 

E-D 

M(electrode) 2M + H2 + H2O .…(3.6) 

When electrochemical desorption becomes the rate-determining step 

for hydrogen evolution reaction on the casthode, the expected value of a 

will be 1.5. 

The results of the tables (3.1-3.14) indicate that the variation of the 

Tafel slopes and of the corresponding transfer coefficients could be 

interpreted in terms of the variation in the nature of the rate-determining 

step from charge transfer process to either chemical–desorption or to 

electrochemical desorption. 

The variation of the anodic Tafel slopes (ba), or of the anodic transfer 

coefficient (aa), as shown in tables (3.1-3.14) may be attributed to the 

variation of the rate-determining step throughout the metal dissolution 

reaction (85)(86) . 

Two mechanisms have been proposed for the formation of precursor 

passive film on the materials. The first is the precipitation-oxidation 

(79)

mechanism and the second is the solid state mechanism, the latter 

mechanism would not be mass transfer affected, but would account for the 

formation of the precursor film (87)(88) . 

3.4- Polarization Resistance 

The polarization resistance, Rp, of according electrode is defined as 

the slope of a potential (E)-current density (i) plot of the corrosion potential 

(Ec) as : 

h 

Rp = ( ) T , C at h fi 0 

i 

(80) 

---- (3.7) 

where h =E-Ec, is the extent of polarization of the corrosion potential 

and i is the current density (c.d.) corresponding to a particular value of h. 

From the polarization resistance, Rp the corrosion current density (c.d) ic 

can be calculated as: 

ic = 

b 

----(3.8) 

R p 

where b is a combination of the anodic and cathodic Tafel slopes (ba, 

bc) as (89)(90) : 

babc 

= 

2. 303( 

ba 

+ bc 

) 

b ---- (3.9) 

For the general case, by inserting equation (3.8) into equation (3.9) 

one obtains the so-called the stern-Geary equation (91) : 

R 

p 

babc 

2. 303( 

ba 

+ bc 

) i 

= ----(3.10) 

The results of tables (3.1) to (3.14) show that the polarization 

resistance for the corrosion of the working electrodes in an un-stirred 

sulphuric acid solution is greater than its values in the stirred sulphuric 

acid solution indicating an increase in the resistance o the interface in the 

absence of stirring. 

c

In general, the polarization resistance (Rp) decreased with increasing 

sulphuric acid concentration, and Rp values of the first three types of the 

working electrodes were greater than for the other working electrodes as 

given in tables (3.1) to (3.14). 

The polarization resistance (Rp) of the materials in each medium may 

be presented in the following four sequences: 

sequence (1)- in stirred oxygenated acid solution 

2 > 3 > 1> 6 > 7 > 5 > 4 

sequence (2)- in un-stirred oxygenated acid solution 

3 > 2 > 1 > 6 > 7 > 5 > 4 

sequence (3)- in stirred deaerated acid solution 

1 > 3 > 2 > 4 > 7 > 5 > 6 

sequence (4)- in un-stirred deaerated acid solution 

3 > 1 > 2 > 4 > 5 > 6 > 7 

The largest polarization resistance was obtained with pure lead 

electrode in un-stirred oxygenated and in deareated acid solution, and with 

lead alloy electrode in stirred deaerated acid solution and also with grid 

lead in stirred oxygenated acid solution. The lowest polarization 

resistance was obtained with uncured positive electrode in stirred and in 

un-stirred oxygenated acid solution and also with uncured negative 

electrode in stirred deaerated acid solution and also with cured negative in 

un-stirred deaerated acid solution. 

(81)

3.5- Thermodynamics of Corrosion 

When a metal undergoes corrosion there is a change in Gibbs free 

energy, DG, of the system, which is equal to the work associated with the 

corrosion reaction. The performance of such a work is accompanied usually 

by a decrease in the Gibbs free energy of the system, (-DG) (20) . 

If the metal tends to corrode, the work done ( the free energy change 

of the corrosion process) may be expressed in terms of the corrosion 

potential, Ec using the equation: 

DG = - n FEc --- (3.11) 

where F is the Faraday constant and n is the number of electrons involved 

the corrosion reaction. 

The equation indicates that the free energy change is directly measurable 

from electrochemical corrosion potential determination. From the value of 

DG at several temperatures, the change in the entropy (DS) of the corrosion 

could be derived according to the thermodynamic relation: 

-d(DG) / dT = DS ---- (3.12) 

Values of DG are usually plotted against temperature (T); thus at any 

temperature (T) the value of -d(DG) / dT is equal to DS which corresponds 

the slope of the -DG versus T plot at a constant temperature. 

The change in the free energy, DG, is related to DH, the change in the 

enthalpy, and DS, the change in entropy, of the corrosion reaction at a 

constant temperature, T, by the equation (72) : 

DG = DH - TDS ---- (3.13) 

Tables (3.15) to (3.21) give values of the thermodynamics quantities 

DG, DH and DS for the corrosion of all the working electrodes and indicate 

that the values of DG and DH in the un-stirred oxygenated 0.56 M H2SO4 

(82)

solution are more negative than the corresponding values in stirred 

oxygenated 0.56 M H2SO4 solution while DS was more positive. 

The more negative DG values implies generally a greater corrosion 

feasibility on thermodynamic ground, while DH values indicate exothermic 

or endothermic nature of the corrosion reaction. 

The Gibbs free energies obtained for working electrodes, in stirred 

and un-stirred oxygenated 0.56M H2SO4 solution as shown in tables 

(3.15 –3.21) may be arranged in more negativity as in the sequence: 

2 > 3 > 1 > 4 > 6 > 5 > 7 

The sequence shows that the more corrosion feasibility was obtained 

with grid lead electrode of more negative DG value, while the less 

corrosion feasibility was obtained with the cured negative electrode, which 

had less negative value of DG. 

(83)

Table(3-15):Values of the thermodynamics quantities -ΔG, ΔH 

(k J mol -1 ) and ΔS(J mol -1 K -1 )for the corrosion of the lead alloy 

working electrode in (0.56M) oxygenated H2SO4 solution in the 

absence of additives. 

Electrode T/K medium -ΔG ΔH ΔS 

lead alloy 

1 

298 

308 stirred 98.42 -59.80 98.23 

(84) 

99.00 -61.63 98.80 

318 96.49 -56.62 96.32 

298 

99.58 -53.57 99.40 

308 un-stirred 98.42 -50.87 98.26 

318 96.49 -47.39 96.34 

Table(3-16):Values of the thermodynamics quantities -ΔG,ΔH 

(k J mol -1 ) and ΔS(J mol -1 K -1 )for the corrosion of the grid lead 




lead grid 

2 

298 

100.68 -53.41 100.63 

308 stirred 100.16 -49.65 100.00 

318 99.00 -46.85 98.86 

298 

101.72 -70.96 101.45 

308 un-stirred 101.51 -68.74 101.29 

318 100.55 -66.71 100.34


(k J mol -1 ) and ΔS(J mol -1 K -1 )for the corrosion of the pure lead 




pure lead 

3 

298 

308 stirred 99.39 -66.71 99.17 

(85) 

100.55 -68.93 100.32 

318 98.42 -64.68 98.22 

298 

100.93 -80.82 100.66 

308 un-stirred 100.35 -79.56 100.10 

318 99.58 -78.12 99.34 


(k J mol -1 ) and ΔS(J mol -1 K -1 )for the corrosion of the uncured 

positive working electrode in (0.56M) oxygenated H2SO4 solution in 

the absence of additives. 


Uncured 

Positive 

4 

298 

98.42 -69.67 98.19 

308 stirred 97.46 -67.74 97.24 

318 96.49 -65.81 96.29 

298 

96.88 -91.13 96.57 

308 un-stirred 96.49 -90.55 96.20 

318 96.49 -90.36 96.21


(k J mol -1 ) and ΔS(J mol -1 K -1 )for the corrosion of the cured positive 




Cured 

Positive 

5 

298 

308 stirred 92.63 -33.19 92.53 

(86) 

93.02 -35.51 92.90 

318 92.63 -31.26 92.54 

298 

93.60 -79.24 93.33 

308 un-stirred 93.21 -78.37 92.96 

318 92.63 -77.31 92.39 


(k J mol -1 ) and ΔS(J mol -1 K -1 )for the corrosion of the uncured 

negative working electrode in (0.56M) oxygenated H2SO4 solution in 

the absence of additives. 


Uncured 

Negative 

6 

298 

94.95 -80.59 94.68 

308 Stirred 94.56 -79.72 94.31 

318 93.99 -78.66 93.74 

298 

95.14 -86.53 94.85 

308 un-stirred 95.14 -86.24 94.86 

318 94.56 -85.37 94.30


(k J mol -1 ) and ΔS(J mol -1 K -1 )for the corrosion of the cured negative 




cured 

negative 

7 

298 

308 stirred 90.90 -87.94 90.61 

(87) 

90.90 -88.04 90.60 

318 90.70 -87.65 90.43 

298 

91.28 -85.53 91.00 

308 un-stirred 90.90 -84.95 90.62 

318 90.90 -84.76 90.63

3.6- Kinetics of Corrosion 

The rate(r) of the corrosion of the working electrode material 

increased with increasing temperature from 298 to 318 K and the behaviour 

may be described by Arrhenius equation as (93) : 

r= A exp(-E/RT) ----(3.14) 

where A and Ea are the Pre-exponential factor and the energy of activation 

respectively. The value of (r) at any temperature (T) was taken to be 

proportional to the corrosion current density (ic). The values of Ea were 

derived from the slopes of the log(ic) (85) versus 1/T plots of Fig.(3.30), 

while those of A were obtained from intercepts of the such plots at 1/T = 

zero; values of A, were expressed in term of A cm -2 , and have then been 

converted into molecules per cm -2 per second (94) . 

Table (3.22) show the resulting values of Ea and A for the corrosion of 

the working electrode material. 

The activation energy values obtained from working electrodes, in 

stirred oxygenated 0.56 M H2SO4 Solution as shown in table (3.22) may be 

arranged in a sequence as: 

2 > 3 > 5 > 1 > 6 > 7 > 4 

The pre-exponential values may also be arranged as in the sequence: 

2 > 3 > 1 > 5 > 6 > 7 > 4 

The sequence of the activation energies and pre-exponential values in 

the un-stirred oxygenated 0.56 M H2SO4 solution was as: 

3 > 1 > 2 > 7 > 4 > 5 > 6 

In stirred oxygenated 0.56 M H2SO4 solution, the highest value of the 

activation energy and of the pre-exponential was found with the grid lead 

electrode, while the lowest value of Ea and A was with obtained the 

uncured positive electrode. In un-stirred oxygenated 0.56 M H2SO4 

solution the highest value of Ea and A was with the pure lead electrode, 

(88)

while the lowest value of Ea and of A was with uncured negative electrode. 

Thus, the corrosion reaction proceeded on special surface sites, which are 

associated with different energies of activation (Ea). When the corrosion 

occurs on sites with low values of Ea, then log A is expected to be also low. 

On the other hand, when the activation energy of the surface site was high, 

the corresponding value of A was also high. 

Two mechanism have been proposed for the corrosion of lead grids, 

the first is based on the release of divalent lead ions (pb 2+ ) through a porous 

lead dioxide layer (50) and the second assumes the growth of a relatively 

impervious lead dioxide layer through ionic diffusion (95)(96) . Figs. (3.31– 

3.37) show the influence of temperature on corrosion rates which are 

expressed as corrosion current densities. 

(89)

(90)

Table (3-22):Values of activation Energies(Ea/k J mol -1 ) , pre-exponential 

factors(A/molecules cm -2 s -1 ) and Entropy of activation(DS ≠ /J mol -1 K -1 ) 

for the corrosion working electrodes in (0.56M)oxygenated H2SO4 

solution in the absence of additives. 

Electrode medium log A A Ea ΔS ≠ 

lead alloy 

1 

grid lead 

2 

pure lead 

3 

uncured 

positive 

4 

cured 

positive 

5 

uncured 

negative 

6 

cured 

negative 

7 

stirred 9.47 2.96 X 10 +9 

un-stirred 19.57 3.71 X 10 +19 

stirred 13.97 9.34 X 10 +13 

un-stirred 15.73 5.41 X 10 +15 

stirred 13.72 5.20 X 10 +13 

un-stirred 20.9 7.92 X 10 +20 

stirred 3.77 5.91 X 10 +3 

un-stirred 5.8 6.38 X 10 +5 

stirred 9.29 1.82 X 10 +9 

un-stirred 4.52 3.30 X 10 +4 

stirred 6.4 2.52 X 10 +6 

un-stirred 4.34 2.20 X 10 +4 

stirred 3.98 9.54 X 10 +3 

un-stirred 12.4 2.54 X 10 +12 

(91) 

14.64 -64.71 

38.09 129.55 

25.72 22.39 

28.56 56.14 

25.24 17.52 

41.95 154.99 

5.26 -172.79 

10.41 -133.88 

18.87 -67.77 

6.74 -158.48 

11.84 -122.45 

6.08 -161.88 

6.08 -168.80 

26.30 -7.58

(92)

(93)

(94)

(95)

4.1- Results of the Polarization Curves: 

Four types of working electrodes have been used in the research and 

these involved: 

1, cured positive electrode, 

2, cured negative electrode, 

3, lead alloy electrode, and , 

4, grid lead electrode. 

Four different additives have been added separately into the 0.56M 

sulphuric acid solution and these were: 

1, H3PO4 (11g dm -3 ), 

2, H3PO4 (11g dm -3 ) + FeSO4 (0.2g dm -3 ) mixture, 

3, NaCl (4 g dm -3 ), and , 

4, FeSO4 (0.2 g dm -3 ). 

Addition of the additive to the corrosion medium caused numerous 

alterations in the polarization behaviours of the working electrodes. 

These involved changes which occurred in the values of ic, Ec, ip, Ep, 

ba, bc, aa, ac and Rp as compared with the corresponding values which have 

been obtained in the absence of additives. 

Tables (4.1) to (4.4) show results of the polarization curves for the 

corrosion of the four types of the working electrodes, both in the stirred and 

in the unstirred oxygenated 0.56M H2SO4 solution in the presence of 

additive. 

(96)

Table(4-1):Values of ic,Ec,ip,Ep,ba,bc,αa,αc and Rp for the polarization of 

lead alloy working electrode in 0.56M oxygenated sulphuric acid 

solution in the presence of additives .Symbols were defined in Tables(3-1 

to 3-14). 

additive T/K Medium ic/10 -5 -Ec ip/10 -4 Ep ba αa -bc αc Rp 

H3PO4 

(11g 

dm -3 ) 

H3PO4 

(11g 

dm -3 ) 

+ 

FeSO4 

(o.2g 

dm -3 ) 

NaCl 

(4g dm - 

3 ) 

FeSO4 

(o.2g 

dm -3 ) 

298 4 0.520 0.8 0.840 0.12 0.50 0.27 0.22 886.77 

308 

Unstirred 

6.2 0.515 0.98 0.810 0.12 0.49 0.23 0.27 560.23 

318 7.4 0.513 1.5 0.800 0.17 0.36 0.14 0.47 447.03 

298 8.5 0.519 1.3 0.790 0.07 0.81 0.24 0.25 286.39 

308 Stirred 9 0.515 1.4 0.780 0.08 0.77 0.33 0.19 309.38 

318 1.3 0.515 1.85 0.750 0.10 0.63 0.43 0.15 269.65 

298 4.6 0.518 1 0.690 0.11 0.56 0.13 0.46 549.60 

308 

Unstirred 

6.4 0.517 2.1 0.690 0.13 0.46 0.14 0.45 452.86 

318 8.6 0.515 2.3 0.670 0.15 0.43 0.17 0.37 398.39 

298 9 0.517 2.7 0.700 0.04 1.39 0.17 0.35 164.45 

308 Stirred 11 0.514 3.9 0.670 0.04 1.42 0.19 0.32 138.13 

318 15 0.510 4.8 0.600 0.04 1.43 0.23 0.27 107.06 

298 6.3 0.516 3.5 0.710 0.07 0.81 0.25 0.23 390.78 

308 

Unstirred 

12 0.514 4.3 0.700 0.08 0.79 0.27 0.22 219.22 

318 15 0.513 6 0.700 0.09 0.73 0.29 0.21 193.51 

298 19 0.513 5.2 0.690 0.07 0.82 0.22 0.27 123.92 

308 Stirred 31 0.511 7.8 0.690 0.10 0.62 0.23 0.26 95.13 

318 33 0.511 8.3 0.670 0.31 0.20 0.27 0.23 191.57 

298 5 0.517 2.5 0.640 0.05 1.30 0.15 0.39 304.38 

308 

unstirred 

5.3 0.517 3 0.630 0.05 1.29 0.16 0.38 298.44 

318 6.8 0.515 5 0.620 0.05 1.22 0.17 0.37 253.27 

298 12.5 0.515 3.6 0.630 0.07 0.88 0.16 0.37 164.69 

308 stirred 13 0.513 4 0.630 0.09 0.66 0.18 0.34 203.11 

318 20 0.511 5.3 0.630 0.11 0.57 0.26 0.24 168.45 

(97)


lead grid working electrode in 0.56M oxygenated sulphuric acid solution 

in the presence of additives.Symbols were defined in Tables(3-1 to 3-14). 

Additiv 

e 

H3PO4 

(11g 

dm -3 ) 

H3PO4 

(11g 

dm -3 ) 

+ 

FeSO4 

(o.2g 

dm -3 ) 

NaCl 

(4g dm - 

3 ) 

FeSO4 

(o.2g 

dm -3 ) 

T/K medium ic/10 -5 

-Ec ip/10 -4 Ep ba αa -bc αc Rp 

298 3 0.529 7 0.980 0.08 0.72 0.25 0.24 894.56 

308 

unstirred 

5 0.527 8 0.860 0.15 0.41 0.31 0.20 878.74 

318 8.8 0.526 8.5 0.840 0.16 0.40 0.52 0.12 592.40 

298 4.2 0.527 7.2 0.900 0.18 0.33 0.22 0.27 1014.59 

308 stirred 7 0.525 7.9 0.850 0.23 0.26 0.28 0.22 793.62 

318 9.6 0.524 9 0.840 0.35 0.18 0.29 0.22 710.72 

298 4.6 0.528 8.9 1.030 0.04 1.43 0.37 0.16 350.19 

308 

unstirred 

6.2 0.527 9.3 0.880 0.05 1.28 0.22 0.27 275.61 

318 9.1 0.525 9.8 0.860 0.10 0.63 0.21 0.31 322.63 

298 10 0.526 8 0.930 0.04 1.53 0.57 0.10 156.78 

308 stirred 12 0.525 8.1 0.870 0.04 1.42 0.59 0.10 115.86 

318 16 0.524 10 0.840 0.04 1.51 0.93 0.07 108.72 

298 12 0.522 33 0.760 0.03 1.89 0.16 0.37 183.07 

308 

unstirred 

7.5 0.521 43 0.760 0.04 1.55 0.17 0.36 185.20 

318 9 0.520 57 0.750 0.04 1.53 0.20 0.32 164.01 

298 12 0.521 55 0.740 0.12 0.51 0.20 0.30 263.65 

308 stirred 15 0.520 8 0.730 0.15 0.40 0.25 0.25 275.31 

318 22 0.519 9.6 0.720 0.18 0.35 0.45 0.14 251.59 

298 5 0.525 1.2 0.730 0.35 0.17 0.22 0.27 1179.48 

308 

unstirred 

6.5 0.524 2 0.700 0.41 0.15 0.24 0.25 1012.93 

318 8.2 0.520 2.5 0.710 0.51 0.12 0.37 0.17 1128.33 

298 11 0.523 25 0.720 0.09 0.63 0.25 0.24 266.46 

308 stirred 15 0.523 27.5 0.710 0.10 0.61 0.28 0.22 212.73 

318 16.5 0.522 33 0.610 0.12 0.52 0.31 0.20 229.78 

(98)


cured positive lead alloy working electrode in 0.56M oxygenated 

sulphuric acid solution in the presence of additives .Symbols were 

defined in Tables (3-1 to 3-14). 

Additiv 

e 

H3PO4 

(11g 

dm -3 ) 

H3PO4 

(11g 

dm -3 ) 

+ 

FeSO4 

(o.2g 

dm -3 ) 

NaCl 

(4g dm - 

3 ) 

FeSO4 

(o.2g 

dm -3 ) 

T/K medium ic/10 -5 


298 5 0.539 1 0.830 0.05 1.13 0.12 0.50 3.15 

308 

unstirred 

5.5 0.539 1 0.820 0.05 1.23 0.14 0.45 2.89 

318 6.3 0.538 2 0.810 0.06 1.05 0.22 0.29 3.25 

298 9 0.537 1.2 0.810 0.05 1.21 0.15 0.39 1.79 

308 stirred 10 0.537 1.3 0.790 0.06 1.11 0.19 0.32 1.86 

318 13 0.536 1.7 0.760 0.08 0.80 0.22 0.28 1.95 

298 5.6 0.527 1.4 0.840 0.09 0.67 0.11 0.56 3.72 

308 

unstirred 

6 0.526 1.52 0.840 0.10 0.61 0.11 0.57 3.75 

318 6.7 0.525 1.9 0.830 0.17 0.37 0.11 0.56 4.41 

298 9 0.521 1.12 0.790 0.05 1.22 0.11 0.54 1.62 

308 stirred 15 0.520 1.25 0.770 0.07 0.93 0.13 0.47 1.27 

318 17.5 0.520 1.65 0.730 0.09 0.69 0.14 0.47 1.35 

298 10.6 0.485 3.4 0.730 0.04 1.42 0.15 0.39 1.34 

308 

unstirred 

18 0.484 3.4 0.700 0.05 1.13 0.16 0.37 0.98 

318 20 0.483 3.9 0.710 0.06 1.03 0.18 0.34 1.00 

298 13 0.483 3.6 0.740 0.04 1.40 0.15 0.38 1.11 

308 stirred 21 0.483 6.3 0.730 0.05 1.29 0.18 0.35 0.77 

318 24 0.481 9 0.720 0.05 1.21 0.19 0.33 0.74 

298 6.3 0.518 3 0.740 0.05 1.26 0.13 0.45 2.37 

308 

unstirred 

6.9 0.518 3.3 0.740 0.05 1.23 0.18 0.33 2.46 

318 8 0.516 5 0.720 0.05 1.17 0.28 0.22 2.46 

298 10 0.505 3.2 0.720 0.04 1.55 0.12 0.51 1.25 

308 stirred 12 0.503 3.4 0.710 0.04 1.46 0.12 0.50 1.13 

318 15 0.500 3.55 0.710 0.05 1.25 0.17 0.37 1.12 

(99)


cured negative lead alloy working electrode in 0.56M oxygenated 

sulphuric acid solution in the presence of additives .Symbols were 

defined in Tables(3-1 to 3-14). 

Additive T/K medium ic/10 -5 

H3PO4 

(11g dm -3 ) 

H3PO4 

(11g dm -3 ) 

+ 

FeSO4 

(o.2g dm -3 ) 

NaCl 

(4g dm -3 ) 

FeSO4 

(o.2g dm -3 ) 


298 0.82 0.537 2.7 0.820 0.08 0.73 0.14 0.42 2.73 

308 

unstirred 

0.93 0.536 2.9 0.810 0.09 0.64 0.17 0.37 2.82 

318 0.95 0.535 3.2 0.810 0.10 0.62 0.18 0.35 2.97 

298 0.825 0.533 3.1 0.790 0.23 0.26 0.15 0.39 4.83 

308 stirred 0.925 0.530 3.1 0.780 0.27 0.22 0.17 0.37 4.84 

318 0.98 0.530 4.25 0.780 0.33 0.19 0.18 0.35 5.23 

298 0.95 0.525 3.4 0.820 0.05 1.19 0.15 0.40 1.71 

308 

unstirred 

1.15 0.523 3.5 0.800 0.06 0.98 0.19 0.32 1.78 

318 1.2 0.523 4.5 0.790 0.07 0.97 0.38 0.17 2.01 

298 1.1 0.521 3.3 0.800 0.08 0.78 0.09 0.63 1.65 

308 stirred 1.15 0.520 3.8 0.790 0.08 0.76 0.16 0.39 2.01 

318 1.2 0.520 3.9 0.790 0.10 0.61 0.19 0.33 2.42 

298 2 0.473 6.9 0.700 0.04 1.38 0.13 0.46 0.70 

308 

unstirred 

2.4 0.472 7 0.690 0.04 1.37 0.14 0.43 0.61 

318 3.3 0.471 8.9 0.690 0.05 1.38 0.16 0.41 0.46 

298 1.5 0.472 6.5 0.690 0.05 1.27 0.11 0.54 0.95 

308 stirred 1.9 0.470 6.9 0.690 0.06 1.04 0.12 0.53 0.89 

318 2 0.470 9.5 0.670 0.06 1.00 0.13 0.49 0.92 

298 1 0.516 3.1 0.740 0.05 1.25 0.12 0.49 1.48 

308 

unstirred 

1 0.514 3.4 0.730 0.05 1.16 0.17 0.36 1.74 

318 1.2 0.513 3.5 0.730 0.06 1.10 0.19 0.33 1.60 

298 1.2 0.513 5 0.740 0.04 1.47 0.14 0.44 1.12 

308 stirred 1.7 0.513 5.25 0.720 0.04 1.58 0.21 0.29 0.83 

318 2.25 0.511 5.7 0.710 0.05 1.30 0.52 0.12 0.85 

(100)

4.1.1- Corrosion Potentials (Ec): 

Tables (4.1) to (4.4) show values of the Ec which have been obtained 

from the polarization curves in the presence of the additives which may be 

summarized as in the following: 

1. Values of Ec for the different working electrodes shifted to more 

negative values in the presence of additive as compared with the 

corresponding values in the absence of additive indicating an increasing 

tendency of the electrode for corrosion. 

2. Values of Ec in stirred oxygenated 0.56 M sulphuric acid solution 

was less negative than the values in the un-stirred oxygenated 0.56M 

H2SO4 solution. 

3. Values of Ec for the corrosion of the four working electrodes 

increased at constant H2SO4 concentration with increasing temperature. 

The results of Figs.(4.1) to (4.8) show the effect of additives on the 

values of the corrosion potentials of the electrode materials in stirred 

oxygenated 0.56M sulphuric acid solution which may be arranged from 

more negative to less negative in a sequence as: 

was as: 

2 > 3 > 5 > 4 > 1 

The sequence in un-stirred oxygenated acid solution on similar basis 

2 > 3 > 5 > 1 > 4 

Thus, in both stirred and un-stirred oxygenated 0.56 M sulphuric acid 

solution, the addition of H3PO4 had a greater influence on shifing the 

corrosion potential to a more negative value. The addition of sodium 

chloride shifted the Ec to least negative value in un-stirred acid solution. In 

stirred oxygenated acid solution, the values of Ec were less negative in the 

absence of additives as compared with the presence of the additives. 

(101)

The grid lead showed the greatest tendency for corrosion, while the 

cured negative electrode material had the least tendency for corrosion. 

Curing of the positive electrode or of the negative electrode reduced the 

tendency for corrosion. The additives reduced the corrosion tendency as 

compared with the tendency in the absence of additives. 

(102)

(103)

(104)

(105)

(106)

4.1.2- Corrosion Current Densities (ic) 

The corrosion current density (ic) represents the rate of corrosion 

under equilibrium condition. 

Tables (4.1) to (4.4) show values of ic, and hence of corrosion rates, 

of the electrode materials in the presence of additives in the both unstirred 

and stirred oxygenated acid solutions. In general, values of ic were higher 

in stirred solution than in unstirred solution. 

The behaviours of the four electrode materials in the presence of the 

various additives may be compared with each other with the aid of the 

Figs.(4.9) to (4.16). The corrosion rates of the materials in stirred and un- 

stirred oxygenated acid solution may be presented in the following 

sequence: 

1 > 4 > 5 > 3 > 2 

Thus, the highest corrosion inhibition was caused by the addition of 

phosphoric acid (11g dm -3 ) in both stirred and un-stired 0.56 M H2SO4 

solution with respect to all the electrode materials. The less corrosion 

inhibition was caused by ferrous sulphate (0.2g dm -3 ) and sodium chloride 

(4g dm -3 ) in stirred and un-stirred oxygenated 0.56 M H2SO4 solution as 

compared with acid solution without additives. 

The largest coorosion rate in stirred oxygenated solution may be 

accounted for on the bases of the greater reactivity of the material surface 

towards oxygen. 

(107)

(108)

(109)

(110)

(111)

4.1.3- Passive Potentials (Ep) 

The passive potential (Ep) is the potential at which a stable passive 

layer is formed on the electrode surface. The greater value of Ep, the more 

noble is the passive potential and hence a greater work should be required 

to attain such state. When the value of Ep is low, a relatively smaller 

electrical work is needed to lay down a compact passive layer on the 

electrode surface. When two values of Ep are compared for two different 

electrodes or under two different experimental conditions, the lowest value 

of Ep then corresponds to a smaller work that is required to achieve 

passivity as compared with the larger value of Ep. The passive lay is 

expected in all cases to be an oxide or sulphate layer on the electrode 

surface. 

Values of passive potentials (Ep) for the corrosion of the four electrode 

materials decreased with increasing temperature and the values of (Ep) in 

un-stirred oxygenated acid solution were generally greater than the values 

in stirred oxygenated acid solution in the presence of the additives as 

shown in tables(4.1) to (4.4). 

The sequence of Ep values for the corrosion of lead alloy electrode in 

un-stirred oxygenated acid solution may be arranged as in the following : 

2 > 1 > 3 > 5 > 4 

the sequence in stirred oxygenated acid solution was: 

1 > 2 > 3 > 5 > 4 

For grid lead the sequence of Ep values in un-stirred oxygenated acid 

solution was: 

2 > 3 > 1 > 5 > 4 

and in stirred oxygenated acid solution the sequence was: 

2 > 1 > 3 > 5 > 4 

(112)

For cured positive and cured negative electrodes the sequence of Ep values 

in un-stirred acid solution was: 

2 > 3 > 1 > 5 > 4 

In the stirred oxygenated acid solution the sequence of Ep values for 

cured positive and cured negative electrodes was: 

3 > 2 > 1 > 5 > 4 

(113)

4.1.4- Passive Current Densities (ip) 

The passive current density (ip) represents the corrosion rate of the 

electrode surface in the passive state. The lower the value of ip the more 

stable is the passive layer on the electrode surface and hence the lower is 

the corrosion rate when the electrode surface attains such state. On the 

other hand, the greater the value of ip, the less stable is the passive layer, 

and hence the higher is the corrosion rate of the electrode when it attains 

such state. When two values of ip are compared, the greater ip value 

corresponds to less stable passive state and hence to larger corrosion rate as 

compared with the lower value of ip. The ip value is the corrosion current 

density of the electrode surface subsequent to its coating with the surface 

passive (oxide or sulphate) layer. 

Tables (4.1) to (4.4) show values of the passive current densities (ip) 

of the four working electrode materials in the stirred and un-stirred 

oxygenated 0.56 M H2SO4 solution in the presence of additives. 

Values of ip for all electrode materials increased with increasing 

temperature and the values of ip in stirred oxygenated acid solution were 

greater than the corresponding values in un-stirred oxygenated acid 

solution. 

Tables (4.1) to (4.4) indicate the effect of the various additives on the 

values of ip for the electrodes as compared with ip values in the absence of 

additives. The effect of additive for lead alloy in stirred and un-stirred 

oxygenated acid solution may be arranged as: 

4 > 5 > 3 > 2 > 1 

For grid lead, the sequence in stirred oxygenated acid solution was: 

1 > 4 > 5 > 3 > 2 

In un-stirred oxygenated acid solution the sequence was: 

4 > 5 > 3 > 1 > 2 

(114)

The sequence for the cured positive electrode and cured negative electrode 

in the both stirred and un-stirred oxygenated acid solution was as: 

1 > 4> 5> 3 > 2 

The greatest effect was obtained in the presence of NaCl, while the 

smallest effect was observed in the presence of H3PO4. 

The passive current density (ip) decreased generally on moving from 

the left to right in the sequences. The decrease of (ip) should be connected 

with the increasing stability of the oxide film, while the subsequent 

increase in ip implies a decrease in the stability of the oxide or sulphate film 

which is formed on the electrode surface. 

(115)

4.2- Tafel Slopes and Transfer Coefficients 

Tables (4.1) to (4.4) show the influence of temperature (T) and 

concentration (C) of the additives on the cathodic (bc) and anodic (ba) Tafel 

slopes which have been obtained from the polarization curves of the 

working electrodes in stirred and un-stirred oxygenated 0.56M H2SO4 

solution over the temperature range 298-318K. 

Values of the transfer coefficients for the cathodic (ac) and anodic 

(aa) processes have been calculated from the corresponding cathodic (bc) 

and anodic (ba)Tafel slopes using the relationships (97) : 

c 

2. 

303RT 

= 

b F 

a ----- (3.1) 

a 

c 

2. 

303RT 

= 

b F 

a ----- (3.2) 

where R is the gas constant and F the Faraday constant. 

a 

A cathodic Tafel slope of -0.120V (or of ac =0.5) may be diagnostic 

of a discharge–chemical desorption mechanism for hydrogen evolution 

reaction of the cathode in which the proton discharge is the rate- 

determining step. If chemical desorption is the rate- determining step, the 

rate will then be independent of the overpotential since no charge transfer 

occurs in such step and the rate becomes directly proportional to the 

concentration or the coverage (q) of the adsorbed hydrogen atoms, and 

may occur at coverages ranging from very small values to almost full 

surface layer formation (88) . The expected Tafel slope in such step would 

then be –0.03V decade -1 and ac=2.0. 

When electrochemical desorption becomes the rate–determining step 

for the hydrogen evolution reaction on the cathode, the expected value of 

bc is –0.05 decade -1 and ac=1.5. 

(116)

Values of the anodic Tafel slopes (ba) are shown in the tables of 

chapter III (Tables (3.1-3.14)) and IV(Tables(4.1-4.4)) to be close to 0.120 

decade -1 in some cases, and those of the corresponding anodic transfer 

coefficients (aa) were also close to 0.5, indicating that the metal dissolution 

reaction to be the rate- determining step for the dissolution reactions taking 

place at the anode. 

The results of the tables indicate that the variation of the Tafel slopes 

and of the corresponding transfer coefficients could be interpreted in terms 

of the variation of the rate-determining step from charge transfer process to 

either chemical-desorption or to electrochemical desorption. 

The variation of the anodic transfer coefficients (aa) may be attributed 

to the variation of the rate-determining step in the metal dissolution 

reaction. A change in mechanism as well as in the rate- determining step, 

cannot be ignored throughout the anodic processes (98) . 

(117)

4.3- Polarization Resistance 

Another approach to the problem of electrochemical corrosion rate 

measurement is to apply only a small potential difference to the specimen 

and then measure the current density. The potential –current density plot is 

approximately linear in the region within –10mV of the corrosion potential. 

The slope of this plot in terms of potential divided by current density has 

the units of resistance area and is often called the polarization resistance 

(Rp). The polarization resistance (Rp) is related to the corrosion current 

density by the relationship: (99) 

Rp = 

babc 

2 . 303( 

b + b ) i 

a 

c 

c 

(118) 

---- (3.10) 

Where ic is the corrosion current density, and ba and bc are the magnitudes 

of the Tafel slopes of the anodic and cathodic Tafel lines respectively. 

The measurement of polarization resistance has very similar 

requirements to the measurement of full polarization curves and it is 

particularly useful as a method to rapidly identify corrosion upsets and 

initiates remedial action. (100) 

The results of Tables (4.1-4.4) indicate the following: 

1. Values of the polarization resistance were higher in un-stirred 

oxygenated acid solution than in stirred oxygenated solution in all cases 

and this may be accounted for on the basis of the smaller reactivity of 

the material surface towards oxygen. 

2. For the four working electrodes, the values of the polarization 

resistance in the presence of additives were generally greater than in the 

absence of additives in the both media, except in certain cases, where 

the reverse was true, and such cases were: 

a. for lead alloy in the presence of NaCl in stirred acid solution, 

b. for cured negative electrode in the presence of NaCl.

3. The greatest values of the polarization resistance which were observed 

for the electrodes in some cases were: 

a. for lead alloy and for cured negative electrode in the presence of 

H3PO4, 

b. for grid lead and cured positive electrode in un-stirred acid solution 

in the presence of H3PO4, 

c. for grid lead in stirred acid solution in the presence FeSO4, 

d. for cured positive electrode in stirred acid solution in the presence of 

(H3PO4 + FeSO4 ) mixture. 

4. The smallest values of the polarization resistance were observed in the 

following cases: 

a. for cured positive and cured negative electrodes in the presence of 

NaCl, 

b. for grid lead in stirred acid solution in the presence of NaCl, 

c. for lead alloy in the presence of FeSO4, 

d. for grid lead in un-stirred acid solution in the presence (H3PO4 + 

FeSO4) mixture. 

(119)

4.4 – Effect of Additives 

4.4.1- Phosphoric Acid 

Several attempts have been made to improve the corrosion resistance 

of lead and lead-antimony alloy electrodes. Lead forms an insoluble 

phosphate that provides protection in phosphoric acid (101) . 

Boctor (102) stated that the addition of few grams per liter of 

phosphoric acid in relatively higher concentration of sulphuric acid in the 

storage batteries, is useful to inhibit corrosion specially under high 

temperature conditions. 

Bullock and McClelland (103) have shown that phosphoric acid 

decrease the rate of the self-discharge reaction of the positive electrode: 

PbO2 + H2SO4 fi PbSO4 + H2O + ½ O2 ------ (4.1) 

in sealed lead-acid cells with pure lead grids. Visscher (104) confirmed that 

adding small quantities of phosphoric acid to approximately 5M H2SO4 

modifies the kinetics of the PbO2/ PbSO4 couple reactions. 

Bullock (105) studied the effect of H3PO4 on the constant potential 

corrosion of pure lead positive grid in the lead acid batter and found that 

the PbO2 film formed in the presence of phosphoric acid requires longer 

time to self-discharge to PbSO4 than the PbO2 film formed in pure 

electrolyte. 

Phosphoric acid reduces corrosion rate, it is apparent that the greatest 

effect is in going from zero to 0.2% H3PO4. Further increase in H3PO4 

concentration decreases the rate only slightly. 

Thus, it may be concluded that (105) : 

1- Phosphorate modifies the morphology of PbO2 formed by grid 

corrosion. 

2- Phosphate is incorporated in the PbO2 structure during corrosion 

process. 

3- These effects occur on pure lead, antimonial and non-antimonial lead 

alloys as well. 

(120)

4.4.2- Mixture of H3PO4 and FeSO4 

The addition of (11g) of phosphoric acid (H3PO4) to one litre of 

sulphuric acid electrolyte results in a solution in which the H3PO4 is 

subjected to a change during discharging and charging processes of the 

lead-acid battery. It is established that H3PO4 undergoes some absorption 

by the positive plates (PbO2) through the charging process of the battery 

and ah part of the absorbed H3PO4 will return and transfer to the 

electrolyte. 

It was proved (106) that the addition of phosphoric acid to the 

electrolyte causes formation of Pb(IV) ions on charging of the positive 

plates and he particles of Pb(IV) may precipitate as a jelly like mass of 

white colour in the bottom of the electrolyte. The particles may oxidize 

some organic materials, which are present in the battery structure resulting 

in the formation of Pb at he negative plates of the battery. 

As a result it will cause premature failure of the negative plates. The 

formation of Pb(IV) is therefore undesirable whether as soluble ions or 

jellylike particles and in order to prevent this an amount of Fe +2 ions 

(0.2 g) is usually added to the electrolyte to reduce the corrosion of 

Pb(IV) particles to Pb(II). 

As a conclusion, the H3PO4 decreases the rate of corrosion of the 

positive plates and hence the rate of dropping of the active mass of the 

plates. The presence of Fe 2+ with H3PO4 in the acid solution reduces the 

conversion of Pb (IV) to Pb(II). (107) 

(121)

4.4.3- Ferrous Sulphate (FeSO4) 

Adding an amount of Fe +2 ions (0.2g dm -3 ) as FeSO4 to the electrolyte 

is necessary to control the extent of the formation of Pb(IV) and it is 

confirmed that :- (108) 

1- The Fe +2 ions should be added to the electrolyte as a soluble ferrous 

sulphate (FeSO4). 

2- Adding 0.05 g of FeSO4 to the electrolyte has no effect on the 

capacity of the battery and on the dropping of active mass of the plates. 

3- The formation of Pb(IV) particles may be presented only when the 

concentration of FeSO4 in the acid solution becomes 0.2 g for each litre 

of the sulphuric acid electrolyte. 

At this concentration of FeSO4, the capacity of the battery may 

decrease by 5% and the rate of dropping of the active mass of the positive 

plates decreases by about 80%. 

4.4.4- Sodium Chloride (NaCl): 

Adding (4g) of NaCl to one litre of the sulphuric acid electrolyte may 

cause corrosion of lead by the formation of PbCl2 film (48) . 

The film of poorly soluble PbCl2 is formed via the process: 

Pb + 2Cl - fi PbCl2 + 2e ----- (4.2) 

This reaction may be compared with the formation of the sulphate 

system as represented by the reaction: 

Pb + SO4 2- fi PbSO4 + 2e ----- (4.3) 

The analogy ends when it is realized firstly that the chloride of lead is 

some 300 times more soluble in water or in an aqueous media than lead 

sulphate, and secondly, in practice, the importance of lead in sulphate 

media focuses on solutions high in sulphate concentration (strong sulphuric 

acid) which are relatively quiescent. 

(122)

4.5- Protection Efficiency 

The corrosion current densities in the presence and absence of 

additives in the corrosion medium have been used to determine the 

protection efficiency (P%) using the relation (109,110,94) 

i 2 

P%= 100 [ 1- ] ----- (4.4) 

i1 

where i1 and i2 are the corrosion current densities in the absence and 

presence additive in the corrosion medium respectively. 

A positive value of P% indicates inhibition of corrosion by the added 

additive while a negative value of P% implies corrosion stimulation or 

corrosion acceleration. 

The results of Tables (4.5-4.8) and of Figs.(4.17-4.28) reveal the 

following: 

1. Values of the protection efficiency (P%) were higher in stirred 

oxygenated acid solution than in unstirred oxygenated solution in the 

all cases except for cured positive electrode where the reverse case was 

holding. Stirring in the former cases may cause a closer contact 

between the additive and the electrode surface resulting in a higher 

percentage of protection efficiency. Stirring may also result in the 

formation of a more compact passive layer by the dissolved oxygen. 

For cured positive electrode, the values of P% were higher in unstirred 

oxygenated solution than in the stirred solution in the presence of the 

additives 1, 2 and 4. Such behaviour may be attributed to the different 

nature of this electrode which was mainly in the form of PbO2 and not as 

metallic lead. 

2. The order of the variation of P% values in most cases lied in the 

sequence : 

1 > 2 > 4 > 3 

(123)

irrespective of the type of the additive which was present in the oxygenated 

acid solution, and also irrespective of the presence or the absence of 

stirring. 

3. The lowest P% values were obtained in such cases as: 

a- for grid lead, lead alloy and cured negative electrode in unstirred 

oxygenated acid solution containing dissolved NaCl, 

b- For grid lead in unstirred oxygenated acid solution containing 

dissolved FeSO4, 

c- NaCl caused the lowest protection efficiency than the other three 

additives in the both stirred and unstirred oxygenated solution with 

respect to all the four types of electrode materials. 

4. Stirring of the acid solution had largest effect in enhancing the value 

of protection effect in enhancing the value of protection efficiency P% 

in the case of grid lead and lead alloy electrodes in the presence of NaCl 

as additive. 

5. H3PO4 was most effective in raising P% values: 

(a) with grid lead, lead alloy and cured negative electrode in the stirred 

oxygenated solution. 

(b) with cured positive electrode in unstirred oxygenated acid solution. 

6. The (H3PO4 + FeSO4) mixture was less effective than H3PO4 alone in 

raising the value of P% and such effect was more pronounced in the 

case of lead alloy in the stirred oxygenated solution. 

7. The temperature dependencies of P% values were as follows:- 

a. for lead alloy, were lowest in the presence of NaCl. The temperature 

dependence remained almost constant in stirred oxygenated solution; it 

may be specified as almost independent of temperature in such cases. 

With the other three cases, the temperature dependence in unstirred 

oxygenated acid solution was markedly temperature dependent and the 

(124)

dependence attained maximum values at 308K. NaCl presence in certain 

cases caused corrosion acceleration. 

b. P% values with grid lead in the presence of H3PO4 in stirred 

oxygenated solution were almost independent of temperature. With the 

other additives including NaCl, values of P% increased by some 5% 

with temperature in the stirred oxygenated solution. In the unstirred 

solution, P% became highest at 298K in the presence of H3PO4 but 

decreased sharply with the rise of temperature. With (H3PO4 + FeSO4 

)mixture, P% values increased with temperature from 298 to 308K and 

then decreased with further increase in temperature. With the other 

additives, there was an increase in P% with the rise of temperature. 

c. with cured positive electrode, the variation of P% with temperature 

in the unstirred solution was almost similar to that obtained with H3PO4 

for lead alloy electrode in the stirred oxygenated solution. In the 

unstirred oxygenated solution, the variation of P% values was almost 

similar to the behaviour of lead alloy in the unstirred oxygenated 

solution. 

d. With cured negative electrodes, the variation of P% values with 

temperature had certain similarities with those for lead alloy with the 

exception of NaCl behaviour. While NaCl caused an increase in P% 

values with temperature in the unstirred oxygenated solution, it resulted, 

on the other hand, in a decrease of P% values with increasing 

temperature. 

(125)

Table(4-5):Protection efficiencies(P%) for the corrosion of the lead 

alloy in (0.56M) oxygenated H2SO4 solution in the presence of 

additives. 

(126) 

p% 

T/K medium H3PO4 (H3PO4 

(11g dm -3 )+ 

(11g dm -3 ) FeSO4(0.2g 

dm -3 )) 

NaCl FeSO4 

(4g dm -3 ) (0.2g dm -3 ) 

298 38.46 29.23 3.08 23.08 

308 un-stirred 55.71 54.29 14.29 62.14 

318 56.47 49.41 11.76 60.00 

298 69.09 67.27 30.91 54.55 

308 stirred 68.97 62.07 -8.62 55.17 

318 67.50 62.50 17.50 50.00 

Table(4-6):Protection efficiencies(P%) for the corrosion of the grid 

lead in (0.56M) oxygenated H2SO4 solution in the presence of 

additives. 

p% 


(11g dm -3 )+ 

(11g dm -3 ) FeSO4(0.2g 

dm -3 )) 

NaCl FeSO4 

(4g dm -3 ) (0.2g dm -3 ) 

298 52.38 26.98 1.59 20.63 

308 un-stirred 47.37 34.74 21.05 31.58 

318 32.31 30.00 30.77 36.92 

298 83.85 61.54 53.85 57.69 

308 stirred 80.00 65.71 57.14 61.43 

318 80.80 68.00 56.00 67.00

Table(4-7):Protection efficiencies(P%) for the corrosion of the cured 

positive in (0.56M) oxygenated H2SO4 solution in the presence of 

additives. 

(127) 

p% 


(11g dm -3 )+ 

(11g dm -3 ) FeSO4(0.2g 

dm -3 )) 

NaCl FeSO4 

(4g dm -3 ) (0.2g dm -3 ) 

298 68.75 65.00 33.75 60.63 

308 un-stirred 67.65 64.71 -5.88 59.41 

318 66.84 64.74 -5.26 57.89 

298 60.87 60.87 43.48 56.52 

308 stirred 71.43 57.14 40.00 65.71 

318 64.86 52.70 35.14 59.46 

Table(4-8):Protection efficiencies(P%) for the corrosion of the cured 

negative in (0.56M) oxygenated H2SO4 solution in the presence of 

additives. 


(11g dm -3 )+ 

(11g dm -3 ) FeSO4(0.2g 

dm -3 )) 

p% 

NaCl FeSO4 

(4g dm -3 ) (0.2g dm -3 ) 

298 50.30 42.42 9.09 39.39 

308 un-stirred 69.00 61.67 36.67 66.67 

318 70.31 62.50 37.50 62.50 

298 72.50 63.33 33.33 60.00 

308 stirred 71.97 65.15 27.27 48.48 

318 72.00 65.71 5.71 35.71

(128)

(129)

(130)

(131)

(132)

(133)

4.6- Thermodynamics of Corrosion 

Thermodynamic laws tell us that there is a strong tendency for high 

energy states of metals to transform into low energy states. It is this 

tendency of metals to recombine with components of the environment that 

leads to the phenomenon which is known as corrosion (111) . 

Tables (4.9) to (4.12) give values of the thermodynamic quantities 

(DG, DH and DS) for the corrosion of the working electrodes in the stirred 

and unstirred oxygenated sulphuric acid solution. Figs.(4.29-4.32) represent 

the temperature dependencies of DG in the both media. 

The results of tables (4.9-4.12) and of Figs.(4.33-4.44) indicate the 

following:- 

1- Values of DG were generally negative suggesting the existence of 

thermodynamic feasibility for the corrosion of the electrodes materials 

in oxygenated sulphuric acid solution in the absence or the presence of 

the additives in the acid solution. 

Values of DG for the different working electrodes were slightly more 

negative in the unstirred oxygenated acid solution than in the stirred 

oxygenated acid solution. The presence of additives in the oxygenated acid 

solution caused a shift to more negative DG values as compared with the 

case where no additive was present in the acid solution. 

It is also shown that the effect of shifting DG to more negative values 

may be arranged in a sequence as: 

2 > 3 > 5 > 4 

Thus, H3PO4 and its mixture with FeSO4 were the most effective in 

shifting the DG to more negative values. 

2- DH values were generally negative indicating a stronger bonding of 

the metal ions, resulting from electrode corrosion, with the species that 

are present in the corrosion medium as compared with the bonding of 

(134)

the metal atoms in the crystal lattice of the solid electrode. Values of DH 

were more negative in the presence of additives in the corrosion 

medium than when such additives were absent. 

Stirring of the oxygenated acid solution resulted in a less negative DH 

values, except in certain cases, where the reverse behaviour was true, and 

such cases were:- 

a. for lead alloy in the presence of H3PO4, 

b. for grid lead, for cured positive and cured negative electrodes in the 

presence of H3PO4 + FeSO4 mixture in the corrosion medium, and, 

c. for cured negative electrode in the presence of FeSO4. 

The most effective additives in altering the DH values in the more 

negative direction were: 

(i) FeSO4, NaCl, (FeSO4+ H3PO4) mixture, and H3PO4 with lead 

alloy, 

(ii) (FeSO4 + H3PO4) mixture, NaCl, H3PO4 and FeSO4 with grid 

lead, 

(iii) H3PO4, (H3PO4 + FeSO4) mixture, FeSO4 and NaCl with cured 

positive electrode, and , 

(iv) H3PO4, (H3PO4 + FeSO4)mixture, FeSO4 and NaCl with cured 

negative electrode. 

These results suggest stronger bonding in the presence of these 

additives of the resulting metal ions with the existing charged species 

which are present in the oxygenated acid medium as compared with the 

state of the metal atoms while they are present in the surface lattices of the 

corroding electrodes. 

3- Values of DS were generally positive due to greater negativity of DG 

values than the corresponding DH values. This suggests a smaller order 

(135)

in the solvated states of the metal ions as compared with the state of 

metal atoms in the crystal lattice of the corroding electrodes. 

Values of DS were more positive in the presence of additives than in 

their absence. The only exception to this statement was for grid lead and 

cured negative electrode in the presence of NaCl in the corrosion medium. 

Stirring of the acid solution caused a slight decrease in the values of DS 

with respect to all the working electrodes. 

The H3PO4 and its mixture with FeSO4 were the most effective 

additives in increasing the values of DS. 

(136)

Table(4-9):Values of the thermodynamics quantities -ΔG,ΔH(k J mol -1 ) 

and ΔS (J mol -1 K -1 )for the corrosion of the lead alloy working electrode 

in (0.56M) oxygenated H2SO4 solution in the presence of additives. 

Additive T/K medium -ΔG ΔH ΔS 

H3PO4 

(11g dm -3 ) 

FeSO4 

(o.2g dm -3 ) 

+ 

H3PO4 

(11g dm -3 ) 

NaCl 

(4g dm -3 ) 

FeSO4 

(o.2g dm -3 ) 

298 

308 un-stirred 99.39 -69.67 99.16 

(137) 

100.35 -71.60 100.11 

318 98.42 -67.74 98.21 

298 

100.16 -88.66 99.86 

308 stirred 99.39 -87.50 99.10 

318 99.39 -87.11 99.11 

298 

99.97 -91.36 99.66 

308 un-stirred 99.78 -90.88 99.49 

318 99.40 -90.20 99.11 

298 

99.78 -85.42 99.49 

308 stirred 99.20 -84.36 98.93 

318 98.82 -83.49 98.55 

298 

99.59 -90.95 99.28 

308 un-stirred 99.20 -90.27 98.91 

318 99.01 -89.79 98.73 

298 

99.01 -90.40 98.71 

308 stirred 98.62 -89.72 98.33 

318 98.43 -89.24 98.15 

298 

99.78 -94.03 99.47 

308 un-stirred 99.78 -93.84 99.48 

318 99.40 -93.26 99.10 

298 

99.40 -85.00 99.11 

308 stirred 98.43 -83.55 98.16 

318 98.43 -83.07 98.17


and ΔS (J mol -1 K -1 )for the corrosion of the grid lead working electrode 

in (0.56M) oxygenated H2SO4 solution in the presence of additives. 

additive T/K medium -ΔG ΔH ΔS 

H3PO4 

(11g dm -3 ) 

FeSO4 

(o.2g dm -3 ) 

+ 

H3PO4 

(11g dm -3 ) 

NaCl 

(4g dm -3 ) 

FeSO4 

(o.2g dm -3 ) 

298 

308 un-stirred 101.71 -92.78 101.41 

(138) 

102.10 -93.46 101.78 

318 101.52 -92.30 101.23 

298 

101.71 -93.07 101.40 

308 stirred 101.33 -92.39 101.03 

318 101.13 -91.91 100.84 

298 

101.90 -93.29 101.59 

308 un-stirred 101.71 -92.81 101.41 

318 101.33 -92.13 101.04 

298 

101.52 -95.77 101.20 

308 stirred 101.33 -95.38 101.02 

318 101.13 -94.99 100.83 

298 

100.75 -94.99 100.43 

308 un-stirred 100.55 -94.61 100.25 

318 100.36 -94.22 100.06 

298 

100.55 -94.80 100.23 

308 stirred 100.36 -94.42 100.05 

318 100.17 -94.03 99.87 

298 

101.33 -92.71 101.01 

308 un-stirred 101.13 -92.23 100.83 

318 100.75 -91.56 100.46 

298 

100.94 -92.33 100.63 

308 stirred 100.94 -92.04 100.64 

318 100.75 -91.56 100.46


and ΔS (J mol -1 K -1 )for the corrosion of the cured positive working 

electrode in (0.56M) oxygenated H2SO4 solution in the presence of 

additives. 


H3PO4 

(11g dm -3 ) 

FeSO4 

(o.2g dm -3 ) 

+ 

H3PO4 

(11g dm -3 ) 

NaCl 

(4g dm -3 ) 

FeSO4 

(o.2g dm -3 ) 

298 

308 un-stirred 104.03 -101.04 103.70 

(139) 

104.03 -101.14 103.69 

318 103.83 -100.75 103.52 

298 

103.64 -100.75 103.30 

308 stirred 103.64 -100.65 103.31 

318 103.45 -100.36 103.13 

298 

101.71 -95.96 101.39 

308 un-stirred 101.52 -95.57 101.21 

318 101.33 -95.19 101.03 

298 

100.55 -97.66 100.23 

308 stirred 100.36 -97.37 100.04 

318 100.36 -97.28 100.05 

298 

93.61 -87.85 93.31 

308 

un-stirred 

93.41 -87.47 93.13 

318 93.22 -87.08 92.95 

298 

93.22 -87.47 92.93 

308 stirred 93.22 -87.27 92.94 

318 92.83 -86.70 92.56 

298 

99.97 -94.22 99.66 

308 un-stirred 99.97 -94.03 99.67 

318 99.59 -93.45 99.29 

298 

97.47 -88.82 97.17 

308 stirred 97.08 -88.15 96.79 

318 96.89 -87.66 96.61


and ΔS (J mol -1 K -1 )for the corrosion of the cured negative working 

electrode in (0.56M) oxygenated H2SO4 solution in the presence of 

additives. 


H3PO4 

(11g dm -3 ) 

FeSO4 

(o.2g dm -3 ) 

+ 

H3PO4 

(11g dm -3 ) 

NaCl 

(4g dm -3 ) 

FeSO4 

(o.2g dm -3 ) 

298 

308 un-stirred 103.45 -97.50 103.13 

(140) 

103.64 -97.89 103.31 

318 103.26 -97.12 102.95 

298 

102.87 -94.26 102.55 

308 stirred 102.29 -93.39 101.99 

318 102.29 -93.10 102.00 

298 

101.33 -95.57 101.00 

308 un-stirred 100.94 -94.99 100.63 

318 100.94 -94.80 100.64 

298 

100.55 -97.66 100.23 

308 stirred 100.36 -97.37 100.04 

318 100.36 -97.28 100.05 

298 

91.29 -85.54 91.00 

308 un-stirred 91.10 -85.15 90.82 

318 90.90 -84.77 90.64 

298 

91.10 -85.34 90.81 

308 stirred 90.71 -84.77 90.43 

318 90.71 -84.57 90.44 

298 

99.59 -90.95 99.28 

308 un-stirred 99.20 -90.27 98.91 

318 99.01 -89.79 98.73 

298 

99.01 -93.26 98.70 

308 stirred 99.01 -93.06 98.71 

318 98.62 -92.49 98.33

(141)

(142)

(143)

(144)

(145)

(146)

(147)

(148)

4.7- Kinetic of Corrosion 

The rate(r) of the corrosion of lead-acid battery plates and components 

increased with increasing temperature form 298 to 318K. The behaviour 

obeyed Arrhenius type equation as: 

ic = A exp(-Ea/RT) ----- (4.5) 

where ic is the rate of corrosion in terms of corrosion current density, A and 

Ea are the pre- exponential factor and energy of activation of the corrosion 

process respectively. 

Values of Ea were derived from the slopes of the log ic versus 1/T 

linear plots as in Figs. (4.45-4.52), while those of A were obtained from the 

intercepts of the plots at 1/T = zero; values of A, expressed in term of Am -2 , 

have then been converted into molecules per m 2 per second . A was defined 

as: 

where 

K =Boltzman constant, 

h= Planck constant, 

KT / 

„ 

D S R 

A = Ce 

----- (4.6) 

T= temperature on Kelvin Scale, and, 

h 

C= concentration of corrosion sites per m 2 of the surface. 

Tables (4.13-4.16) and Figs. (4.53-4.60) show the following results: 

1- Values of the activation energy (Ea) and the pre-exponential factor (A) 

had the same kinetic effects of the additives in both media and these were: 

a. for lead alloy and cured negative electrode in the un-stirred acid 

solution, the additive caused a decrease in Ea and A values as compared 

with the values in the absence of the additive, 

b. H3PO4 caused an increase in the values of Ea and A to maximum for 

grid lead in the both media. 

(149)

c. The lead alloy in the stirred acid solution and the cured positive 

electrode in the un-stirred solution in the presence of NaCl resulted in 

the maximum values of Ea and A. 

d. The (H3PO4+ FeSO4) mixture attained maximum values for Ea and 

A in the stirred oxygenated acid solution for the cured positive 

electrode. 

e. For cured negative electrode in the presence FeSO4 showed greatest 

values of Ea and A in stirred the acid solution. 

2- The minimum values of Ea and A were attained in such cases as: 

a. for lead alloy in the un-stirred acid solution in the presence of 

FeSO4, 

b. in the presence of FeSO4 in the stirred solution for the grid lead 

electrode, 

c. in the absence of additive for lead alloy in the stirred solution and 

for the cured positive electrode in the un-stirred acid solution, 

d. H3PO4 caused a decrease in Ea and values to minimum for the cured 

positive and negative electrodes in the both stirred and un-stirred media 

respectively, 

e. in the presence of (H3PO4 + FeSO4) mixture for the cured negative 

electrode in the stirred solution, 

f. for the grid lead electrode in the presence of NaCl in the un-stirred 

solution. 

Thus, the smaller activation energy of a reaction which was attained 

by additives (the lower the height of the energy barrier) the more rapid is 

the reaction at a given temperature, corrosion reaction proceeded on 

special surface sites starting on sites with low values of Ea and proceeded 

to others with higher Ea. (111,84) 

4- DS „ values in the presence of different amounts of additives shifted 

to more positive or to less negative values than the corresponding 

(150)

values in the absence of additives indicating a decrease in the rate 

corrosion of electrodes. 

Table (4.13):Values of activation Energies(Ea/k J mol -1 ) , preexponential 

factors(A/molecules cm -2 s -1 )and Entropy of 

activation(ΔS ≠ /J mol -1 K -1 ) for the corrosion of lead alloy working 

electrode in(0.56M) oxygenated H2SO4 solution in the presence and 


additive medium log A A Ea ∆S ≠ 

without 

additive 

H3PO4 

(11g dm -3 ) 

FeSO4 

(0.2g dm -3 ) 

+ 

H3PO4 

(11g dm -3 ) 

NaCl 

(4g dm -3 ) 

FeSO4 

(0.2g dm -3 ) 

un-stirred 19.57 3.71 X 10 +19 

stirred 9.47 2.96 X 10 +9 

un-stirred 14.03 1.08 X 10 +14 

stirred 10.75 5.58 X 10 +10 

un-stirred 14.15 

1.40 X 10 +14 

Stirred 12.06 1.12 X 10 +12 

un-stirred 17.78 6.09 X 10 +17 

stirred 12.36 2.28 X 10 +12 

un-stirred 9.13 1.35 X 10+9 

(151) 

38.09 129.55 

14.64 -64.71 

24.33 23.59 

16.59 -39.29 

24.65 

25.78 

20.06 -14.15 

34.33 95.39 

21.91 -8.46 

12.02 -70.22

stirred 11.29 1.95X 10 +11 

(152) 

18.34 -28.89

Table (4.14):Values of activation Energies(Ea/k J mol -1 ) , preexponential 

factors(A/molecules cm -2 s -1 ) and Entropy of 

activation(ΔS ≠ /J mol -1 K -1 ) for the corrosion of grid lead working 

electrode in (0.56M) oxygenated H2SO4 solution in the presence and 



without 

additive 

H3PO4 

(11g dm -3 ) 

FeSO4 

(0.2g dm -3 ) 

+ 

H3PO4 

(11g dm -3 ) 

NaCl 

(4g dm -3 ) 

FeSO4 

(0.2g dm -3 ) 

un-stirred 15.73 5.41 X 10 +15 

stirred 13.97 9.34 X 10 +13 

un-stirred 21.40 2.51 X 10 +21 

stirred 17.33 2.14 X 10 +17 

un-stirred 15.04 1.09 X 10 +15 

stirred 11.37 2.37 X 10 +11 

un-stirred 10.58 3.78 X 10 +10 

stirred 13.43 2.71 X 10 +13 

un-stirred 12.06 1.14 X 10 +12 

stirred 10.31 2.03 X 10 +10 

(153) 

28.56 56.14 

25.72 22.39 

42.34 164.58 

32.63 86.71 

26.82 42.84 

18.46 -27.28 

15.98 -42.53 

23.79 12.10 

19.49 -14.23 

16.05 -47.72

Table (4.15):Values of activation Energies(Ea/k J mol -1 ), preexponential 


activation(ΔS ≠ /J mol -1 K -1 ) for the corrosion of cured positive 


presence and absence of additives 


without 

additive 

H3PO4 

(11g dm -3 ) 

FeSO4 

(0.2g dm -3 ) 

+ 

H3PO4 

(11g dm -3 ) 

NaCl 

(4g dm -3 ) 

FeSO4 

(0.2g dm -3 ) 

un-stirred 4.52 3.30 X 10 +4 

stirred 9.29 1.82 X 10 +9 

un-stirred 5.93 8.45 X 10 +5 

stirred 7.82 6.59 X 10 +7 

un-stirred 5.07 1.16 X 10 +5 

stirred 12.46 2.86 X 10 +12 

un-stirred 11.91 8.14 X 10 +11 

stirred 11.48 3.05 X 10 +11 

un-stirred 5.95 8.89 X 10 +5 

stirred 8.36 2.29 X 10 +8 

(154) 

6.74 -158.48 

18.87 -67.77 

9.08 -131.54 

14.41 -95.33 

7.04 -148.02 

26.33 -6.58 

25.17 -17.03 

24.28 -25.18 

9.38 -131.11 

15.94 -84.98

Table (4.16):Values of activation Energies(Ea/k J mol -1 ), preexponential 


activation(ΔS ≠ /J mol -1 K -1 ) for the corrosion of cured negative 


presence and absence of additives. 


without 

additive 

H3PO4 

(11g dm -3 ) 

FeSO4 

(0.2g dm -3 ) 

+ 

H3PO4 

(11g dm -3 ) 

NaCl 

(4g dm -3 ) 

FeSO4 

(0.2g dm -3 ) 

un-stirred 12.40 2.54 X 10 +12 

stirred 3.98 9.54 X 10 +3 

un-stirred 4.39 2.45 X 10 +4 

stirred 4.78 6.03 X 10 +4 

un-stirred 5.68 4.77 X 10 +5 

stirred 3.32 2.10 X 10 +3 

un-stirred 9.56 3.61 X 10 +9 

stirred 6.33 2.12 X 10 +6 

un-stirred 4.86 7.22 X 10 +4 

stirred 11.77 5.95 X 10 +11 

(155) 

26.3 -7.58 

6.08 -168.80 

5.84 -160.97 

6.80 -153.47 

9.26 -136.29 

3.43 -181.37 

19.66 -62.06 

11.40 -123.89 

7.18 -151.98 

24.78 -19.63

(156)

(157)

(158)

(159)

(160)

(161)

(162)

(163)

The results of Figs.(4.61-4.62) indicate the existence of a linear 

relationship between the values of log A and the corresponding values of 

log A and the corresponding values of Ea, which may be expressed as (112) : 

Log A = mE + I ----- (4.7) 

where m and I are respectively the slope and intercept of the plots in 

Figs.(4.61-4.62) such a behaviour is referred to as “compensation effect” 

which describes the kinetics of a great number of catalytic and tarnishing 

reactions on metals (113,114) . Equation (4.7) indicates that simultaneous 

increase or decrease in Ea and log A for a system tend to compensate from 

the standpoint of the reaction rate. 

A number of interpretations 

(164) 

(115) have been offered for the 

phenomenon of the compensation effect in surface reaction, among which 

the effect could be ascribed to the presence of energetically heterogeneous 

reaction sites on the electrode surface, which suffered corrosion in the 

electrolytic solution. A decrease in Ea at constant log A implies a higher 

rate, while an increase in Ea at constant log A implies a lower rate; 

simultaneous increase in Ea and log A therefore tend to compensate from 

the standpoint of the corrosion rate. When such a compensate operates, it is 

possible for striking variations in Ea and log A through a series of surface 

sites on a metal or an alloy to yield only a small variation in reactivity.

(165)

(166)

5.1- Conclusions: 

The conclusions that could be drawn from the experimental results 

and the related discussions may be put as: 

1. The rate of corrosion was generally higher in the stirred oxygenated 

acid solution than in the corresponding unstirred deaerated media. 

2. The grid lead showed greatest tendency for corrosion while the cured 

negative electrode material had the least tendency for corrosion. 

3. The grid lead showed the lowest and the cured negative the greatest 

rate of corrosion in the stirred oxygenated acid solution. 

4. The higher protection efficiencies (p%) were attained for the 

corrosion of the working electrode materials in the stirred oxygenated 

acid solution than in the unstirred oxygenated acid solution in the 

presence of H3PO4 in the corrosion medium. 

5. The additives had an inhibiting effect on the corrosion of battery 

6. 

plates and components in the stirred and un-stirred oxygenated sulphuric 

acid solution and the corrosion potential shifted in the noble direction. 

The stimulating effect of the additives was noticed in the some cases in 

the presence of sodium chloride in the acid solution. 

The Gibbs free energy changes (DG) for the corrosion of the battery 

plates and components was always negative indicating the 

7. 

thermodynamic feasibility of the corrosion of the battery plates and 

components. The dependencies of such changes on temperature 

(-dDG/dt) were either negative or positive resulting either in negative or 

positive value of DH and DS for the corrosion process. 

The corrosion processes for battery plates and components in the 

absence or the presence of the various additives followed kinetically 

Arrhenius type rate equation. Positive values have been derived for the 

energy of activation (Ea). A linear relationship existed between the 

values at Ea and the logarithm of the pre- exponential factor (log A) 

suggesting the operation of a compensation effect in the kinetics of 

corrosion. 

١٦٦(

5.2- Suggestions for Future Research 

1. The corrosion medium may be extended to other concentrations of 

the sulphuric acid in the presence and the absence of different other salts 

and organic inhibitors. 

2. The corrosion investigations may be carried out for the same 

electrodes under stirred and un-stirred conditions of the corrosion 

medium which should also be subjected to the both aeration and 

deaeration conditions. 

3. The corrosion medium may also be subjected to thorough chemical 

analysis after corrosion tests in order to identify the types and extends of 

the various metallic ions that may be formed throughout anodic 

dissolution of the working electrode. 

4. The working electrodes may also be examined carefully by scanning 

electron microscope, ESCA and other sophisticated techniques 

subsequent to all the corrosion experiments. 

5. Other additives may be used in examining the corrosion behaviours 

of the electrodes and these may involve picric acid, boric acid and 

chromates. 

6. The additives may also be added to the paste or to the grid of battery 

plates and to the other battery components prior to corrosion 

experiments in the various corrosion media. 

١٦٧(

References 

1. R.J. Brodd, Batteries for cordless Appliances, (John Wiley and Sons, 

Inc. New York, 1987).P.(154-155). 

2. M. Silberberg, Chemistry, The Molecular Nature of Matter and 

change, (John Wiley and Sons, New York, 1996). 

3. H. Bode, Lead-Acid Batteries, (John Wiley and Sons, New York, 

London,1977). 

4. Gregory M.Williams,Chemistry,The Molecular Science,(John Wiley 

and Sons,Inc.New York 1999). 

5. D.A.J.R and , J. Power Sources, 1989,28, 107. 

6. M.Barak, Electrochemical Power Sources, (Stevenage, U.K., 1980). 

7. D. Linden, Handbook of Batteries and Fuel Cells, (McGraw-Hill 

Book Co, 1984). 

8. J.E.Dix, J. Power Sources , 1987, 19, 157. 

9. D.A.J. Rand , The Battery Man, 1987, September, 14. 

10. Kirk- Othmer, Encyclopedia of chemical Technology, 2 nd edition, 

(John Wiley and Sons, Inc. New York , 1964), vol.3. 

11. P. Scharf and R. Wagner, J. Power Sources, 2000, 35, 117. 

12. V.Iliv and D. Pavlor, J. Appl. Electrochem., 1979, 9, 555. 

13. T.Inoue and N. Koura, Electrochemistry , 2000, 68, 789. 

14. N.K. Grigaluk, J.Apply. Chem. USSR, 1979, 52, 742. 

15. B.K.Mahato, J. Electrochem. Soc., 1980, 127, 1679. 

16. G.J. Szava, J. Power Sources, 1988, 23, 119. 

17. G.W.Vinal, Storage Batteries, 4 th edition, (John Wiley and Sons, 

Inc. New York , 1955). 

18. R.J. Hill, J. Power Sources, 1983, 9, 55. 

19. D.Pavlov , E. Bashtavelova, J. Electrochem. Soc., 1984, 131, 1468. 

20. E. Bashtavelova, J. Electrochem. Soc., 1986, 133, 241 

(168)

21. D. Pavlov, J. Electrochem. Soc., 1992, 139, 3075. 

22. M.Dimitrov, J. Power Sources, 2001, 93, 234. 

23. D. Pavlov, and V. Iliev, J. Power Sources, 1981, 7, 153. 

24. V.Iliev and D.Pavlov, J.Appl. Electrochem., 1985, 15, 39. 


26. D. Pavlov, Power Source for Electric vehicles, B.D. McNicol, D.A. 

J. Rand . eds, Chapter 5. Lead Acid Batteries. P. 313-327. ( Elsevier, 

Amsterdam, 1984). 

27. N.Iordonov, J. Electrochem. Soc., 1970, 117, 9. 

28. L. Semynov, Storage Batteries, 1967, P. 78. 

29. E.S.Napoleon,J.Power Sources,1987,19,169. 

30. D.J.G.Ives, Reference Electrodes, (Acadeic Press, New York, 

London, 1961). 

31. Colin A. Vincent and B. Scrosati, Modern Batteries An Introduction 

to electrochemical Power Source, 1997, P. 145. 

32. D.Pavlov, Berichfe der Bunsengeselchaft, 1967, 71, 398. 

33. C.N. Poulieff and N. Iodanov, J. Electrochem. Soc., 1969,116, 316. 


35. S. Ruevski, J. Power Sources, 1990, 31, 217. 

36. D. Pavlov, G. Papazov, J. Electrochem. Soc., 1972, 119, 8. 

37. G. Papazov, J. Electrochem. Soc. , 1980, 127, 2104. 

38. E. Bashtavelova, J. Power Sources, 1990, 31, 243. 

39. D.Pavlov, J. Electroanal. Chem., 1976, 72, 319. 

40. V.Iliv, J. Electrochem. Soc., 1974, 121, 854. 

41. V.S. Bagotzky, Chemical Power Sources, (Academic Press, New 

York, London, 1980). 

42. R.J.Ball,J.Power Sources,20002,111,23. 

43. B. Monahov, J.Appl. Electrochem., 1993, 23, 1244. 

44. T. Laitinen, K. Salmi, Electrochem. Acta, 1991, 36, 605. 

(169)

45. D. Pavlov, B. Monahov, J. Electroanal. Chem., 1991, 305, 57. 

46. D.Pavlov,J.Appl.Electrochem.,1997,27,6. 

47. U.R. Evans, Metallic corrosion, Passivity and protection, (Arnold, 

London, 1947). 

48. A.T.Kuhn, The Electrochemistry of Lead, (John Wiley and Sons, 

Inc. New York, 1979). 

49. P.Ruestschi and R.T. Angstadt, J.Electrochem. Soc., 1964, 12, 111. 

50. W.H.Boctor, Proceding Corrosion Seminar, 13-16 Dec., (1976) 

Baghdad. 

51. G.Tedeschi, Mat. Nat., 1937, 25, 641. 

52. P. Delalay, M.Pourbaix, J. Electrochem. Soc., 1951, 98, 97. 

53. J.Lander, J. Electrochem Soc., 1951, 98, 6. 

54. J. Casey and K.M. Camprey, J. Electrochem Soc., 1955, 102, 219. 

55. G. Hohlstein and E. Pelzell, Metall., 1960, 14, 765. 

56. G.W. Vinal, Storage Batteries, (John Wiely Inc. 1962). 

57. A .A. Abdul Azim and K.M. El-Sobki, Corr. Sci., 1971, 11, 821. 

58. U.R. Evans, The corrosion and Oxidation of Metals., (Edward 

Arnold, 1971). 

59. P.Ruetschi, Electrochem. Acta., 1963, 8, 333. 

60. T. Rogachev, J.Power Sources, 1988, 23, 4. 

61. G. Papazov, J. Power Sources, 1983, 10,3. 

62. R.H.Newnham, D.A.J.Rand, J. Power sources, 1995, 53, 93. 

63. Guo-Lin Wei, Jia-Rong Wang, J. Power sources, 1994, 52, 25. 

64. W.A.Badaway, S.S.El-Egamy, J.Power Sources, 1995, 55, 11. 

65. Takao. Omae, J.Power Sources, 1997, 65,2. 

66. W.H. Bactor, S.Zhong, J. Power Sources, 1999, 77, 56. 

67. D. Slavkov, J. Power Sources, 2002, 112, 199. 

68. J.A. Van Frawnhofer and G.H. Banks , potentiostat and Its 

Applications, (Butter Worths, London, 1972). 

(170)

69. J.O.M. Bockris and A. K. Reddy, Modern Electrochemistry , Press, 

New York, 1970), Vol. 2, P. 1315. 

70. A. I. Karim, M.Sc. Thesis, College of Science, University of 

Baghdad, Jan., (2003). 

71. Kh. S. Abed, Ph. D. Thesis, College of Science, University of 

Baghdad, October, 1997. 

72. Q.A. Yousif, M.Sc. Thesis, College of Science, University of 

Baghdad, July,(2001). 

73. N.A. Hikmat, Ph. D. Thesis, College of Science, University of 

Baghdad, Jan., 2002. 

74. N.D. Green, Experimental Electrode Kinetics, (Troy, New York, 

1965), P. 64. 

75. J.W.D. France, Mat. Res., 1969, 9,21. 

76. S.Glasstone,Principle of Elrctrochemistry,Van Nastrand, New York, 

1942,P.448. 

77. American Society for Testing and material, Annual Book of ASTM 

standard, 1980, Part 10. 

78. American Society for Testing and Material Annual Book of ASTM 

Standard, 1978-G5 

79. H.H.Uhlig, Corrosion and Corrosion Control, (Wiley, New York), 

(2000), P. 411. 

80. L. L. Shrier (ed.), Corrosion; Metal/Environment Reactions, (Butter 

Worths, Boston, Mass., 1978), Vol.1. 

81. F. Mansfeld, Corrosion science, 1973, 29, 397. 

82. Stern. M., and Roth, J. Electrochem.Soc., 1957, 104, 390. 

83. E. Heitz and W. Schwenk, Br. Corros. J., 1976, 11, 2. 

84. 

85. I.G. Murgulessue and O. Radorici, 2 nd -Inter. Congr. Metal corrosion, 

(London, 1961), P. 202-205. 

(171)

86. A.M. Farhan, Ph.D., Thesis, College of Science, University of 

Baghdad, June, 2000. 

87. W.J. Lorenz and F. Mansfeld , Proc. 8 th . Intr. Congr. Of Metal 

88. 

Corrosion (Dechema,Germany, 6-11 September, 1981). 

89. B.N. Kabanov, Electrochemica, Acta, 1964, 9, 1197. 

90. J. Lander, J. Electrochem. Soc., 1951, 98, 213. 

91. Pierre R. Roberge, Handbook of Corrosion Engineering, (Mc Graw- 

Hill, New York, 1999). 

92. G.B. Roger, Determination of pH (Wiley, New York, 1972), P. 307. 

93. L.M. Al-Shama’a , Ph. D., Thesis, College of Science, University of 

Baghdad, April, 1999. 

94. J.O.M. Bockris and A. K. Reddy, Modern Electrochemistry , Press, 

New York, 1970), P.176. 

95. Mars G. Fontana and Norbert D. Greene, Corrosion Engineering, 

(Mc Graw-Hill, New York, 1978), P. 319. 

96. H.Y. Chen, Journal of Power Sources, 2000, 88, 78. 

97. E. Rocca, J. Electronal. Chem. 2003, 543, 153. 

98. K.R. Trethewey and J. Chamberlain, Corrosion for science and 

Engineering , 2 nd . ed. (Addision Wesley Longman Ltd. 1996). 

99. M. G. Fontana, N.D. Green, Corrosion Engineering, 2 nd Edn., 

(McGraw-Hill, New York, 1963). 

100. W.H. Boctor, J. Electrochem. Soc., 1976, 123, 12. 

101. K.R. Bullock and D.H. Mcclelland, J. Electrochem. Soc., 1976, 123, 

327. 

102. W. Visscher, J. Power Sources, 1977, 1, 257. 

103. K.R. Bullock, J. Electrochem. Soc., 1979, 126, 3. 

104. 

105. E. Kunse and K. Schwabe, Corrosion Sci., 1964, 15, 419. 

(172)

106. A.M. Farhan, M.Sc., Thesis, College of Science, University of 

107. 

Baghdad, 1989. 

108. G. Chond, Catalysis by Metals, (Academic Press, New York, 1962), 

p.140. 

109. Y.K. Al-Haydari, J.M. Saleh and M.H. Matloob, J. Phys. Chem. , 

1985, 89, 3286. 

110. S.A. Isa and J.M. Saleh, J. Phys. Chem., 1972, 76, 2530. 

111. E.Cremer, Advances in Catalysis, (Academic Press, New York, 1955) 

vol 7, p. 75. 

112. H.H.Uhlig, Corrosion and Corrosion Control, (Wiley, New York, 

2000), P. 74-76. 

113. M. Stern and A.L. Grary , J. Electrochem Soc., 1957, 56, 104. 

114. K.R. Trethewey and J. Chamberlain, Corrosion for Science and 

Engineering, 2 nd . ed. (Addision Wesley Longman Ltd. 1996). 

115. T.A. Sakman, Thesis, College of Science, Saddam University, 

January, 1996. 

116. Driver, R., and Meakins, R.J., Br. Corros. J., 1974, 9, 227. 

117. Jsseling, F.P., Corros. Sci., 1974, 14, 97. 

118. D. Pavlov and N. Kapkov, J. Electrochem. Soc., 1990, 137, 28. 

119. L.A. Beckctaeva and K.V. Rybalka, J. Power Sources, 1990, 32, 143. 

120. R.J. Hill, J. Power Sources, 1988, 22, 175. 

(173)

ﺔﺻﻼﺨﻟﺍ 

ﻦﻣ ﺝﺫﺎﻤﻧ ﺔﻌﺒﺳ ﻞﻛﺄﺘﻟ ﻲﺑﺎﻄﻘﺘﺳﻻﺍ ﻙﻮﻠﺴﻟﺍ ﺔﺳﺍﺭﺩ ﺔﻟﺎﺳﺮﻟﺍ ﻉﻮﺿﻮﻣ ﻝﻭﺎﻨﺘﻳ 

ﺹﺎﺻﺮﻟﺍ ﺓﺪﻴﻀﻧ ﺕﺎﻧﻮﻜﻣﻭ ﺡﺍﻮﻟﺍ ﺔﻋﺎﻨﺻ ﻲﻓ ﺔﻣﺪﺨﺘﺴﻤﻟﺍ ﺏﺎﻄﻗﻻﺍ 

: ﻲﻫﻭ ﺔﻴﻀﻣﺎﺤﻟﺍ 

. ﺹﺎﺻﺮﻟﺍ ﺔﻜﻴﺒﺳ ﺐﻄﻗ -۱ 

. ﺹﺎﺻﺮﻟﺍ ﻚﺒﺸﻣ ﺐﻄﻗ -۲ 

. ﻲﻘﻨﻟﺍ ﺹﺎﺻﺮﻟﺍ ﺐﻄﻗ 

-۳ 

. ﺮﻤﻌﻤﻟﺍ ﺮﻴﻏ ﺐﺟﻮﻤﻟﺍ ﺐﻄﻘﻟﺍ -٤ 

.ﺮﻤﻌﻤﻟﺍ 

ﺐﺟﻮﻤﻟﺍ ﺐﻄﻘﻟﺍ -٥ 

.ﺮﻤﻌﻤﻟﺍ ﺮﻴﻏ ﺐﻠﺴﻟﺍ ﺐﻄﻘﻟﺍ -٦ 

.ﺮﻤﻌﻤﻟﺍ ﺐﻟﺎﺴﻟﺍ ﺐﻄﻘﻟﺍ -۷ 

ﻝﻮﻣ ( 0.56,0.25,0.1) 

ﺰﻴﻛﺍﺮﺘﺑ ﻚﻴﺘﻳﺮﺒﻜﻟﺍ ﺾﻣﺎﺣ ﻝﻮﻠﺤﻣ ﻲﻓ ﺎﻫﺮﻤﻏ ﺪﻨﻋ 

ﻰﻟﺍ ۲۹۸ ﻦﻣ ﺖﺣﻭﺍﺮﺗ ﺓﺭﺍﺮﺤﻟﺍ ﺕﺎﺟﺭﺩ ﻦﻣ ﻯﺪﻣ ﻰﻠﻋ ﺐﻌﻜﻤﻟﺍ ﺮﺘﻤﺳ ﺪﻠﻟ 

ﺔﻌﺑﺭﺍ ﻰﻟﺍ ﺔﺳﺍﺭﺪﻠﻟ ﺔﻴﻠﻤﻌﻟﺍ ﺔﻐﻴﺼﻟﺍﻭ ﻡﺎﻌﻟﺍ ﻂﻤﻨﻟﺍ ﻢﻴﺴﻘﺗ ﻦﻜﻤﻳﻭ ﻦﻔﻠﻛ ۳۱۸ 

: ﻲﺗﺄﻳ 

ﺎﻤﻛﻭ ﻡﺎﺴﻗﺍ 

ﻂﺳﻭ ﻲﻓ ﻦﻴﺠﺴﻛﻷﺍﺯﺎﻏ ﺩﻮﺟﻮﺑ ﺝﺫﺎﻤﻨﻠﻟ ﻲﺑﺎﻄﻘﺘﺳﻻﺍ ﻙﻮﻠﺴﻟﺍ ﺔﺳﺍﺭﺩ -ﺃ 

.ﻞﻛﺄﺘﻟﺍ 

ﻮﺟ ﻲﻓﻭ ﻦﻴﺠﺴﻛﻭﻷﺍ ﺯﺎﻏ ﺩﻮﺟﻮﺑ ﺝﺫﺎﻤﻨﻠﻟ ﻲﺑﺎﻄﻘﺘﺳﻻﺍ 

ﻙﻮﻠﺴﻟﺍ ﺔﺳﺍﺭﺩ – ﺏ 

. ﻞﻛﺎﺘﻟﺍ ﻂﺳﻮﻟ ﻲﻜﻳﺮﺤﺗ 

ﻂﺳﻭ ﻲﻓ ﻦﻴﺟﻭﺮﺘﻨﻟﺍﺯﺎﻏ ﺩﻮﺟﻮﺑ ﺝﺫﺎﻤﻨﻠﻟ ﻲﺑﺎﻄﻘﺘﺳﻻﺍ ﻙﻮﻠﺴﻟﺍ ﺔﺳﺍﺭﺩ -ﺝ 

.ﻞﻛﺄﺘﻟﺍ 

ﻮﺟ ﻲﻓﻭ ﻦﻴﺟﻭﺮﺘﻨﻟﺍ ﺯﺎﻏ ﺩﻮﺟﻮﺑ ﺝﺫﺎﻤﻨﻠﻟ 

ﻲﺑﺎﻄﻘﺘﺳﻻﺍ ﻙﻮﻠﺴﻟﺍ ﺔﺳﺍﺭﺩ – -ﺩ 

. ﻞﻛﺎﺘﻟﺍ ﻂﺳﻮﻟ ﻲﻜﻳﺮﺤﺗ 

ﺩﺎﻬﺠﻤﻟﺍ ﺯﺎﻬﺟ ﻡﺍﺪﺨﺘﺳﺎﺑ ﺝﺫﺎﻤﻨﻠﻟ ﻲﺑﺎﻄﻘﺘﺳﻻﺍ ﻙﻮﻠﺴﻟﺍ ﺔﺳﺍﺭﺩ ﺖﻤﺗ -۱ 

ﻦﻣ ﻞﺼﺤﺘﺴﻤﻟﺍ( CORROSCRIPT)ﻰﻤﺴﻤﻟﺍ( 

Potentiostat) 

ﻲﻧﻮﻜﺴﻟﺍ 

ﻰﻠﻋ ﻝﻮﺼﺤﻟﺍ ﻪﺘﻄﺳﺍﻮﺑ ﻦﻜﻣﺃﻭ ﺔﻴﺴﻧﺮﻔﻟﺍ( Taccussel) 

ﻞﻴﺳﻮﻛﺎﺗ ﺔﻛﺮﺷ 

ﺩﻮﻬﺠﻟﺍ ﻦﻣ ﻯﺪﻣ ﻰﻠﻋ( Polarization Curves) 

ﺏﺎﻄﻘﺘﺳﻻﺍ ﺕﺎﻴﻨﺤﻨﻣ 

Scan ) ﺢﺴﻣ ﺔﻋﺮﺳ ﻝﺎﻤﻌﺘﺳﺄﺑ ﺖﻟﻮﻓ+2.0 

ﻰﻟﺍ-2.0 

ﻦﻣ ﺖﺣﻭﺍﺮﺗ 

ﺔﻘﻴﻗﺪﻟﺍ ﻲﻓ ﺮﺘﻤﻠﻣ 30 ﺖﻐﻠﺑ ( x-y Recorder) 

ﻞﻴﺠﺴﺘﻟﺍ ﺯﺎﻬﺠﻟ( Rate 

ﺢﺒﺼﻳ( Ec) 

ﻞﻛﺄﺘﻟﺍ ﺪﻬﺟ ﻥﺃ ﺔﻠﺼﺤﺘﺴﻤﻟﺍ ﺞﺋﺎﺘﻨﻟﺍ ﻦﻣ ﻦﻴﺒﺗ ﺪﻗﻭ ( mm/min) 

ﻂﺳﻭ ﻲﻓ 

ﻦﻴﺟﻭﺮﺘﻨﻟﺍﺯﺎﻏ ﺩﻮﺟﻮﺑ ﻚﻴﺘﻳﺮﺒﻜﻟﺍ ﺾﻣﺎﺣ ﻝﻮﻠﺤﻣ ﻲﻓ ﺔﻴﺒﻟﺎﺳﺮﺜﻛﺃ

ﻥﺃﻭ ﻙﺮﺤﺘﻣ ﻂﺳﻭ ﻲﻓ ﻦﻴﺠﺴﻛﻭﻻﺍ ﺯﺎﻏ ﺩﻮﺟﻮﺑ ﺔﻴﺒﻟﺎﺳ ﻞﻗﺃﻭ ﻙﺮﺤﺘﻣ ﺮﻴﻏ 

ﻚﻴﺘﻳﺮﺒﻜﻟﺍ ﺾﻣﺎﺣ ﻲﻓ ﺔﻴﻟﺎﻋ ﺖﻧﺎﻛ ﺎﻣﻮﻤﻋ ( ic) 

ﻞﻛﺄﺘﻟﺍ ﺭﺎﻴﺗ ﺔﻓﺎﺜﻛ ﺕﺍﺮﻴﻐﺗ 

ﺮﻴﻏ ﻦﻴﺟﻭﺮﺘﻨﻟﺍ ﻮﺠﺑ ﺔﻧﺭﺎﻘﻣ ﻙﺮﺤﺘﻣ ﻮﺟ ﻲﻓﻭ ﻦﻴﺠﺴﻛﻭﻻﺍ ﺯﺎﻏ ﺩﻮﺟﻮﺑ 

.ﺎﻀﻔﺨﻨﻣ ( ic) 

ﺮﻴﻐﺗ ﺎﻬﻴﻓ ﻥﺎﻛ ﻲﺘﻟﺍﻭ ﻙﺮﺤﺘﻤﻟﺍ 

:ﻰﻠﻋ ﺖﻠﻤﺘﺷﺃ ﺕﺎﻓﺎﻀﻤﻟﺍ ﻦﻣ ﺩﺪﻋ ﺮﻴﺛﺄﺗ ﺔﺳﺍﺭﺩ ﺖﻤﺗ -۲ 

.(ﺐﻌﻜﻤﻟﺍ ﺮﺘﻤﺳﺪﻠﻟ ﻢﻏ۱۱)ﻚﻳﺭﻮﻔﺳﻮﻔﻟﺍ 

ﺾﻣﺎﺣ -۱ 

ﺕﺎﺘﻳﺮﺒﻛ ﻊﻣ ( ﻢﻏ۱۱) 

ﻚﻳﺭﻮﻔﺳﻮﻔﻟﺍ ﺾﻣﺎﺣ ﻦﻣ ﺞﻳﺰﻣ -۲ 

. ﺐﻌﻜﻤﻟﺍ ﺮﺘﻤﺴﻠﻟ (ﻢﻏ0.2)ﺯﻭﺪﻳﺪﺤﻟﺍ 

.(ﺐﻌﻜﻤﻟﺍﺮﺘﻤﺳﺪﻠﻟ ﻢﻏ4) 

ﻡﻮﻳﺩﻮﺼﻟﺍ ﺪﻳﺭﻮﻠﻛ -۳ 

.(ﺐﻌﻜﻤﻟﺍ ﺮﺘﻤﺳﺪﻠﻟ ﻢﻏ0.2)ﺯﻭﺪﻳﺪﺤﻟﺍ 

ﺕﺎﺘﻳﺮﺒﻛ -٤ 

ﺩﻮﺟﻭ ﻲﻓ ﻱﺭﻻﻮﻣ( 0.56) 

ﻚﻴﺘﻳﺮﺒﻜﻟﺍ ﺾﻣﺎﺤﻟ ﻲﺘﻴﻟﻭﺮﺘﻜﻟﻷﺍ ﻝﻮﻠﺤﻤﻟﺍ ﻲﻓ 

ﺏﺎﻄﻗﻻﺍ ﻦﻣ ﺔﻔﻠﺘﺨﻣ ﺝﺫﺎﻤﻧ ﺔﻌﺑﺭﺃ ﻰﻠﻋ ﻦﻛﺎﺳﻭ ﻙﺮﺤﺘﻣﻮﺟﻭ ﻦﻴﺠﺴﻛﻭﻻﺍ 

: ﻲﺗﺎﻳ ﺎﻤﻛﻭ 

.ﺹﺎﺻﺮﻟﺍ ﺔﻜﻴﺒﺳ ﺐﻄﻗ -۱ 

.ﺹﺎﺻﺮﻟﺍ ﻚﺒﺸﻣ ﺐﻄﻗ -۲ 

.ﺮﻤﻌﻤﻟﺍ ﺐﺟﻮﻤﻟﺍ ﺐﻄﻘﻟﺍ -۳ 

.ﺮﻤﻌﻤﻟﺍ ﺐﻟﺎﺴﻟﺍ ﺐﻄﻘﻟﺍ -٤ 

ﺕﺎﺑﺎﺴﺣ ﺖﻟﺩ ﺪﻗﻭ ﻦﻔﻠﻛ( 318-298)ﻦﻣ 

ﺔﻳﺭﺍﺮﺤﻟﺍ ﺕﺎﺟﺭﺪﻟﺍ ﻯﺪﻣ ﻲﻓ 

ﺔﻳﺎﻤﺣ ﻰﺼﻗﺍ ﻍﻮﻠﺑ ﻰﻠﻋ ( Protection Efficiency)ﺔﻳﺎﻤﺤﻟﺍ 

ﺔﻳﺎﻔﻛ 

ﺔﻨﻜﻤﻣ ﺔﻳﺎﻤﺣ ﻰﻧﺩﺍﻭ ﻚﻳﺭﻮﻔﺳﻮﻔﻟﺍ ﺾﻣﺎﺣ ﻂﺒﺜﻤﻟﺍ ﻝﺎﻤﻌﺘﺳﺎﺑ ﺔﻨﻜﻤﻣ 

.ﺏﺎﻄﻗﻻﺍ ﻊﻴﻤﺟ ﻰﻟﺍ ﺔﺒﺴﻨﻟﺎﺑ ﺪﻳﺭﻮﻠﻛ ﻝﺎﻤﻌﺘﺳﺄﺑ 

( ∆S،∆H،∆G)ﻞﻛﺄﺘﻟﺍ 

ﺕﻼﻋﺎﻔﺘﻟ ﺔﻴﻜﻴﻤﻨﻳﺍﺩﻮﻣﺮﺜﻟﺍ ﺕﺎﻴﻤﻜﻟﺍ ﺖﺒﺴﺣ -۳ 

ﺔﻗﺎﻁ ﻢﻴﻗ ﻥﺃ ﺔﺳﺍﺭﺪﻟﺍ ﺕﺮﻬﻅﺃ ﺪﻗﻭ ﺕﺎﻓﺎﻀﻤﻟﺍ ﺩﻮﺟﻭﻭ ﺏﺎﻴﻏ ﺔﻟﺎﺣ ﻲﻓ 

ﻲﻓ ﻲﻀﻣﺎﺤﻟﺍ ﻂﺳﻮﻟﺍ ﻲﻓ ﺔﻴﺒﻟﺎﺳ ﺮﺜﻛﺃ ﻡﻮﻤﻌﻟﺍ ﻰﻠﻋ ﺖﻧﺎﻛ ∆G ﺓﺮﺤﻟﺍ ﺰﺒﻴﻛ 

ﺔﺳﺍﺭﺪﻟﺍ ﺕﺮﻬﻅﺄﻓ ﺕﺎﻓﺎﻀﻤﻟﺍ ﺩﻮﺟﻭ ﺔﻟﺎﺣ ﻲﻓ ﺎﻣﺃ، ﻦﻴﺟﻭﺮﺘﻨﻟﺍ ﺯﺎﻏ ﺩﻮﺟﻭ 

ﺔﻴﺒﻟﺎﺳ ﻞﻗﺃﻭ ﻚﻳﺭﻮﻔﺳﻮﻔﻟﺍ ﺾﻣﺎﺣ ﺩﻮﺟﻭ ﻲﻓ ﺔﻴﺒﻟﺎﺳ ﺮﺜﻛﺃ ﺖﻧﺎﻛ ∆Gﻢﻴﻗ 

ﻥﺃ 

ﻢﻴﻗ ﻲﻓ ﺕﺍﺮﻴﻐﺗ ﺕﺪﺟﻭ ﺎﻤﻛ. ﻡﻮﻳﺩﻮﺼﻟﺍ ﺪﻳﺭﻮﻠﻛ ﺩﻮﺟﻭ ﻲﻓ 

ﻲﻓ ﻦﻳﺎﺒﺗ ﺙﻭﺪﺣ ﻰﻠﻋ ﺮﻴﻐﺘﻟﺍ ﺍﺬﻫ ﻝﺪﻳﻭ ﻅﻮﺤﻠﻣ ﺭﺍﺪﻘﻤﺑ ( ∆S) 

ﻲﺑﻭﺮﺘﻧﻻﺍ 

ﺔﺟﺭﺩ ﻰﻠﻋ ﻞﻛﺄﺘﻟﺍ ﺔﻴﻠﻤﻌﻟﺍ ﺓﺮﺤﻟﺍ ﺔﻗﺎﻄﻟﺍ ﺕﺍﺮﻴﻐﺗ ﺔﻳﺩﺎﻤﺘﻋﺍ ﻯﺪﻣﻭ ﻉﻮﻧ 

ﺕﺍﺮﻴﻐﺗ ﺙﻭﺪﺣ ﻰﻟﺍ ( ∆S) 

ﻲﺑﻭﺮﺘﻧﻻﺍ ﻢﻴﻗ ﺕﺍﺮﻴﻐﺗ ﺕﺩﺃﻭ. ﺓﺭﺍﺮﺤﻟﺍ 

.ﺎﻀﻳﺃ ( ∆H) 

ﻲﺒﻟﺎﺜﻧﻻﺍ ﻲﻓ ﺓﺮﻅﺎﻨﻣ 

ﻡﺪﻋﻭ ﺩﻮﺟﻭ ﺔﻟﺎﺣ ﻲﻓ ﻞﻛﺄﺘﻟﺍ ﺕﻼﻋﺎﻔﺗ( Kinetics)ﺕﺎﻴﻛﺮﺣ 

ﺖﻌﻀﺧ -٤ 

ﻦﻴﺑ ﺔﻴﻄﺧ ﺔﻗﻼﻋ ﺩﻮﺟﻮﺑ ﻲﻀﻘﺗ ﻲﺘﻟﺍ ﺱﻮﻨﻳﺭﺃ ﺔﻟﺩﺎﻌﻤﻟ ﺕﺎﻓﺎﻀﻤﻟﺍ ﺩﻮﺟﻭ

ﺔﻘﻠﻄﻤﻟﺍ ﺓﺭﺍﺮﺤﻟﺍ ﺔﺟﺭﺩ ﺏﻮﻠﻘﻣﻭ( Log ic) 

ﻞﻛﺄﺘﻟﺍ ﺔﻋﺮﺳ ﻢﺘﻳﺭﺎﻏﻮﻟ ﻢﻴﻗ 

Energy ,Ea) 

ﻂﻴﺸﻨﺘﻟﺍ ﺔﻗﺎﻁ ﻢﻴﻗ ﺏﺎﺴﺣ ﺎﻬﻨﻣ ﻦﻜﻣﺃ ﻲﺘﻟﺍﻭ ( 1/T) 

( pre-exponential,A)ﻲﺳﻻﺍ 

ﺭﺍﺪﻘﻤﻟﺍ ﻕﻮﺒﺴﻣ ﻢﻴﻗﻭ ( Activation 

ﻦﻣ ﻦﻴﺒﺗ ﺎﻤﻛ( Entropy of Activation, ∆S≠) 

ﻲﺸﻨﺘﻟﺍ ﻲﺑﻭﺮﺘﻧﺍﻭ 

Log ) ﻲﺳﻻﺍ ﺭﺍﺪﻘﻤﻟﺍ ﻕﻮﺒﺴﻣ ﻢﺘﻳﺭﺎﻏﻮﻟ ﻦﻴﺑ ﺔﻴﻄﺧ ﺔﻓﻼﻋ ﺩﻮﺟﻭ ﺔﺳﺍﺭﺪﻟﺍ 

ﻥﺄﺑ ﺔﻴﻄﺨﻟﺍ ﺔﻗﻼﻌﻟﺍ ﻩﺬﻫ ﻝﺪﺗﻭ.ﺎﻬﻟ ﺓﺮﻅﺎﻨﻤﻟﺍ( Ea) 

ﻂﻴﺸﻨﺘﻟﺍ ﺔﻗﺎﻁ ﻢﻴﻗﻭ ( A 

ﺡﺍﻮﻟﺃ ﺝﺫﺎﻤﻧ ﺢﻄﺳ ﻰﻠﻋ ﺔﻨﻳﺎﺒﺘﻣ ﻊﻗﺍﻮﻣ ﻰﻠﻋ ﺙﺪﺤﻳ ﻞﻛﺄﺘﻟﺍ ﻞﻋﺎﻔﺗ 

ﻥﺃﻭ ﻂﻴﺸﻨﺘﻟﺍ ﺔﻗﺎﻁ ﻢﻴﻗ ﺚﻴﺣ ﻦﻣ ﺔﻴﻀﻣﺎﺤﻟﺍ ﺹﺎﺻﺮﻟﺍ ﺓﺪﻴﻀﻧ ﺕﺎﻧﺍﻮﻜﻣﻭ 

ﺮﺸﺘﻨﻳ ﻢﺛ ﺔﺌﻁﺍﻭ ﻂﻴﺸﻨﺗ ﺔﻗﺎﻄﺑ ﻊﺘﻤﺘﺗ ﻲﺘﻟﺍ ﻊﻗﺍﻮﻤﻟﺎﺑ ﻻﻭﺃ ﺍﺪﺒﻳ ﻞﻛﺄﺘﻟﺍ ﻞﻋﺎﻔﺗ 

.ﻰﻠﻋﺃ ﻂﻴﺸﻨﺗ ﺕﺎﻗﺎﻄﺑ ﻊﺘﻤﺘﺗ ﻲﺘﻟﺍ ﻊﻗﺍﻮﻤﻟﺍ ﻰﻟﺍ ﺎﻬﻨﻣ

ﺩﺍﺪﻐﺑ ﺔﻌﻣﺎﺟ 

ﻡﻮﻠﻌﻟﺍ ﺔﻴﻠﻛ 

ءﺎﻴﻤﻴﻜﻟﺍ ﻢﺴﻗ 

ﺔﻴﻀﻣﺎﺤﻟﺍ ﺹﺎﺻﺮﻟﺍ ﺓﺪﻴﻀﻧ ﺡﺍﻮﻟﺍ ﻞﻛﺂﺗ 

ﻲﻓ 

ﻚﻴﺘﻳﺮﺒﻜﻟﺍ ﺾﻣﺎﺣ 

ﻰﻟﺍ ﺔﻣﺪﻘﻣ ﺔﻟﺎﺳﺭ 

ﺔﺟﺭﺩ ﻞﻴﻧ ﺕﺎﺒﻠﻄﺘﻣ ﻦﻣ ءﺰﺠﻛ ﺩﺍﺪﻐﺑ ﺔﻌﻣﺎﺠﺑ ﻡﻮﻠﻌﻟﺍ ﺔﻴﻠﻛ 

ءﺎﻴﻤﻴﻜﻟﺍ ﻲﻓ ﻡﻮﻠﻋ ﺮﻴﺘﺴﺟﺎﻤﻟﺍ 

ــﻫ۱٤۲٥ 

ﻞﺒﻗ ﻦﻣ 

ﺪـــــﻤﺣ 

ﻞﻛﺎﻛ ﺭﺎﻴﺘﺨﺑ 

ﺱﻮﻳﺭﻮﻟﺎﻜﺑ 

۲۰۰۰ 

ﻥﺎﺒﻌﺷ

Corrosion of Lead-Acid Battery Electrodes in Sulphuric Acid

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