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UNIVERSITI TEKNIKAL MALAYSIA MELAKA<br />
CORROSION BEHAVIORS OF TOOL STEEL IN TANNIC ACIDS<br />
This report is submitted in accordance with requirement of the Universiti Teknikal<br />
Malaysia Melaka (UTeM) for the Bachelor Degree of Manufacturing Engineering<br />
(Engineering Materials) with Honours.<br />
By<br />
YEOH SENG FU<br />
FACULTY OF MANUFACTURING ENGINEERING<br />
2010
UNIVERSITI TEKNIKAL MALAYSIA MELAKA<br />
BORANG PENGESAHAN STATUS LAPORAN PROJEK SARJANA MUDA<br />
TAJUK: Corrosion Behaviors of Tool Steel in Tannic Acids<br />
SESI PENGAJIAN: 2009/2010<br />
Saya YEOH SENG FU (B050610153)<br />
mengaku membenarkan Laporan PSM ini disimpan di Perpustakaan Universiti<br />
Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat kegunaan seperti berikut:<br />
1. Laporan PSM adalah hak milik Universiti Teknikal Malaysia Melaka dan penulis.<br />
2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan<br />
untuk tujuan pengajian sahaja dengan izin penulis.<br />
3. Perpustakaan dibenarkan membuat salinan laporan PSM ini sebagai bahan<br />
pertukaran antara institusi pengajian tinggi.<br />
4. **Sila tandakan (√)<br />
SULIT<br />
TERHAD<br />
TIDAK TERHAD<br />
(TANDATANGAN PENULIS)<br />
Alamat Tetap:<br />
7,Taman Sri Delima, JLN Jenun,<br />
06700 Pendang, Kedah<br />
Tarikh: 09 th APRIL 2010.<br />
(Mengandungi maklumat yang berdarjah keselamatan<br />
atau kepentingan Malaysia yang termaktub di dalam<br />
AKTA RAHSIA RASMI 1972)<br />
(Mengandungi maklumat TERHAD yang telah ditentukan<br />
oleh organisasi/badan di mana penyelidikan dijalankan)<br />
Disahkan oleh:<br />
(TANDATANGAN PENYELIA)<br />
Cop Rasmi:<br />
Tarikh: _______________________<br />
** Jika Laporan PSM ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi<br />
berkenaan dengan menyatakan sekali sebab dan tempoh PSM ini perlu dikelaskan sebagai SULIT atau<br />
TERHAD.
DECLARATION<br />
I hereby, declared this thesis entitled “Corrosion Behaviors of Tool Steel in Tannic<br />
Acids” is the results of my own research except as cited in references.<br />
Signature : ………………………………………….<br />
Author’s Name : YEOH SENG FU<br />
Date : 09 th APRIL 2010
APPROVAL<br />
This report is submitted to the Faculty of Manufacturing Engineering of UTeM as<br />
a partial fulfillment of the requirements for the degree of Bachelor of<br />
Manufacturing Engineering (Engineering Materials) with Honours. The member<br />
of the supervisory committee is as follow:<br />
(Signature of Supervisor)<br />
………………………………<br />
(Official Stamp of Supervisor)
APPROVAL<br />
This report is submitted to the Faculty of Manufacturing Engineering of UTeM as<br />
a partial fulfillment of the requirements for the degree of Bachelor of<br />
Manufacturing Engineering (Engineering Materials) with Honours. The member<br />
of the supervisory committee is as follow:<br />
(Signature of Principal Supervisor)<br />
……………………………….<br />
(Official Stamp of Principal Supervisor)<br />
(Signature of Co-Supervisor)<br />
……………………………….<br />
(Official Stamp of Co-Supervisor)
ABSTRACT<br />
The purpose of this project is to analyze the corrosion behavior of cutting tool<br />
material use in the wood industry which cause by tannic acid. According to the wood<br />
species and type of metallic materials, the wear of woodcutting tools is very<br />
different. The metallic nature of cutting tools, water and water-soluble components in<br />
the wood will cause an electrochemical mechanism of corrosion. Both mechanical<br />
wear and electrochemical action are responsible of the total wear of metallic tools.<br />
Therefore, the objective of this study is to characterize the electrochemical action of<br />
the wood medium on the corrosion of the woodcutting tool materials. It identifies the<br />
composition element in steel that influence the corrosion behavior. Usually, tannic<br />
acid extracts from various plants and will react with the iron to form ferrous-tannates<br />
as rust on steel. The method starts with preparing the tannic acids solution in<br />
different concentration and immersed the carbon steel blade in tannic solution. The<br />
parameter like pH, concentration and temperature changes in experiment to<br />
investigate how it affects the corrosion behavior. In order to evaluate composition<br />
element affect corrosion behavior, six type specimens (carbon steel and tungsten<br />
carbide) need to immerse in tannic acids for certain time. Then, it will apply Gamry<br />
Instrument Framework Software to carry out corrosion test for finding its corrosion<br />
rate, corrosion resistance and corrosion potential of corroded system. From data<br />
obtain, the pH of tannic begin decrease when temperature reaches 60°C and thus<br />
increase corrosion rate. Result shows that the material that have highest chromium<br />
(>4%) have lowest corrosion rate. Mostly, tungsten carbide has high corrosion<br />
resistance than carbon steel. Chemical reaction between tannins and iron produce<br />
blue black deposits of iron (III) tannates complexes on surface material. As a result,<br />
pitting corrosion occurs as a small hole on that material after several hours.<br />
i
ABSTRAK<br />
Tujuan projek ini adalah untuk mengkaji sifat kekasian logam alat pemotong pokok<br />
yang diguna dalam kilang kayu disebabkan tannic acids. Dengan merujuk kepada<br />
jenis pokok kayu dan bahan logam, kekasian logam alat pemotong pokok adalah<br />
berbeza. Kehadiran bahan logam, cecair dan bahan cecair pelarut dalam pokok kayu<br />
boleh menyebabkan tindak balas kimia Kedua-dua kakisan logam dan tindak balas<br />
kimia adalah penyebab kepada kakisan alat logam. Oleh itu, tujuan projek ini adalah<br />
untuk mencari factor-faktor kimia yang menyebabkan tindak balas kakisan logam<br />
dalam pokok tannic acids dengan alat logam. Ini akan mengakaji komposisi bahan<br />
terkandung dalam logam yang boleh menyebabkan kakisan alat pemotong logam.<br />
Biasanya, tannic acids diambil daripada pelbagai jenis pokok dan akan bertindak<br />
balas dengan logam untuk membentuk ferrous tannates sebagai kakisan dalam<br />
logam. Kaedah project ini dimulakan dengan penyediaan pelbagai kepekatan tannic<br />
acids dan rendaman karbon logam ke cecair tannins. Parameter seperti pH, kepekatan<br />
dan suhu akan berubah dalam experiment untuk mengkaji bagaimana kakisan logam<br />
berlaku. Untuk mencari komposisi bahan yang menpengaruhi kakisan, enam sample<br />
karbon logam dan tungsten carbide diperlukan untuk merendam dalam tannic acids<br />
untuk beberapa jam. Kemudaian, Gamry Instrument Framework Software akan<br />
digunakan untuk mengkaji kakisan logam terutamanya kadar kakisan, rintangan<br />
kakisan dan keupayaan kakisan. Keputusan data menunjukan pH tannic akan<br />
berkurang apabila suhu mencapai 60°C dan ini akan menyebabkan kadar kakisan<br />
meningkat. Hasil experiment menunjukan bahan yang mempunyai komposisi<br />
chromium (>4%) tinnggi akan ada yang kadar kakasin yang rendah. Biasanya,<br />
tungsten carbide mempunyai ringtangan kakisan yang tinngi berbanding karbon<br />
logam. Tindak-balas kimia antara tannic dan ferum menghasilkan mendakan biru<br />
hitam ferum(III) tannates pada permukaan bahan tersebut. Ini menyebabkan, pitting<br />
kaksian yang ada lubang kecail berlaku pada bahan tersebut selepas beberapa jam.<br />
ii
DEDICATION<br />
For my beloved family<br />
iii
ACKNOWLEDGEMENT<br />
I would like to extend my warmest gratitude to my supervisor, Dr. Zulkifli bin Mohd<br />
Rosli for his excellent supervision, invaluable guidance, advice and assistance<br />
towards me throughout this project. Besides, he also gives me some important<br />
guidance on how to write a good report.<br />
I would also like to express my deepest appreciation to classmate for their supporting<br />
and help me solve the problem along this project. They always give me some theory<br />
or information especially in contributing and sharing ideals towards this project.<br />
Besides, I also not forget the technician that guide me on how using the apparatus<br />
and equipment to process this project. Sometimes, this project also helps by senior of<br />
my course. He always shares their previous experience to me especially in this<br />
corrosion field study. Without their support and assistance, I cannot carry out this<br />
project properly.<br />
Finally, I would like to thanks to my family whose give encouragement and support<br />
until I have strength and inspiration to carry out this project with my best ability.<br />
iv
TABLE OF CONTENT<br />
Abstract i<br />
Abstrack ii<br />
Dedication iii<br />
Acknowledgement iv<br />
Table of Content v<br />
List of Tables ix<br />
List of Figures x<br />
List Abbreviations xii<br />
1.0 CHAPTER 1: INTRODUCTION 1<br />
1.1 Project Overview 1<br />
1.2 Background 2<br />
1.3 Objective 3<br />
1.4 Scope 3<br />
1.5 Problem Statement 3<br />
1.6 Importance of Study 4<br />
2.0 CHAPTER 2: LITERATURE REVIEW 5<br />
2.1 Definition of Tannins 5<br />
2.1.1 Classification of Tannins 6<br />
2.1.2 Chemical Behavior of Tannic Acids 8<br />
2.2 Detection of Tannins 9<br />
2.2.1 Sources of Tannins 9<br />
2.2.2 Tannins in Different Woods 9<br />
2.3 Utilization of Tannins 12<br />
2.4 Wood Cutting Tool Material 13<br />
2.4.1 Tungsten Carbide Steel Alloy 13<br />
2.4.2 Example of Wood Cutting Tool Material 14<br />
2.4.3 Corrosion Behavior from Wood Cutting Industry 15<br />
2.4.4 Alloying Elements for Cutting Tool Material 16<br />
v
2.4.5 Microstructure of different Carbon Steel Alloy 17<br />
2.4.6 Relationship between Chromium and Corrosion Rate 18<br />
2.5 Corrosion Mechanism in Tannic Acids Solutions 18<br />
2.6 SEM of Cutting Tool Material 22<br />
2.6.1 Carbon Steels in Tannic Acids 22<br />
2.6.2 Tungsten Carbide in Tannic Acids 23<br />
2.7 Pitting Corrosion 23<br />
2.7.1 Determination Extent of Pitting <strong>24</strong><br />
2.7.2 Loss in Mechanical Properties 26<br />
2.8 Planning and Preparation of Corrosion Tests 26<br />
2.8.1 Electrochemical techniques 26<br />
2.8.2 Electrochemical Methods of Corrosion Testing 27<br />
2.8.2.1 Electrochemical Polarization Experiment 28<br />
2.8.3 Immersion Tests 29<br />
2.8.3.1 Total Immersion 29<br />
3.0 CHAPTER 3: METHODOLOGY 30<br />
3.1 Introduction 30<br />
3.2 Process Flow Chart 31<br />
3.3 PH Development of Tannin at Elevated Temperature 32<br />
3.3.1 Preparing Tannic Acid Solution 32<br />
3.3.1.1 Description of Ingredients in Tannic Acid Solution 33<br />
3.3.2 Experimental Procedure 33<br />
3.3.3 Summary 34<br />
3.4 Corrosion Test Analysis 35<br />
3.4.1 Experiment Setup 36<br />
3.4.2 Gamry Framework Software 37<br />
3.4.3 Tafel Technique 37<br />
3.4.3.1 Tafel Technique Analysis 38<br />
3.4.3.2 Calculation of corrosion rate 39<br />
3.4.3.3 Tafel Extrapolation 40<br />
3.4.4 Polarization Resistance Technique 40<br />
3.5 Determination of Extent Pitting 42<br />
3.5.1 Mass Loss Measurement 42<br />
vi
3.6 Microstructure Analysis 43<br />
3.7 Planning of Results and Discussion 44<br />
3.8 Planning of Conclusion and Recommendation 44<br />
4.0 CHAPTER 4: RESULTS AND DISCUSSION 45<br />
4.1 Introduction 45<br />
4.2 PH Development of Tannin at Elevated Temperature 46<br />
4.2.1 PH Development Tannin at 60°C Different Concentration 46<br />
4.2.2 PH Development Tannin at 90°C Different Concentration 47<br />
4.2.3 PH Tannin against Concentration for Different Temperature 48<br />
4.2.4 PH Tannin against Temperature for Different Immersed Time 49<br />
4.3 Corrosion Test Analysis 50<br />
4.3.1 Corrosion Behavior of Carbon Steel 51<br />
4.3.1.1 Corrosion Current Density by Tafel Technique 52<br />
4.3.2 Corrosion Behavior of Tungsten Carbide Alloys 55<br />
4.3.2.1 Corrosion Current Density by Tafel Technique 57<br />
4.3.3 Calculation of Corrosion Rate 60<br />
4.4 Determination of Extent Pitting 64<br />
4.4.1 Mass Loss Measurement 64<br />
4.5 Microstructure Analysis 65<br />
4.6 Corrosion Mechanism in Tannic Acids 68<br />
4.6.1 Corrosion Surface Behavior Carbon Steel Experiment II 68<br />
4.6.2 Corrosion Surface Behavior of Carbon Steel Blade 69<br />
4.7 Corrosion Chemical Reaction 69<br />
5.0 CONCLUSION AND RECOMMENDATIONS 71<br />
5.1 Conclusion 71<br />
5.2 Recommendation and Future Research 73<br />
REFFERENCES 75<br />
vii
APPENDICES<br />
A Carbon Steel A Tafel Graph Data<br />
B Carbon Steel B Tafel Graph Data<br />
C Carbon Steel C Tafel Graph Data<br />
D Tungsten Carbide A Tafel Graph Data<br />
E Tungsten Carbide B Tafel Graph Data<br />
F Tungsten Carbide C Tafel Graph Data<br />
G Material and Equipment<br />
H Gantt Chart PSM I<br />
I Gantt Chart PSM II<br />
J ASTM G102<br />
K MSDS OF Tannic Acids<br />
viii
LIST OF TABLES<br />
2.1 Tannin Concentration and PH Value of Different Wood Types 10<br />
2.2 Tannin Content by Wood Type 11<br />
2.3 Woodworker Exposure to Airborne of Tannins 11<br />
2.4 List of Alloying Steel Element 16<br />
2.5 C and Cr Content of the Materials Tested 17<br />
2.6 Microscopically Pit Depth Measurements 25<br />
3.1 Carbon Steel Composition 35<br />
3.2 Tungsten Carbide Alloy Composition and Amount of Binders 35<br />
4.1 Corrosion Potential and Corrosion Current Density of Carbon Steel 54<br />
4.2 Corrosion Potential and Corrosion Current Density of Tungsten Carbide 58<br />
4.3 Mass Loss Measurement Data 64<br />
ix
LIST OF FIGURES<br />
2.1 Gallic acid and Hexahydroxydiphenic Acid 7<br />
2.2 Chemical Structure of the Different Groups of Tannin 7<br />
2.3 Classifications of Tannins 8<br />
2.4 Various Shape of Tungsten Carbide Tool 14<br />
2.5 Pitting Corrosion in Steel Blades in the Wood Cutting Industry 15<br />
2.6 Cemented Tungsten Carbide for Tooling Microstructure 15<br />
2.7 Microstructures of Analyzed Carbon Steel 17<br />
2.8 Corrosion-Rates of Materials Influence by Cr Content 18<br />
2.9 Tannin Corroded Carbon Steel View by Microscope 19<br />
2.10 Microscopic Image of Carbon Steel Corroded in Tannin for 3 hours 19<br />
2.11 SEM + EDS Grain Boundary Corrosion (X52CrMoV8-1) 20<br />
2.12 SEM + EDS Tannin–Fe Complex (X52CrMoV8-1) 20<br />
2.13 SEM of Carbon Steel before Immersion 22<br />
2.14 SEM of Carbon Steel before and after Immersion 22<br />
2.15 SEM and Metallographic Cross-Section of the Tungsten Carbide after<br />
Immersed in Tannic Acids for <strong>24</strong> hours 23<br />
2.16 Variations in the Cross-Sectional Shape of Pits. <strong>24</strong><br />
2.17 Cross Section of Pit used for Depth Measurements 25<br />
2.18 Schematic Electrochemical Potential-Current Relationships for Corroding<br />
System 27<br />
2.19 Schematic Diagram of Polarization Cell 28<br />
3.1 The Process Flow Chart of Project 31<br />
3.2 Some Ingredient use to form Tannic Acids Solution 32<br />
3.3 PH Meter, Tannic Acid Solution and Carbon Steel blade in Experiment 33<br />
3.4 Process Flow Chart of Experiment I 34<br />
3.5 Specimen of Different Carbon Steel and Tungsten Carbide CuttingTool 35<br />
3.6 Typical Electrochemical Polarization Cell 36<br />
3.7 Apparatus Set-Up for Corrosion Test 36<br />
3.8 Gamry Framework Software and Parameter Setup Screen 37<br />
x
3.9 Experimentally Measured Tafel Polarization Plot 40<br />
3.10 Scale and Carbon Steel Blade before Cutting 42<br />
3.11 Cutting Tool Material is Immersed in Closed Equipment for 5 hours 43<br />
3.12 Disc Polishing and Etching Room 43<br />
3.13 Nital Acids use to Etching the Sample and Optical Microscope 44<br />
4.1 PH Value Development of Tannin at 60°C 46<br />
4.2 PH Value Development of Tannin at 90°C 47<br />
4.3 PH Value Development of Tannin Dependent from Start Concentration 48<br />
4.4 pH value decrement of Tannin increases rapidly at Higher Temperatures 49<br />
4.5 Evolution of Rp Value for Carbon Steel during 6 hours in Tannic Acids 51<br />
4.6 Evolution of Ecorr Value for Carbon Steel during 6 hours in Tannic Acids 51<br />
4.7 Tafel Plot Graph for Carbon Steel A 53<br />
4.8 Tafel Plot Graph for Carbon Steel B 53<br />
4.9 Tafel Plot Graph for Carbon Steel C 54<br />
4.10 Evolution of Rp for Tungsten Carbide Alloy at 6 hours in Tannic Acids 55<br />
4.11 Evolution of Ecorr for Tungsten Carbide Alloy 6 hours in Tannic Acid 56<br />
4.12 Comparison Rp Value of Carbon Steel and Tungsten Carbide 56<br />
4.13 Tafel Plot Graph for Alloy A 57<br />
4.14 Tafel Plot Graph for Alloy B 57<br />
4.15 Tafel plot Graph for Alloy C 58<br />
4.16 Comparison of Electrode Potential of Carbon Steel and Tungsten Carbide 59<br />
4.17 Comparison Log Current Density of Carbon Steel and Tungsten Carbide 59<br />
4.18 Comparison between Corrosion Rates of All Specimens 63<br />
4.19 Carbon Steel Microstructure after in Tannins for 1 hour and 5 hour 65<br />
4.20 Tungsten Carbide Microstructure before and after in Tannins for 5 hours 66<br />
4.21 Microstructure of Tannins Corroded Carbon Steel Blade Surface after<br />
5 hours at Magnification of 10x and 100x 66<br />
4.22 Carbon Steel before and after Immersed in Tannic Acids for 5 Hours 68<br />
4.23 Tungsen Carbide Sample before and after Immersed in Tannic Acids for<br />
5 Hours 68<br />
4.<strong>24</strong> Carbon Steel Blade that Corroded by Tannins after 5 Hours 69<br />
xi
%wt Percentages Weight<br />
LIST OF ABBREVIATIONS<br />
ASTM American Society for Testing and Materials<br />
C Carbon<br />
Cr Chromium<br />
CR Corrosion Rate<br />
Ecorr Corrosion Potential<br />
EDS Energy Dispersive X-ray Spectroscopy<br />
EIS Electrochemical Impedance Spectroscopy<br />
Fe Iron<br />
HRC Rockwell Hardness C-Scale<br />
Icorr Corrosion Current Density<br />
mv mile volt<br />
Rp Polarization Resistance<br />
SEM Scanning Electron Microscopy<br />
UV Ultraviolet<br />
xii
CHAPTER 1<br />
INTRODUCTION<br />
This chapter is to briefly explain the major information of whole project is carrying<br />
out. Overall, it summarized the progress of the whole project which describing on<br />
how the project has been done.<br />
1.1 Project Overview<br />
Generally, the main purpose of project is to investigate corrosion behavior of tool<br />
steel in tannic acid from the plant. The whole project is emphasis on composition of<br />
the cutting tool blade in tannic acids and how it affected by temperature, pH and<br />
concentration. The aim of this research is to characterize the corrosion behavior of<br />
different steels in various wood processing environments. To carry out this project,<br />
the understanding of characteristic of tannic acid and composition element in<br />
material are significant aspect.<br />
Moreover, the estimation method of corrosion data from Gamry Instrument<br />
Framework Software using Tafel Technique and Polarization Resistance method is<br />
very crucial. Before starting up with experiment, concentration of tannic acid and<br />
composition of sample require verify because different concentration of tannins will<br />
give different corrosion behavior.<br />
The experimental procedure of this project is divided into three main categories<br />
which are sample preparation, corrosion test and data analysis. This project was carry<br />
out via Tafel Technique and Polarization Resistance method by immerse the sample<br />
in different concentration and temperature of tannic acid. After sample preparation,<br />
1
the sample surface was analyzed by optical microscopy. It was to identify the surface<br />
behavior of the sample before corrosion and after corrosion. The comparison<br />
between corrosion current density and corrosion resistance sample needs to be<br />
justified. Tafel graph will be used to represent result and microstructure of sample<br />
will view in optical microscope. Mass loss measurement will be measure to obtain<br />
degradation rate of carbon steel blade in tannins solution.<br />
Finally, Tafel and Polarization Resistance graph are interpreted and several<br />
justifications will make base on result obtain. Moreover, discussion on requirement<br />
of composition element material is included in order to produce a good cutting tool<br />
for wood industry. Recommendation and future research are discussed in this work.<br />
1.2 Background<br />
Basically, tannic acid is a class of natural, non-toxic and biodegradable organic<br />
compound which is extracted from plant sources. However, this tannic acids will<br />
cause the corrosion appear at wood cutting tools when use to sawing the plant.<br />
According to wood species and type of metallic materials, the wear of wood cutting<br />
tools is very different. The metallic nature of cutting tools, water and water-soluble<br />
components in wood will cause an electrochemical mechanism of corrosion. Both<br />
mechanical wear and electrochemical action are responsible of the total wear of<br />
metallic tools. Therefore, objective of this study is to characterize electrochemical<br />
corrosion action of wood medium with wood cutting tool materials.<br />
Usually, both mechanical and corrosive mechanisms are responsible for corrosion of<br />
wood cutting tools. The determination of each relative magnitude mechanism is a<br />
challenge for wood industry attempting to improve and to adapt the quality of cutting<br />
tools. For example, machining of a wood known as “acid” like oak generally<br />
generates a tool wear greater than machining of a wood which having a pH nearly 7.<br />
The wood moisture and multi component nature of cutting tools also play an<br />
important role in kinetics of tools degradation. The aim of this study is to<br />
characterize the electrochemical degradation part of the tools in contact with a wood<br />
medium which prepared from plant.<br />
2
1.3 Objective<br />
i. To analyze the corrosion behavior of cutting tool material (carbon steel and<br />
tungsten carbide) in tannic acid by electrochemical method<br />
ii. To determine corrosion rate of tool steel by using Polarization Resistance and<br />
Tafel Technique under Gamry Instrument Framework Software<br />
iii. To evaluate the effect of pH, concentration and temperatures of tannin acids<br />
to the corrosion behavior of cutting tool material<br />
iv. To identify composition element in cutting tool material that influence its<br />
1.4 Scope<br />
corrosion behavior<br />
The scope of this project is study about the corrosion mechanism of the cutting tool<br />
in the wood industry which cause by tannic acids. The sample uses are three different<br />
types of carbon steel and tungsten carbide. The tannic acids will be prepared in<br />
different type solution. This sample will be immersed in tannic acids for different<br />
temperature. The corroded samples were viewed by optical microscope. The all<br />
corrosion test is control under Gamry Instrument Framework Software with Tafel<br />
Technique and Polarization Resistance Method. Through Tafel graph, the data can<br />
interpret from the Tafel plot such as corrosion current density and corrosion potential<br />
of corroded system. Analysis on corroded microstructure will include in this project.<br />
1.5 Problem Statement<br />
Obviously, the cutting tools in the wood industry often suffer from corrosion. These<br />
is due to wood industry are poor knowledge on degradation phenomenon of tools in<br />
contact with wood. It shows that different woods have a different corrosive impact. It<br />
is very difficult to know which type of cutting tool to use for sawing the various type<br />
of wood which contain different concentration tannic acid. So, it is important to learn<br />
more about the corrosive agent of different woods.<br />
3
Usually, the cutting process in industry will cause high temperature because the<br />
friction occurs between the cutting blade and wood. As a result, the corrosion rate<br />
will increase. Therefore, it is needed to evaluate on how the corrosiveness of tannins<br />
changes relative to temperature. It also require investigating how improve the<br />
understanding of material composition and parameter that affect corrosion to<br />
enhance the corrosion resistance against tannin.<br />
The large number of parameters related to machining with different wood materials<br />
hinders the evolution in wear of tools. The determination of the relative magnitude of<br />
each mechanism is a challenge for wood industry attempting to improve and to adapt<br />
the quality of cutting tools. For example, the machining of a wood known as “acid”<br />
like oak generally generates a tool wear greater than the machining of a wood that<br />
having a pH close to 7. Therefore, wood moisture and multi-component nature of<br />
cutting tools also play an important role in the kinetics of tools degradation. So both<br />
mechanical and corrosive mechanisms are responsible of wear of wood cutting tools<br />
Besides, the high cost of the high alloy steel also cause the industry wood to use tool<br />
steel although high alloy steel have higher corrosion resistance properties. So, the<br />
selection type of tool steel is very important to give maximum protection against<br />
tannic acids. In order to solve this problem, the study about the composition in tool<br />
steel use and their function in each element in composition is very significant<br />
because it will affect corrosion behavior.<br />
1.6 Importance of Study<br />
This project is significant for the wood industry in order to increase their lifetime of<br />
cutting tool. Based on the problem, the parameter that affects corrosion behavior of<br />
cutting tool needs to be identified. The selection type of cutting tool is very important<br />
in order to obtain maximum protection. Therefore, the study of composition and its<br />
element in wood cutting tool material is very significant.<br />
4
CHAPTER 2<br />
LITERATURE REVIEW<br />
This chapter consists of information which related to the study such as the theory and<br />
method that had been used by the others in order to investigate the corrosion<br />
behavior of tool steel in tannic acids. This information is important because it will<br />
lead to this study applicability until complete. In this research, it also the best way to<br />
guide and face the problem encountered during the completion of this study.<br />
2.1 Definition of Tannins<br />
The term “tannins” is no longer strange in chemistry field. It is comes from the<br />
ancient Celtic word for oak which is a typical source of tannins for leather making<br />
(Bisanda et al., 2003). According to Khanbabaee and Van Ree (2001), the name<br />
“tannin” is derived from the French word „Tanin‟ which means a tanning substance<br />
that used for a range of natural polyphenols. The ancient society had been using<br />
tannins to convert animal skin to form leather which are able to interact and<br />
precipitate proteins including the protein found in animal skin (Hagerman, 2002). In<br />
nature, the tannins are found worldwide in many different families of the higher<br />
plants such as in chestnut, pine and oak wood.<br />
Tannins are secondary metabolites that widely found in plant kingdom and it produce<br />
by condensation of simple phenolics (Chavan et al., 2001). Although tannins<br />
themselves are secondary phenolic metabolites, their chemical reactivities and<br />
biological activities have distinguished them from other plant of secondary phenolics<br />
(Hagerman, 2002).<br />
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Many researchers have tried to define tannins based on their structures, chemical<br />
reactivity and biological activities. However, the complexity of tannins has hindered<br />
their efforts to provide an appropriate definition for tannins. Batesmith and Swain<br />
(1962) have defined tannins as water soluble phenolics with molecular weights<br />
between 300 and 3000 Daltons (Da) which can exhibit usual phenolic reactions and<br />
showing the ability to precipitate alkaloids, gelatins and other proteins. However, this<br />
definition does not include all tannins since tannins with higher molecular weight of<br />
up to 20000 Da have been isolated. Griffith (1991) described tannins as<br />
“macromolecular phenolic substances” and divided them into two main group which<br />
are hydrolysable tannins and condensed tannins. Haslam (1989) is tried to emphasize<br />
the multiplicity of phenolic group characteristic of tannins for substitute the term<br />
“polyphenol” for “tannin”. He noted that tannins with molecular weight up to 20000<br />
Da have been reported and tannins complex not only with proteins and alkaloids but<br />
with certain polysaccharides as well.<br />
Tannins acid which is a class of natural, non-toxic and biodegradable organic<br />
compound is extracted from plant sources (Rahim et al., 2005). It have been<br />
suggested as a suitable replacement as corrosion inhibitor in aqueous media,<br />
component of rust converters, pigment in paint coating, corrosion inhibitor of<br />
reinforcing steel in concrete, chemical cleaning agents for removing iron-based<br />
deposited and oxygen scavenger for boiler water treatment system.<br />
2.1.1 Classification of Tannins<br />
Tannins are classified into two broad groups which is<br />
i. Hydrolysable ( Gallic Tannins and Ellagic Tannins)<br />
ii. Condensed tannins (Proanthocyanidine)<br />
Figure 2.1 (a) represent the chemical structure of Gallic acid and (b) represent the<br />
structure of Ellagic acids. Hydrolysable tannins are presented in oak tree and<br />
chestnut (5-10%). Condensed tannins are derived from Catechine and are present in<br />
the bark of oak tree (6-17%) or spruce (10-18%).<br />
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(a) (b)<br />
Figure 2.1: (a) Gallic acid and (b) Hexahydroxydiphenic acid<br />
Source: Winkelmann et al. (2006).<br />
Based on the molecular structures, Khanbabae and Van Ree (2001) suggested that<br />
tannins can be divided into four major groups which are Gallotannins, Ellagitannins,<br />
complex tannins and condensed tannins as show in the Figure 2.3. Their chemical<br />
structures are described as follow:<br />
i. Gallotannins are tannins in which galloyl units or their metadepsidic<br />
derivatives are bound to diverse polyol, catechin and ortriterpenoid units.<br />
ii. Ellagitannins are tannins in which at least two galloyl units are C-C<br />
coupled to each other and not contain a glycosidically link catechin unit.<br />
iii. Complex tannins are tannins in which a catechin unit is bound<br />
glycosidically to a gallotannin or an ellagitannin unit.<br />
iv. Condensed tannins are all oligomeric and polymeric proanthocyanidins<br />
formed by linkage of C-4 of one catechin with C-8 or C-6 of the next<br />
monomeric catechin (Khanbabaee and Van Ree, 2001).<br />
Figure 2.2: Chemical Structure of the different groups of Tannin: (a) Condensed Tannin, (b)<br />
Hydrolyzable Tannin. Source: Winkelmann et al. (2006).<br />
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