CHEM02200704003 Nilamadhab Pandhy - Homi Bhabha National ...

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Chapter 7 6 Duplex Ti-TiO 2 coated 304L SS showed lower capacitance and higher polarization resistance as compared to both Ti and TiO 2 coatings in both 1 M and 8 M nitric acid exhibiting excellent corrosion resistance. The protection efficiency was 97 % in 1 M nitric acid, and 84 % in 8 M nitric acid, respectively. 7 The improvement in corrosion resistance of duplex Ti-TiO 2 coating as compared to Ti and TiO 2 single layer coatings on 304L SS is attributed to the effective minimization of structural heterogeneities, and formation of uniformly distributed particles enhancing passivation property. The results of the present investigation on “Role of passivity and surface modification on the corrosion behaviour of AISI 304L stainless steel in nitric acid medium” using surface morphological studies, analytical examinations, and electrochemical investigations is as summarized below. Passivity of AISI 304L SS at low concentration of 0.1 M and 0.5 M nitric acid starts initially with the formation of adsorbed chromium hydroxide species which appears in the form of platelet like structures on the surface. The hydroxide layer at lower concentration is electroinactive and provides protective film from aggressive environment of nitric acid. With increase in concentration to 0.6 M nitric acid, the hydroxide layer changes over to oxide layer, and during this platelet like structures forms homogenous oxide layer on the surface. With still rise in concentration of nitric acid to 1 M the protective oxide film depletes from structural heterogeneous areas leading to opening up of oxide boundaries. The depletion of oxide layer at structural heterogeneous areas initiate selective dissolution as well as localized corrosion in 304L SS.
Chapter 7 Sub-surface modification using nitrogen ion implantation on 304L SS brings structural and compositional changes on the surface which significantly increases the localized corrosion resistance in the oxidizing environment of nitric acid. The factors responsible for the improvement in corrosion resistance are homogenization of the surface, enrichment of nitrogen and formation of selective chromium nitride (Cr 2 N) phase. Thus the beneficial aspect nitrogen on the corrosion resistance is well reflected from the study on corrosion behaviour of nitrogen ion implanted 304L SS in nitric acid medium. Top surface modification using Titanium (Ti) layer gives good corrosion performance in 1 M nitric acid. The oxide film developed is stable enough to resist attack at structural heterogeneous areas. At higher concentration of 8 M nitric acid, the oxidizing action in the pores and intergranular boundaries increases which decreases the protection efficiency and performance of the 304L SS. Titanium dioxide gives improved corrosion performance as compared to titanium coating in both low (1 M) and high (8 M) concentration of nitric acid despite presence of pores and other structural heterogeneities. This is mainly due to presence of perfect stoichiometric oxide with good passivation property. Even though TiO 2 shows good corrosion performance, uniform dissolution of the coating can be observed at 8 M nitric acid. Duplex Ti-TiO 2 coating is extremely effective for corrosion protection in both low (1 M) and high concentration (8 M) of nitric acid as compared to Ti and TiO 2 coatings due to combination of good passivation property of titanium dioxide and minimization of structural heterogeneities by Ti interlayer. The percentage of protection efficiency and performance is far superior to both the single layer coatings. Top surface modification is more effective than sub-surface modification for corrosion protection because of easy optimization of microstructure by tunable reduction of pores and other structural heterogeneities on the surface.
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2.3 Effect of alloying elements on
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6.2.3.2 Open circuit potential vs.
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eprocessing can be recovered, and c
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The ex-situ study of passive film w
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Fig.3.10: Schematic of electrical e
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Fig.6.11: Polarization study of unc
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AISI: American Institute of Steel I
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Chapter 1 C H A P T E R 1 Spent Nuc
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Chapter 1 1.3 Challenges in spent n
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Chapter 1 corrosion resistance. The
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Chapter 1 choice of zirconium is du
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C H A P T E R2
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Chapter 2 temperature, (c) higher i
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Chapter 2 Chromium in excess of 12
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Chapter 2 2. 3 Effect of alloying e
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Chapter 2 The twins are identified
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Chapter 2 and at temperature around
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Chapter 2 of adsorption of oxygen o
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Chapter 2 transpassive dissolution
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Chapter 2 healing chromium oxide fi
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Chapter 2 their segregation to the
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Chapter 2 is intimately related to
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Chapter 2 in nature because the dis
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C H A P T E R3
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Chapter 3 3.1.1.2 Specimen preparat
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Chapter 3 ionized. However, differe
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Chapter 3 various industrial applic
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Chapter 3 In the present investigat
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Chapter 3 3.1.3.2 Atomic force micr
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Chapter 3 present on the surface fo
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Chapter 3 necessary condition is th
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Chapter 3 Y m is the sputter yield.
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Chapter 3 Fig. 3.7: Schematic of X-
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Chapter 3 rate of 10Å/min using 5
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Chapter 3 different doses of nitrog
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Chapter 3 The modulus of electroche
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Chapter 3 equivalent circuit as sho
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Chapter 3 reference electrode with
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Chapter 3 for understanding the pas
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C H A P T E R4
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Chapter 4 encountered by all materi
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Chapter 4 pitting, and intergranula
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Chapter 4 The ridged structure, and
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Chapter 4 nitric acid is that the b
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Chapter 4 Potential (V) Vs Ag/AgCl
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Chapter 4 4.2.3 In-situ electrochem
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Chapter 4 The surface morphologies
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Chapter 4 a b c d Opening up of gra
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Chapter 4 Intensity (Arbitrary unit
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Chapter 4 The chromium, and oxygen
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Chapter 4 Intensity (Arbitrary unit
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C H A P T E R5
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Chapter 5 elements, and often impar
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Chapter 5 5.2 Results and discussi
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Chapter 5 Presence of oxygen is due
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Chapter 5 was an increase in marten
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Chapter 5 formation of Cr 2 N was a
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Chapter 5 electrochemical environme
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Chapter 5 N + Dose E corr (mV vs. A
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Page 142 and 143: Chapter 6 The change over from capa
Page 144 and 145: Chapter 6 The impedance parameters
Page 146 and 147: Chapter 6 Conc. Substrate condition
Page 148 and 149: Chapter 6 6.6a-d. The uncoated spec
Page 150 and 151: Chapter 6 (55.18°) respectively, w
Page 152 and 153: Chapter 6 OCP shifted in noble dire
Page 154 and 155: Chapter 6 The high phase angle over
Page 156 and 157: Chapter 6 Fig. 6.10d: Log f vs. Log
Page 158 and 159: Chapter 6 Fig. 6.11b: Polarization
Page 160 and 161: Chapter 6 Covalent aspect of lattic
Page 162 and 163: Chapter 6 As compared to uncoated s
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Page 166 and 167: Chapter 6 Similarly, the plots for
Page 168 and 169: Chapter 6 for the duplex coating, a
Page 170 and 171: Chapter 6 Fig.6.16b: Polarization s
Page 172 and 173: Chapter 6 6.2.3.5 Morphological exa
Page 174 and 175: Chapter 7 C H A P T E R 7 The cha
Page 176 and 177: Chapter 7 1. Surface morphology exa
Page 180 and 181: Chapter 7 EC-SPM study on effect
Page 183 and 184: [1] Baldev Raj, U. Kamachi Mudali,
Page 185 and 186: [37] G. Okamoto, T. Shibata, Corros
Page 187 and 188: [79] M. Moens, M. Van Craen, F.C. A
Page 189 and 190: [117] R.E.Williford, C.F.Windisch J
Page 191 and 192: [157] N. Mottu, M. Vayer, R. Erre,
Page 193: [197] M. Metikos Hukovic, M. Ceraj
Page 196 and 197: [19] H. H. Uhlig, Corros Sci, 19 (1
Page 198 and 199: [57] J. F. Ziegler, J. P. Biersack,
Page 200 and 201: [97] I. Betova, M. Bojinov, V. Kara
Page 202 and 203: [139] V. Ashworth, R. P. M. Procter
Page 204 and 205: [176] G. Frankel, G. Grundmeier, H.
Page 207 and 208: List of publications 1. Referred
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CHEM02200704003 Nilamadhab Pandhy - Homi Bhabha National ...

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