CHEM02200704003 Nilamadhab Pandhy - Homi Bhabha National ...

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Chapter 6 OCP shifted in noble direction for titanium dioxide coated 304L SS specimens as compared to uncoated, and Ti coated specimen. The shift of OCP in noble direction in both the concentration of test solutions clearly indicates greater protecting power of TiO 2 coating in the oxidizing environment of nitric acid as compared to uncoated, and Ti coated specimens. As compared to Ti coated specimens, TiO 2 coated specimens showed mostly steady state with increase in immersion time. This is largely due to the presence of perfect stoichiometeric oxide layer on the surface as compared to Ti which in general forms a number of sub-stoichiometric oxides in the oxidizing environment [197]. Nevertheless, marginal increase or decrease in OCP prior to attaining of steady state in both the test solutions indicates stability of the coatingelectrolyte interface by filling up of pinholes, pores, and void space at the inter-columnar boundaries [22]. The increase in OCP is attributed to the greater passivation tendency of TiO 2 in the auto-catalytic oxidizing environment of nitric acid leading to inhibition of anodic process as compared to Cr 2 O 3 film which naturally occurs on stainless steel surface. In general, TiO 2 is thermodynamically more stable over a wide potential region due to high lattice energy of formation as compared to Cr 2 O 3 [201]. In the eventuality of film dissolution, subsequent hydrolysis of the dissolved ions readily forms the TiO 2 film due to low free energy of formation in solution [201,202]. Ti 4+ + 2 H 2 O TiO 2 + 4 H + Thus, its healing power is also quite high, unlike Cr 2 O 3 [Cr(III)] where the film transfers to a soluble Cr 2 O 2- 7 [Cr(VI)] form in the oxidizing environment. For uncoated specimen, OCP in 8 M HNO 3 was higher as compared to 1 M HNO 3 because of large concentration of aqueous nitrous acid (HNO 2 ) produced at higher concentration, which imposes higher redox potential to the electrochemical environment. Thus, the auto-catalytic reduction rate of nitric acid increases, and
Chapter 6 consequently corrosion potential rises in the noble direction. Nevertheless, the rise of OCP in the noble direction for TiO 2 coated specimens in both the test solutions is attributed to good passive film property [22]. 6.2.2.3 Electrochemical impedance analysis The electrochemical impedance analysis of the uncoated and TiO 2 coated 304L SS specimens in OCP condition are shown in Fig. 6.10a-d. The Bode plots (Log |Z| vs. Log f and vs. Log f) clearly showed improved protection for TiO 2 coated specimens in both the test solution compared to base material as well as Ti coated specimens. The plot of phase angle (), and frequency in 1 M nitric acid showed one time constant feature as compared to two time constant feature for Ti coated specimens with near capacitive property over a wide frequency indicating greater passive film stability, and resistance to anodic activity (Fig. 6.10a). Fig. 6.10a: Log f vs. for uncoated and TiO 2 coated 304L SS in 1 M HNO 3 [22].
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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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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
Page 102 and 103: Chapter 4 The surface morphologies
Page 104 and 105: Chapter 4 a b c d Opening up of gra
Page 106 and 107: Chapter 4 Intensity (Arbitrary unit
Page 108 and 109: Chapter 4 The chromium, and oxygen
Page 110 and 111: Chapter 4 Intensity (Arbitrary unit
Page 112 and 113: C H A P T E R5
Page 114 and 115: Chapter 5 elements, and often impar
Page 116 and 117: Chapter 5 5.2 Results and discussi
Page 118 and 119: Chapter 5 Presence of oxygen is due
Page 120 and 121: Chapter 5 was an increase in marten
Page 122 and 123: Chapter 5 formation of Cr 2 N was a
Page 124 and 125: Chapter 5 electrochemical environme
Page 126 and 127: Chapter 5 N + Dose E corr (mV vs. A
Page 128 and 129: Chapter 5 layer capacitance (C dl )
Page 130 and 131: Chapter 5 correlation between surfa
Page 132 and 133: Chapter 5 boundary dissolution was
Page 134 and 135: Chapter 6 C H A P T E R 6
Page 136 and 137: Chapter 6 193]. As a single phase c
Page 138 and 139: Chapter 6 particles range from 8×1
Page 140 and 141: Chapter 6 Results revealed that in
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 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
Page 164 and 165: Chapter 6 6.2.3.2 Open circuit pote
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 178 and 179: Chapter 7 6 Duplex Ti-TiO 2 coated
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
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[139] V. Ashworth, R. P. M. Procter
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[176] G. Frankel, G. Grundmeier, H.
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List of publications 1. Referred
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CHEM02200704003 Nilamadhab Pandhy - Homi Bhabha National ...

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