CHEM02200704003 Nilamadhab Pandhy - Homi Bhabha National ...

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Chapter 6 Fig.6.16b: Polarization study of uncoated and duplex Ti-TiO 2 coated 304L SS in 8 M HNO 3 . Conc. Substrate condition E corr mV vs Ag/AgCl I pass µA/cm 2 I corr µA/cm 2 E transpass mV vs Ag/AgCl 1 M Uncoated 250 1.1×10 2 10×10 0 1100 1 M Ti-TiO 2 coated 385 7×10 0 3×10 -1 1316 8 M Uncoated 340 1.2×10 3 7×10 1 1025 8 M Ti-TiO 2 coated 582 1×10 2 11×10 0 1119 Table. 6.6: Average value of polarization parameters for uncoated and duplex Ti-TiO 2 coated 304L SS in 1 M and 8 M HNO 3 . The polarization parameters evaluated for uncoated, and Ti-TiO 2 coated 304L SS are shown in Table. 6.6. The improvement in transpassive potential with respect to titanium coating is 170 mV (vs. Ag/AgCl) in 1 M nitric acid, and 68 mV (vs. Ag/AgCl), in 8 M nitric acid, respectively. Similarly as compared to TiO 2 coating, the improvement in transpassive potential was 66 mV (vs. Ag/AgCl) in 1 M nitric acid, and 44 mV (vs. Ag/AgCl) in 8 M nitric acid, respectively. From the improvement in transpassive potential it is clear that, duplex coating
Chapter 6 exhibits wide passive range as compared to both the single layer coating. It is also evident from, Table. 6.2, Table. 6.4, and Table. 6.6 that duplex Ti-TiO 2 coated specimen exhibited lowest I corr value showing highest corrosion resistance out of the three different coatings investigated in the present investigation. The protection efficiency for the duplex Ti-TiO 2 coating calculated using Eq. 13 are 97 % in 1 M nitric acid, and 84 % in 8 M nitric acid, respectively. The low passive current density as well as higher transpassive potential is due to the combination of good passivation property of outer TiO 2 layer as well as reduction in structural heterogeneity by Ti interlayer. For duplex coating the extent of structural heterogeneities has greater role in predicting the corrosion rate. If the porosity is less, the specimen behaves totally as a coating, and pores are passivated if the coating passivates showing good corrosion resistance. Similarly, if significant pores are there, the coating behaves like base material, and it fails to passivate at the pores and other structural inhomogenities regardless of how noble the coating may be. As can be observed from the Fig. 6.2d, Fig. 6.8d, and Fig. 6.13d, significant reduction of pore density in the duplex coating was observed for duplex Ti-TiO 2 coating compared to Ti and TiO 2 single layer coatings which increases the susceptibility to corrosion by increasing the dissolution rate of the base material. Moreover, from morphology and pore size analysis it is evident that the structure of duplex Ti-TiO 2 layer coating is less columnar, more compact and has fewer pinhole with small surface area as compared to Ti and TiO 2 coating which are essential to restrict the solution path to the base material. Hence, the effective isolation of the base material from oxidizing environment leads to low passive current density as well as corrosion current density. Nevertheless, pores and pinholes also can be observed from Fig. 6.13c in the duplex coating. However “repassivation” ability of the passive film in these region is higher because of small surface area and Ti intermediate layer which can oxidize itself to form protective oxide layer [195, 197, 209].
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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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Page 124 and 125: Chapter 5 electrochemical environme
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Page 132 and 133: Chapter 5 boundary dissolution was
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Page 138 and 139: Chapter 6 particles range from 8×1
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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
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 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,
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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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