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CHEM02200704003 Nilamadhab Pandhy - Homi Bhabha National ...

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Chapter 6<br />

of the passive film at the coating-substrate interface as compared to uncoated condition. However,<br />

as observed in case of Ti coated specimens, the circuit parameters mentioned in Table. 6.3, such as<br />

coating capacitance, and pore resistance showed decreasing trend from 1 M to 8 M nitric acid.<br />

Similar trend was also observed for polarization resistance and double layer capacitance even<br />

though values are superior to Ti coated condition.<br />

6.2.2.4 Potentiodynamic polarization study<br />

The potentiodynamic polarization study carried out in 1 M and 8 M nitric acid for uncoated<br />

and TiO 2 coated 304L SS specimens are shown in Fig. 6.11a-b. The polarization parameters<br />

evaluated for the uncoated, and TiO 2 coated 304L SS specimens are shown in Table. 6.4. It is clear<br />

that, passive current density (I pass ) and corrosion current density (I corr ) decreased, and transpassive<br />

potential (E transpass ) increased for TiO 2 coated specimens compared to uncoated specimens<br />

indicating beneficial effects of titanium dioxide in nitric acid medium [22].<br />

Fig. 6.11a: Polarization study of uncoated and TiO 2 coated 304L SS in 1 M HNO 3 [22].

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