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CHEM02200704003 Nilamadhab Pandhy - Homi Bhabha National ...

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Chapter 4<br />

4.2 Results and discussion<br />

4.2.1 Ex-situ surface morphology study<br />

The ex-situ results for the immersion study to monitor the surface morphology of passive film<br />

in 1 M, 4 M, 8 M, and 11.5 M nitric acid are presented in Fig. 4.1-4.4. Generally in corrosion<br />

study using AFM, increase in roughness value is considered as increase in corrosion process, and<br />

decrease in roughness value is taken as occurrence of passivation process [121,122]. Figure. 4.1ad<br />

represents the surface morphology of 304L SS in 1 M nitric acid during the immersion up to 27<br />

h.<br />

a<br />

b<br />

c<br />

d<br />

Fig. 4.1: Ex-situ surface morphology of 304L SS in 1 M HNO 3 with increase in immersion<br />

time, (a) As polished, (b) 9 h, (c) 18 h, and (d) 27 h.

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