CHEM02200704003 Nilamadhab Pandhy - Homi Bhabha National ...

Chapter 6
6.2.2.5 Morphological investigation after potentiodynamic polarization study
The surface morphology of the polarized specimens of uncoated and TiO 2 coated 304L SS
specimens examined using AFM after potentiodynamic polarization in both the concentration of
nitric acid are shown in Fig. 6.12a-d [22]. The morphology of uncoated 304L SS specimens
revealed grain boundary structures in both the test solutions after polarization which is due to
intergranular corrosion in nitric acid medium (Fig. 6.12a and c). The severity of attack was higher
for higher concentration of nitric acid. At higher concentration depletion of protective Cr 2 O 3 film
from the surface occurs due to increase in oxidizing power of nitric acid, which exposes high
energy regions such as grain boundaries to the electrochemical environment [22].
Fig.
6.12a-d: Surface morphology of uncoated and TiO 2 coated 304L SS after potentiodynamic
polarization; (a) uncoated (1 M HNO 3 ), (b) TiO 2 coated 304L SS (1 M HNO 3 ), (c) uncoated (8 M
HNO 3 ), (d) TiO 2 coated 304L SS (8 M HNO 3 ) [22].