Potentiodynamic, impedance measurements were carried out on 304 stainless steel in 0.5N, 1.0, 2.0 and 5.0 N H 2 SO 4 solutions. X-ray photoelectron spectroscopic [XPS] studies carried out on 304 stainless steel in H 2 SO 4 solutions revealed the existence of CrOOH, Cr 2 O 3 , -Fe 2 O 3 , -FeOOH, Mn 2 O 3 , Mn 3 O 4 , MnS, Ni (OH) 2 , Ni 2 O 3 , NiO, sulphides. The passive film found to contain chromium oxide inner layer and the dissolution of iron through it caused the formation of oxides of iron namely -Fe 2 O 3 and -FeOOH. Higher oxides of manganese and nickel are also due to dissolution through the film. Sulphates are reduced to sulphur chemically by the released protons from anodic polarization.
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Natarajan et al. (2009) studied this question.
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