Corrosion studies of Ni-free austenitic stainless steel in methanol containing H2SO4, HCl and LiCl

The corrosion behaviour of an austenitic stainless steel containing nitrogen with negligible amount of nickel has been investigated in methanol-H2SO4, methanol-HCl, and methanol-LiCl solutions using potentiostatic polarization technique. The cathodic reaction was the hydrogen evolution reaction. Active, passive and transpassive behaviours were observed only at high concentrations of H2SO4 (0.01-1-0 M) in methanol, and passivity was due to the high inherent water content in sulphuric acid. Pitting was also observed on the steel surface. The pitting potential became nobler as the concentration of H2SO4 increased. In 0. 1 and 1.0 M H2SO4, a cathodic loop, characterized by measured negative current in the anodic region, was also observed. In methanol-HCl and methanol-LiCl solutions, the steel dissolved actively and no active-passive transition was observed. The corrosion rate was significantly higher in methanol-HCI solution as compared to methanol-LiCl due to the synergistic effects of acid and chloride ion.