The effect of cold work by rolling on electrochemical behaviour of Cr-Mn austenitic stainless steel in chloride environment

The effect of cold work (CW) on electrochemical behaviour of Cr-Mn austenitic stainless steel (AISI 202) in 3.5% NaCl solution was studied through microstructure, x-ray diffraction (XRD), Mott-Schottky (M/S) techniques, Potentiodynamic polarization (PDP), and Electrochemical Impedence Spectroscopy (EIS). The XRD spectrum was used to estimate volume fraction of martensite and dislocation density, whereas EIS and PDP plots were used to evaluate electrochemical behaviour. The M/S plots were used to estimate defect densities of passive film. It is found that as the cold work is increased, austenite transform to martensite and dislocation density increases. It is also found that corrosion resistance of the material decreases as the cold work is increased. When cold work is upto 15%, the material shows passivity. At higher cold work the material looses passivity. It is also found that defect density of passivating film is more when Cr-Mn stainless steel is subjected to more cold work. Most importantly, a relationship between dislocation density of the substrate and defect density of the film has been noticed.