Electrochemical investigations of pitting corrosion behaviour of type UNS S31603 stainless steel in thiosulfate-chloride environment

The pitting corrosion behaviour of type UNS S31603 stainless steel (316L SS) in 0.01, 0.05 and 0.1 M thiosulfate ion (S₂O₃^2–) in the absence and presence of various concentrations of chloride ion (Cl^–) was studied using the cyclic potentiodynamic polarization method. The influence of major factors which affect pitting corrosion such as pH and temperature, were also investigated. It was found that both the pitting potential (E_pit) and the repassivation potential (E_rp) decreased with increase in Cl^– concentration and solution temperature and a more pronounced difference in E_pit values for various concentrations of S₂O₃^2– in 1.0 M Cl^– was obtained at lower temperatures. The effect of pH on E_pit, E_corr and E_rp values for different concentrations of S₂O₃^2– in the presence of 1.0 M Cl^– was also determined.