Synergistic Effect of S^2- and Cl^- on Corrosion and Passivation Behavior of 316L Austenitic Stainless Steel

The synergistic effect of S^2- and Cl^- on corrosion resistance of 316L austenitic stainless steel in artificial seawater with different S^2- concentrations were studied by using electrochemical testing techniques, SEM, CLSM, EDS, and XPS. The results showed that S^2- and Cl^- have synergistic damaging effects on the corrosion resistance of 316L austenitic stainless steel. S^2- inhibited passivation film generation by competitive adsorption with OH^-, and the participation of S^2- in the passivation process is conductive to the formation of FeS and MoS₂, increasing the doping density but reducing the shielding perfor mance of the passivation film, thus accelerating pitting induced by Cl^-. As the S^2- concentration increased from 0 to 100 mmol/L, the solution pH was increased from 8.2 to 12.8, resulting in a negative shift of the free-corrosion potential E_corr by 0.328 V and an increase in the corrosion current density I_corr approximately one-fold. When the S^2- concentration was greater than 0.1 mmol/L, 316L austenitic stainless steel lost its repassivation performance. When the S²concentration was greater than 100 mmol/L, 316L austenitic stainless steel lost its passivation performance.