Role of thiosulfate in susceptibility of AISI 316L austenitic stainless steels to pitting corrosion in 3.5% sodium chloride solutions

Abstract

The susceptibility of AISI (American iron and steel institute) 316L austenitic stainless steel alloy to pitting corrosion was assessed in 3.5% chloride solutions containing various concentration of thiosulfate ions, a main sulfide oxidant product, spanning across values of 0.001, 0.005, 0.01, 0.05 and 0.1 M, at temperatures of 23, 50 and 80°C. The potentiodynamic scan results indicated that low thiosulfate concentrations promote the chloride attack and the aggressiveness of thiosulfate species depends on the chloride to thiosulfate ratio and the test temperature. Increasing temperature apparently promotes the ionic activity of Cl^– and S₂O₃^2– The thiosulfate to chloride ratio plays an essential role in pitting the intensity of the AISI 316L stainless steel alloy and was found to be dependent on the test temperature.