Effect of Alloying Tin on the Corrosion Characteristics of Austenitic Stainless Steel in Sulfuric Acid and Sodium Chloride Solutions

The effect of tin on general and pitting corrosion behaviors of the austenitic stainless steel in sulfuric acid and sodium chloride solutions was investigated by potentiostatic critical pitting temperature, cyclic potentiodynamic polarization, electrochemical impedance spectroscopy, and scanning electron microscopy. The results showed that there is an optimal tin addition which is around (0.062–0.1) wt%, and the general corrosion resistance of B316LX with 0.08 wt% tin addition in boiling H2SO4 increased remarkably with a corrosion rate of an order of magnitude lower than that of 316L. Hydrolyzation of tin ions induces more metastable pit occurrence on the material surface. However, the pitting resistance of B316LX increases because tin oxides improve the density and uniformity of the passive film, and hydroxide and oxide of tin inhabit the process of pit growing. The effect of tin on pitting corrosion process is illustrated schematically.