Electrochemical Assessment of Corrosion Behavior of 316 Stainless Steel in Sodium Chlorate Solutions

Abstract Corrosion behavior of 316L stainless steel grade in various chlorate mixtures was tested electrochemically. Following ASTM G 61 standard for conducting cycling potentiodynamic polarization and standard surface preparation, wire coupons were used for experiments. In addition to 316L grade some polarization curves were obtained for 304L stainless steel grade and platinum, to be used as reference points. Influence of chloride, dichromate, perchlorate, hypochlorite, sulfate and hydrogen peroxide at varying pH was studied. The presence of hypochlorite or hydrogen peroxide greatly increases the risk of pitting attack. Hypochlorite is more dangerous because it is more stable; peroxide concentration quickly decreases. Change of pH from 5.4 to 8.4 is a very substantial factor in reducing corrosion. However, even when pH was 8.4 and hypochlorite concentration of 10-20 mg/L remained for about 12 hours, pitting corrosion attack occurred.