Effect of Chloride Ion Impurities on Corrosion Behavior of 304 and 316L Austenitic Stainless Steel in Molten Nitrate Salt

The corrosion behaviors of 304 and 316L austenitic stainless steel immersed in molten nitrate salt (60% NaNO₃ + 40% KNO₃,mass fraction) with different mass fraction (0,0.6%,1.0%,1.4%) of chloride ion impurity at 565℃ were studied using constant temperature immersion corrosion test method. The results show that 304 and 316L stainless steel in four types of molten nitrate salts exhibited parabolic corrosion kinetic. With increasing chloride content, the corrosion rate of 304 and 316L stainless steel increased significantly, the corrosion degree gradually increased, and the cracks of the corrosion product layer at the junction with the substrate increased. Chloride ion impurities accelerated the corrosion of stainless steel through active oxidative corrosion. Compared with 316L stainless steel, 304 stainless steel was more sensitive to the corrosive effect of chloride ion impurities.