Effect of SO42− on the corrosion of 316L stainless steel in molten FLiNaK salt

The effect of SO42− on the corrosion behavior of 316 L stainless steel (SS) in molten FLiNaK (LiF-NaF-KF: 46.5-11.5-42 mol.%) salt was studied. Results reveal that the SO42− in the salt remarkably accelerates the corrosion of 316 L SS by promoting the dissolution of Cr, leading to increasing intergranular corrosion of the alloy. On the other hand, the results of structural characterization indicate that the SO42− can react with Mn to form MnS at the grain boundaries of the alloy. The galvanic couple between MnS and steel matrix could further accelerate the intergranular corrosion of 316 L SS in molten fluoride salt environments.