Impact of salt purification and flow conditions on SS316H corrosion in molten NaF–KF–UF₄

Flow-accelerated corrosion of stainless steel 316H (SS316H) in NaF–KF–UF₄ salt (FUNaK) was investigated using a rotating cylinder system. Corrosion tests were conducted with FUNaK synthesized to contain varying levels of impurities and UF₃ concentrations to evaluate their influence on the corrosion behavior of SS316H. Different salt flow conditions were simulated by adjusting the rotational speed of the SS316H specimens to assess the influence of the flow condition on SS316H corrosion. Corrosion of SS316H in FUNaK with high oxygen concentrations led to the depletion of alloy constituents and salt penetration along grain boundaries, resulting in significant selective dissolution of the constituents into salt. Additionally, corrosion of SS316H was more severe under turbulent flow conditions compared to laminar flow. Within the turbulent flow regime, however, variations in flow condition of salt with high oxygen content showed limited impact on SS316H corrosion, likely due to the dominant influence of oxygen on corrosion and/or the formation of an iron-enriched surface layer.