There has been notable research interest in utilizing chloride molten salt as both a heat transfer and thermal energy storage medium in nuclear and solar energy systems. However, a significant concern remains regarding the compatibility of structural materials with chloride molten salt. In this study, electrochemical methods were applied to investigate the corrosion kinetics and mechanisms of pure Ni, Fe, Cr, SS316, and A709 in thermally and chemically purified molten MgCl₂–KCl–NaCl salt to explore the underlying corrosion mechanisms. It was found that the corrosion of metals and alloys in the salt was governed by the diffusion of corrosive impurities at temperatures of 600, 650, and 700 °C. The corrosion rates of each metal/alloy were determined using Tafel analysis under impurity diffusion-controlled conditions. The results showed that the corrosion resistance hierarchy for pure metals was Ni > Fe > Cr, while for alloys, SS316 demonstrated superior corrosion resistance compared to A709 within the tested temperature range and conditions.

The purification of salt is indispensable for mitigating the corrosion of structural materials for molten salt reactors or other molten salt applications. This study develops a salt-purification system to synthesize and purify NaF-KF-UF₄ salt (FUNaK) using Ar purging and hydrofluorination of impurities. Chronoamperometry is also used to remove metallic impurities in the hydrofluorinated FUNaK. This purified FUNaK is then used for a static corrosion test of stainless steel 316H (SS316H) to study the effectiveness of salt purification in mitigating its corrosion. For comparison, results from a previous study about the corrosion of SS316H by thermally purified FUNaK are used. FUNaK with UF₃ is also synthesized for a static corrosion test with the same condition to investigate the impact of UF₃ on corrosion. The results show that the corrosion of SS316H is significantly reduced by using the chemically purified FUNaK compared to thermally purified FUNaK.