Corrosion kinetics of pure metals (Fe, Cr, Ni) and alloys (A709, SS316) in thermal and chemical purified molten chloride salt

Abstract

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.