Corrosion of 316L stainless steel in Eutectic KCl-LiCl under a Thermal Gradient Using a Natural Circulation Loop

This study investigates the corrosion behavior of 316L stainless steel in KCl-LiCl molten salt using a natural circulation loop. The loop was operated for 144 hours with a maximum temperature of 600°C (hot leg) and a minimum temperature of 450°C (cold leg). At the end of the test, the salt was allowed to solidify within the loop, and the loop was sectioned into small coupons to examine the corrosion behavior at various locations. The salt chemistry was analyzed at corresponding positions to correlate with the observed corrosion damage. Material characterization of extracted coupons revealed distinct corrosion behaviors between the hot and cold legs. In the hot leg, intergranular corrosion was the predominant mechanism, with preferential dissolution of Fe, Cr, and Mn. Additionally, deposition of Cr-rich oxide was observed in the hot leg. In contrast, the cold leg exhibited metallic deposits on the surface. These findings highlight the influence of the temperature gradient and salt chemistry on corrosion processes in molten salts. The underlying corrosion mechanisms are discussed, focusing on the role of thermal gradients and salt composition in modulating corrosion rates and morphology. The results of this work have implications for materials selection and system design in high-temperature molten-salt loops.