Corrosion Behavior of High-Chromium Alloys in Molten LiCl–KCl Eutectic

Abstract

Pyrochemical reprocessing utilizing a molten LiCl–KCl eutectic medium is regarded as the most promising approach for recovering uranium and transuranic elements from spent metallic nuclear fuels. However, the harsh corrosiveness of molten chloride poses a significant challenge to the durability of structural materials. Herein, we report the corrosion behavior of 304 SS, 316H SS and Inconel 800H in LiCl–KCl eutectic salt at 550 °C for 100 h under an argon atmosphere. Experimental results indicate that all three materials can form a rather continuous Cr₂O₃-based scale through oxidation reaction at the beginning, but only the scale developed on 800H maintains excellent protection against corrosion throughout the entire exposure period. In contrast, both 304 SS and 316H SS experience considerable active dissolution on the bare substrate under a detached scale. We suggest that the primary reasons for the outstanding resistance of 800H to molten salt corrosion are the high concentration of noble Ni in the system, which lowers the inclination for active dissolution, and the beneficial addition of Al, which accelerates the formation of a less defective Cr₂O₃-based scale. Our work offers an in-depth understanding on the corrosion performance of high-Cr alloys in molten chloride, insights critical for the selection and subsequent development of structural materials for pyrochemical reprocessing applications.