Review of Molten Salt Corrosion in Stainless Steels and Superalloys

In the context of the global energy structure transformation, concentrated solar power (CSP) technology has gained significant attention. Its future trajectory is oriented towards the construction of ultra-high temperature (700–1000 °C) power plants, aiming to enhance thermoelectric conversion efficiency and economic competitiveness. Chloride molten salts, serving as a crucial heat transfer and storage medium in the third-generation CSP system, offer numerous advantages. However, they are highly corrosive to metal materials. This paper provides a comprehensive review of the corrosion behaviors of stainless steels and high-temperature alloys in molten salts. It analyzes the impacts of factors such as temperature and oxygen, and it summarizes various corrosion types, including intergranular corrosion and hot corrosion, along with their underlying mechanisms. Simultaneously, it presents an overview of the types, characteristics, impurity effects, and purification methods of molten salts used for high-temperature heat storage and heat transfer. Moreover, it explores novel technologies such as alternative molten salts, solid particles, gases, liquid metals, and the carbon dioxide Brayton cycle, as well as research directions for improving material performance, like the application of nanoparticles and surface coatings. At present, the corrosion of metal materials in high-temperature molten salts poses a significant bottleneck in the development of CSP. Future research should prioritize the development of commercial alloy materials resistant to chloride molten salt corrosion and conduct in-depth investigations into related influencing factors. This will provide essential support for the advancement of CSP technology.