Acceleration of thermal decomposition of molten nitrates by Cr in steel and promotion of this effect by halogens

Abstract Molten salts have been widely studied as the most common heat storage medium for concentrated solar power (CSP) plants. However, most studies have focused on the corrosiveness of molten salts, while this study innovatively reveals the role of stainless steel in promoting the decomposition of molten salts and the mechanism by which the halogen ions accelerate this process. Considering commercial Solar Salt as an example, the thermal stability, composition, and thermophysical properties of Solar Salt adding Cl − , Br − , and I − after contacting different stainless steel were analyzed. The results showed that Cr was the main reason for the decomposition of the molten salt, and Cl − , Br − , and I − , all accelerated the decomposition. Meanwhile, different halogen ions promoted the decomposition of molten salts through different mechanisms: oxide layer destruction and chain oxidation.