Recently, the Molten Salt Corrosion team of Shanghai Institute of Applied Physics, Chinese Academy of Sciences has made an important progress in the study of corrosion behaviors of metallic materials in fluoride and chloride salts. They contribute a lot to the success in decreasing the corrosion of metallic materials.

The Molten Salt Corrosion team developed a series of loops to study the corrosion of metallic materials in molten salts. The LiF-BeF₂ thermal convection loop has been successfully operating for more than two years. The long-term corrosion behavior of Nickel-based alloys and stainless steels were carried out in this loop. The corrosion mechanisms of metallic materials, the effect of graphite and leakage on the corrosion of metallic materials, as well as the method to decrease the corrosivity of molten salts were systematically investigated.

Researchers in this team find that impurities in molten salts can drive the corrosion of metallic materials. Usually, the corrosion of metallic materials at the hot section is severer than that at the cold one. The corrosion products usually transfer to the cold section and deposit. For example, the BeCr₂O₄ was detected on the surface of alloy after corroded at the cold section of LiF-BeF₂ thermal convection loop. They also found that the air leakage into loops can continuously drive the corrosion of metallic materials in the molten salts. Therefore, the methods to decrease the corrosion of metallic materials in molten salts were investigated. One method is to decrease the corrosivity of molten salts by reducing the concentration of impurities in salts. It is verified that the corrosion of metallic materials can be obviously reduced by this method. And no obvious corrosion  was observed in the metallic materials after immersion in LiF-BeF2, LiF-NaF-KF, and NaCl-KCl-MgCl2 salt for ≥1000 h, as shown in Fig. 1.

The results were published in Corrosion Science entitled “Corrosion behavior of GH3535 alloy in molten LiF-BeF2 salt”. Prof. Xinmei Yang is the first author. Huajian Liu, Bingchuan Chen, and Xinmei Yang are the corresponding authors. This work was supported by the National Natural Science Foundation of China, the “Transformational Technologies for Clean Energy and Demonstration”, Strategic Priority Research Program of Chinese Academy of Sciences, and the Strategic Priority Research Program of the Chinese Academy of Science.

Fig. 1 Cross-sectional SEM image of the corroded metallic materials

(a) the 316H SS after corrosion in the impure NaCl-KCl-MgCl2 salt for 100 h; (b) the 316HSS after corrosion in the NaCl-KCl-MgCl2 salt (with corrosion control) for 3000 h;(c) the GH3535 alloy after corrosion at the hot section; (d) that after corrosion at the cold section in the LiF-BeF2 thermal convection loop (with corrosion control) for 1000 h; (e) the GH3535 alloy after corrosion at the hot section;(f) that after corrosion at the cold section in the LiF-NaF-KF thermal convection loop (with corrosion control) for 5000 h.

Article Link：https://doi.org/10.1016/j.corsci.2022.110168