Electrochemical Corrosion Study on Nickel and Chromium with Different Surface Orientations in Molten MgCl₂-KCl

In the present work, the electrochemical corrosion tests were performed on single-crystal nickel and chromium with different surface orientations having (100), (110), and (111) facets, in a MgCl2-KCl eutectic molten salt at 500oC under an argon atmosphere. The corrosion rate of Ni is lower than that of Cr, indicating that Ni is electrochemically more stable than Cr in the molten salt. The anodic corrosion rates of different single crystals increase in the order of (111) < (100) < (110). This observation shows that the degree of electrochemical stability is related to the coordination of surface atoms and lower density surfaces yield higher corrosion rates. In addition, the corrosion rate of a polycrystalline sample is similar to that of the single-crystal (110) sample, which suggests that the corrosion rate of the polycrystalline surface is dominated by the orientation with the lowest surface density. This work was supported as part of the Molten Salts in Extreme Environments Energy Frontier Research Center, funded by the U.S. Department of Energy, Office of Science. Keywords: Tafel, Nickel, Chromium, MgCl2-KCl, Single crystal.