In-depth corrosion mechanisms of Fe- and Ni-based alloys in molten solar salt with varying extents of chloride and sulfate impurities
C. Oskay, B. Grégoire, T.M. Meißner, B.O. Burek, A. Solimani, M.C. Galetz
Corrosion Science 247 (2025), 112775, DOI: 10.1016/j.corsci.2025.112775
Fig. 5. (a) Cross-sectional BSE image together with an enlarged section of the oxide scale, (b) elemental distribution maps, (c) Na/Fe/O, Cr/O and Cr/N combination maps, and (d,e) concentration profiles of X20 after 1000 h exposure in Salt C. Please note the dashed line showing the Cr concentration in X20 steel.
Fig. 15. (a) Difference of Fe, Ni, Cr and Mn concentrations in Salt C samples after 1000 h immersion of investigated alloys at 600°C from the blank Salt C exposed to same conditions without any metallic sample as baseline (please note the y-axis break), (b) Cr-concentration in Salt C samples determined by ICP-MS, (c) Specific Cr-Loss calculated from the measured Cr-concentration in Salt C samples.Reprinted from Corrosion Science, Copyright (2025), with permission from Elsevier.
Solar salt is currently used in concentrated solar power plants with thermal energy storage. Thermal decomposition of nitrates increases the concentration of oxidizing agents and melt basicity, leading to accelerated corrosion of containment materials. This is further complicated by the impurities in industrial-grade salts. In this study, the corrosion behavior of X20CrMoV12-1, Alloy 800 H, and Haynes-230 is investigated at 600°C in different solar salt mixtures with varying impurity contents. Corrosion mechanisms, including aspects of salt decomposition, impurities, and Cr-dissolution, are discussed in detail. It is proposed that the reactants for oxidation, fluxing, and nitridation are generated from either nitrate or nitrite anions at the alloy/scale interface.
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