High-temperature corrosion of Cr-Mo steel in molten LiNO3-NaNO3-KNO3 eutectic salt for thermal energy storage

This study investigated the effects of adding chromium on the high-temperature corrosion behavior of Cr-Mo steels in contact with the molten salt used for thermal energy storage. Corrosion testing was performed by immersing Cr-Mo steels with various chromium contents (0, 2.25, 5, 9, 12 wt% Cr) in static molten LiNO3-NaNO3-KNO3 eutectic salt at 550 °C for 250, 500 and 1000 h under nitrogen cover gas. Our results revealed that the corrosion behavior of the steels was governed by oxidation as well as lithiumization. Weight gains in the various forms of steel were positively correlated to corrosion time but negatively correlated to chromium content. Analysis of the microstructure of the corroded steels revealed an outer LiFeO2 and an inner (Fe,Cr)3O4 layers in the corrosion scales found on the steel. In addition, the thicknesses of the corrosion scales and the descaled weight losses of the steels decreased with an increase in chromium content. Our results confirm that the corrosion resistance of steel exposed to molten salt can be dramatically improved by the addition of chromium (9 wt%).