Impact of Li addition on the chromium corrosion in LiCl-KCl molten salt induced by impurity water

Due to the presence of impurities, especially water, molten salt exhibits corrosivity to metals. As the most active element in structural materials, the corrosion behavior and corresponding chemical species of chromium significantly affect the corrosion resistance of structural materials. Herein, we synthesized LiCl-KCl eutectic salt containing bound H 2 O and OH - impurities, and further prepared molten LiCl-KCl-Li salt solution by adding metallic lithium. Static immersion of chromium sheets in the molten LiCl-KCl and LiCl-KCl-Li at 600 o C were selected as a model system to explore the Cr corrosion induced by impurity water. The Cr sheet in molten LiCl-KCl exhibits obvious corrosive dissolution. The dissolved Cr was found to exist stably as Cr 2+ ions with the dominant form of Li 2 CrCl 4 complex in liquid LiCl-KCl by using high temperature ultraviolet-visible spectroscopy and X-ray absorption spectroscopy. In contrast, due to the addition of Li, which converts bound H 2 O and OH - into O 2- , the Cr sheet in liquid LiCl-KCl-Li did not display observable corrosion. The results reveal that impurity water in chloride molten-salts plays a crucial triggering role in metal corrosion.