Effect of Temperature on the Solubility of Metallic Magnesium in Molten MgCl2-KCl-NaCl

Solubility experiments for magnesium metal in molten MgCl2-KCl-NaCl were run at 500 degrees C, 600 degrees C, and 650 degrees C. This study is relevant for understanding how to control corrosivity of the salt when used for high-temperature heat transfer and storage in systems such as concentrating solar power plants and advanced nuclear reactors. Metal dissolution is a viable option for reducing the redox potential of the salt, which should reduce the rate of corrosion of contacting structural metal alloys. Concentration of metallic magnesium in the salt mixture was determined via measurement of the volume of H-2 generated during dissolution of salt samples in water. Open circuit potential between a W working electrode and Ag|AgCl reference electrode was used to determine when equilibrium had been achieved. The dissolved Mg metal concentration was found to vary between 0.32 wt.% and 0.58 wt.% by hydrogen collection, which was confirmed by measurement of Mg rod mass loss.