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Abstract

Reactions between ions in LiCl-KCl eutectic melt and lead alloys have been studied kinetically between 370 and 450°C. Diffusion of the reducing ionic species across the salt-phase boundary layer was shown to be the rate controlling step for the reductions of Pb⁺⁺ , Cd⁺⁺ , Ag⁺ and In⁺⁺⁺ by lithium and of Cr⁺⁺⁺ by lead. Values of the salt-phase boundary layer thickness were estimated. Limited solubility of the reduced metal in the molten alloy resulted in metal deposition at the phase boundary during the reductions of Co⁺⁺, Cr⁺⁺⁺and Ti⁺⁺⁺by lithium. An apparent homogeneous reaction in the salt occurred during the reductions of Ni⁺⁺ and Pt⁺⁺ by lithium. The mechanisms have not been established but may involve solubility of either lithium or a Li-Pb intermetallic compound in the salt. The interfacial reactions were primarily electrochemical in nature, and never rate controlling. The diffusion coefficients of a number of ions in LiCl-KCl at 400 C were determined. The values showed that ionic diffusion in this eutectic was influenced primarily by the ionic charge of the diffusing species.