Electrochemical Behavior of Chromium Difluoride in Molten Lithium and Beryllium Fluoride Mixtures

The interaction between CrF 2 and a molten binary LiF-BeF 2 mixture has been studied using the electrochemical methods. The polarization of the chromium electrode relative to the dynamic beryllium electrode was measured. The obtained voltammetry data elucidates that under the experimental conditions, chromium is observed exclusively in one valence form. According to the cathode polarization dependences, it is established that the reduction of chromium ions in the metal occurs by a two-electron electrode reaction. The equilibrium concentrations of chromium were experimentally measured at the temperatures of 923, 973, and 1023 K at different chromium fluoride concentrations in the melt. The oxidation degree of chromium, dissolved in the melt, was calculated according to the concentration dependences of the equilibrium potentials. A thermodynamic analysis of the chromium difluoride dissolution in a molten mixture of lithium and beryllium fluorides was performed. The formation of dilute solutions of chromium difluoride is accompanied by slight deviations of the salt system from Raoult’s laws. Equilibrium potentials of chromium in the molten LiF-BeF 2 -CrF 2 salt system were measured by the EMF method. Electrode process is realized by a two-electron electrode reaction in the entire range of cathode current densities. Chromium ions in the molten LiF-BeF 2 mixture are predominantly in the divalent state. Reduction of chromium ions proceeds under the diffusion regime. Slight deviations of the LiF-BeF 2 -CrF 2 salt system from the Raoult’s law were observed.