Polarization of liquid zinc cathode in chloride-fluoride melts containing beryllium and yttrium ions

The equilibrium potentials of beryllium in chloride-fluoride melts at the fluorine-beryllium ion ratio of 2 and 4 and also with an YCl3 addition at 700 deg C have been measured. The beryllium potentials have been found to be far more negative than in the purely chloride melts. The higher ratios result in the lower equilibrium potentials of beryllium. Additions of YCl3 to the electrolyte leads to the shift of the beryllium potentials to the positive side. Empirical dependences have been established for the equilibrium beryllium potentials with respect to its molar fraction concentration in the melts at 700 deg C. Consideration has been given to the polarization of a liquid zinc cathode in the salt melts containing BeF2 and also with YCl3 and NaF additions. At the lower current densities the isolation of beryllium occurs at more positive potentials as compared with equilibrium potentials. At the permanent concentration of BeF2 in the electrolyte and varying content of yttrium, the cathodic potential increases in proportion to the logarithm of the YCl3 molar fraction concentration. The discharge of the yttrium and beryllium ions is accompanied by a significant depolarization. A change in the beryllium concentration in the electrolyte at the permanent concentration of YCl3 does not produce any noticeable effect on the potentials of the zinc cathode