Chronopotentiometric Investigation of the Oxidation of Aluminum in Chloroaluminate Melts

Abstract

Oxidation of an aluminum electrode in molten A1Cls-MC1 (63-37 mole per cent, M = Na or Li) has been investigated by chronopotentiometry. Wel l-defined and reproducible transit ion times, caused by the formation of a poorly conducting A]2C16 layer at the electrode surface and the depletion of cur-rent-carry ing alkal i metal ions, were observed. The observations are in very good agreement with the theoretical predictions imilar to those of Braunstein and co-workers. In the range of current densities employed (up to 300 mA/cm 2 at 140 ~ the aluminum electrode behaves reversibly. It has been very recently shown by Braunstein and co-workers (1) that in molten alkal i metal f luoride-beryl l ium fluoride mixtures, the chronopotentiometric oxidation of a beryl l ium anode results in a layer of near ly pure, almost nonconductive BeF2 as the mobi le alkal i metal ions are swept away, and, as the result