The Aluminum Electrode in AlCl[sub 3]-Alkali-Halide Melts

Abstract

Passivation phenomena have been observed upon cathodic and anodic polarization of the AI electrode in AlCl3-KCI-NaCI melts between 100° and 160°C. They are caused by formation of a solid salt layer at the electrode surface resulting from concentration changes upon current flow. The anodic limiting currents increased with temperature and with decreasing AICI3 content of the melt. Current voltage curves obtained on a rotating aluminum disk showed a linear relationship between the anodic limiting current and u-1/2. Upon cathodic polarization, dendrite formation occurs at the Al electrode. The activation overvoltage in AlCl3-KCI-NaCI (57.5-12.5-20 mole per cent [m/o]) was determined by galvanostatic current step methods. An apparent exchange current density of 270 mA/cm2 at 130°C and a double layer capacity of 40 - 10 μF/cm2 were measured. © 1972, The Electrochemical Society, Inc. All rights reserved.