Polarization of Molten Aluminum and Solid Tantalum Cathodes in Aluminum-containing Chloride Melts.

A study was made of the aluminum ion diffusion and concentration coefficients, the limiting discharge current of Al**3** plus ions, and the thickness of the diffusion layer of the electrolyte during the electrolysis of a KCl-NaCl-AlCl//3 melt using either a molten aluminum or a solid tantalum cathode. The higher values obtained for the limiting discharge current in the case of the molten aluminum cathode and the considerable increase in the discharge current with an increase in the aluminum ion concentration are attributed to a decrease in the thickness of the diffusion layer of the electrolyte due to intense motion of the molten aluminum surface and the electrolyte layer adjacent to it, caused by a nonuniform distribution of the current density, the potential, and the interphase surface tension of the cathode.