AN ELECTROCHEMICAL CURRENT EFFICIENCY MODEL FOR ALUMINUM ELECTROLYSISCELLS

Previous current efficiency models of the rate of aluminium production in Hall-Heroult cells are briefly summarized. A description and discu ssion of the cathode processes are given, and rate limiting steps are evaluated under the assumption of no concentration gradients in the bu lk electrolyte phase during electrolysis. An electrochemical current e fficiency model is derived from selected rate determining steps. The m odel expresses the local current efficiency in terms of the local part ial current density for the aluminium deposition reaction and the loca l partial current density for all cathodic loss reactions. The model e quations are valid both for laboratory and for commercial cells and in dependent of whether or not electrolyte impurities are involved in cyc lic redox reactions. The necessary precautions to study the parameters affecting current efficiency both in commerical and in laboratory cel ls are outlined.