Abstract
Electrochemical short circuiting" describes the loss in current efficiency (CE) due to polyvalent impurity elements that are reduced at the cathode and re-oxidized at the anode. In aluminium cells; the oxidized form of the impurity reacts with dissolved metal near the metal-electrolyte interface, leading to a steeper concentration gradient of dissolved metal. The phenomenon was studied in a model based on the Stefan-Maxwell equations for diffusion in multi component systems and a description of the turbulent diffusion coefficient close to the cathode. The results indicate that the main factors for the slope of CE vs. impurity concentration are the CE in absence of impurities and the change in oxidation state during the reduction, while the diffusion coefficient of the impurity is of minor importance. The numerical results could be represented by an analytical expression that fits well with experimental data.
