Detailed Model of Electrochemical Cathode Wear in Hall-Héroult Cells

Abstract

Clarification of the underlying chemistry and physics is critical for understanding the “double W” wear pattern of the carbon cathode observed in Hall-Heroult cells. Many studies have pointed out that aluminium carbide formation on the cathode surface is the dominating process that determines the cathode wear. However, the mechanisms of aluminium carbide formation on the carbon cathode surface are still not well clarified. In this study, previous work on cathode wear mechanism is summarized. The region between molten aluminium and the carbon cathode is considered as a small “local electrolysis cell” involving the aluminium pad, a bath film, an aluminium carbide layer, and the carbon cathode. The aluminium carbide formation rate is proportional to the current through the “local electrolysis cell” which is obtained by applying Ohm’s law to the current and voltage of the electro-chemical reaction. A model is established for calculating the aluminium carbide formation rate as well as the cathode wear rate.