Wetting of Carbon Cathodes by Molten Electrolyte and Aluminium

The extent to which the carbon cathode is wetted by molten electrolyte or molten aluminium metal is important for understanding the cathode wear during aluminium electrolysis. The present paper reports on a laboratory study of the wettability of four different carbon materials using the immersion–emersion technique. The effect of polarization of the carbon cathode on the wettability was also included in the study. The measurements demonstrated that the carbon material is poorly wetted by the molten electrolyte or the metal. After polarization of the carbon in the cathodic direction, the cathode became quickly wetted by the molten electrolyte. The presence of aluminium during the experiments resulted in enhanced wettability by the molten electrolyte. The carbon materials were analyzed by microscopy after the experiments and formation of Al4C3 was observed on the surfaces of the materials. The role of sodium in relation to enhanced wettability by molten electrolyte is discussed.