Pitting on Carbon Cathodes in Aluminium Electrolysis Cells

Abstract

Uneven cathode wear is one of the key challenges for the lifetime of aluminium electrolysis cells. Here we report on autopsy of several potlinings with focus on the surface morphology of the carbon cathodes. The surface morphology of the spent potlinings was characterized by measuring the profile by a laser interferometer, X-ray computed tomography and microscopy. The surface pitting of the cathodes resembles wide shallow pitting corrosion of metals. The characteristic size of the pittings is determined and compared to the size of the large aggregates constituting the cathode materials. No correlation between the characteristic size of the pitting and the aggregate size is observed. Based on the present findings, aggregate detachment is ruled out as a contributing mechanism to cathode wear.