Cathode Wear Based on Autopsy of a Shutdown Aluminium Electrolysis Cell

To investigate cathode wear, an autopsy of a shutdown aluminium electrolysis cell was conducted. The original lining consisted of a fully impregnated and graphitized carbon block and the cell was shut down after 2461 days operation. The cell was cleaned down to the surface of the carbon cathode, revealing the profile of the cathode wear. Generally, the cathode wear was uneven across the cell with typical potholes. At a finer length scale, the wear was characterized by small “pitholes” resembling wide shallow pitting corrosion. Samples of the cell lining were obtained by drilling cylindrical samples at different locations in the cell. These samples were analysed with respect to phase composition and microstructure by a combination of X-ray computed tomography, optical and electron microscopy. The findings are discussed in relation to the current understanding of the underlying mechanism(s) for cathode wear.