Experimental Investigation of the Impact

The presence of resistive sludge on the cathode surface in Hall–Héroult cells can increase aluminum production costs and reduce cell lifetime. This study aims to investigate the impact of different cathode grades on sludge formation at the aluminum-cathode interface. A series of five graphitized industrial cathode grades with varying properties were subjected to bench-scale aluminum electrolysis at a current density of 0.9 A/cm², under a nitrogen atmosphere at 1233 K for 8 hours, with a specified initial bath composition. Postmortem analysis involved Rietveld refinement, optical microscopy, and SEM-EDS to characterize the deposits formed during the experiments. Results indicated that sludge accumulation persisted near the center of the cathode surface despite the absence of point feeding, with variability observed among the different cathode grades. Further analysis suggested that sludge formation correlates with the thermal conductivities of the cathode blocks. This investigation enhances the understanding of sludge formation and dissolution mechanisms as they relate to the properties of cathode grades, offering potential pathways for optimizing aluminum production processes.