Interaction of MgO Recyclate‐Based Cermet Anode With KF‐AlF ₃ ‐Al ₂ O ₃ at 800°C During Laboratory Scale Aluminum Molten Salt Electrolysis

Upcycling end‐of‐life MgO–C refractories into functional anodes offers a sustainable pathway toward carbon‐free aluminum electrolysis. Here, a metal‐ceramic composite anode was manufactured from refractory‐recyclate‐derived MgO powder and 316L stainless steel by cold isostatic pressing and sintering. It was evaluated in laboratory‐scale molten‐salt electrolysis using potassium cryolite (KF–AlF 3 –Al 2 O 3 ) at 800°C. Post‐electrolysis SEM–EDX, elemental mapping, Raman spectroscopy and ICP–OES were applied to quantify reaction‐layer formation, electrolyte infiltration and element release into the electrolyte. Multi‐layered reaction zone formed at the anode edge, with hematite ( α ‐Fe 2 O 3 ) as the dominant outer oxide and inward regions containing Mg–F–O oxyfluoride‐related products and Ni–Cr–O phases. Electrolyte infiltration through open porosity reached 3.59 mm, whereas near‐surface corrosion depth was limited to 0.27 mm. MgO depletion was most pronounced within a thin outer oxide‐rich zone, which potentially acted as partial diffusion barrier. Dissolution of anode components into the electrolyte remained below the analytical detection limit (<0.01 wt.%). Cell voltage increased gradually and then rose sharply after ∼50 min, prompting termination at 60 min, consistent with electrolyte evaporation and anode passivation. The results establish a benchmark for recyclate‐based anodes in K‐cryolite and guide optimization of electrolyte composition and anode microstructure.