Abstract: 5Ni-xNiO-NiFe₂O₄ cermets with different NiO contents were prepared and the corrosion behaviour in Na₃AlF₆-Al₂O₃ melts was investigated in laboratory electrolysis tests. The results indicate that adding NiO is un-favorable to the densification of NiFe₂O₄-xNiO ceramics, while small Ni doping can greatly improve the sintering property. The electrolysis tests show that excess NiO is beneficial to the reduction of Fe while has little effects on that of Ni in the bath; the steady-state concentrations of Ni, Fe are below the corresponding solubilities of NiFe₂O₄-xNiO, implying that corrosion mechanism changes while electrifying. Post-electrolysis examination of anodes shows that Ni metal leaches at the anode surface, yet the substrate ceramic prevents the penetration of bath and the further loss of metal phase.

Key words:  NiFe₂O₄; cermet; corrosion behavior; inert anode; aluminum electrolysis