Electrochemical corrosion and aluminum electrolysis performance of pre-oxidized Fe-Ni alloys in NaF-AlF 3 -NaCl-CaF 2 -Al 2 O 3 molten salt

Abstract The development of inert anodes for aluminum electrolysis offers a promising route to reduce greenhouse gas emissions and improve energy efficiency in metal production. In this study, pre-oxidized Fe–Ni alloys with varying Fe/Ni ratios were systematically investigated as inert anodes in NaF–AlF 3 –CaF 2 –NaCl–Al 2 O 3 molten salt at 880 °C. Linear sweep voltammetry (LSV), 8 h galvanostatic electrolysis, and XRD/SEM-EDS characterizations were used to elucidate how alloy composition regulates anodic polarization, passive film properties, and electrolysis performance. Ni-rich alloys showed multi-stage polarization (active dissolution, passivation, reactivation, over-passivation), while Fe-rich alloys exhibited a single oxidation peak. The near-equimolar 43Fe–57Ni alloy formed a NiFe 2 O 4 spinel-dominated passive layer post-pre-oxidation, yielding the highest apparent passivation-region resistance (20.5 Ω) and lowest passivation current. Galvanostatic electrolysis confirmed the 43Fe–57Ni anode retained structural integrity, with minimal Fe/Ni dissolution (0.08 wt% and