Corrosion behavior of Ni-Cu alloys in low-temperature KF-AlF3-Al2O3 molten salt for inert anode applications

The corrosion behavior of Ni–Cu alloys with different atomic ratios was systematically investigated in a low-temperature molten salt of 45KF–50AlF 3 –5Al 2 O 3 (wt.%) at 800 °C, to assess their suitability as inert anodes for carbon-free aluminum electrolysis. Pre-oxidation, static corrosion tests, electrochemical measurements, and surface characterization were employed to elucidate composition-dependent corrosion mechanisms and oxide film structure. Under static conditions, Ni-rich alloys form dense NiO-based oxide film with high chemical stability. In contrast, Cu-rich alloys exhibit higher corrosion potentials and lower current densities under electrochemical polarization, indicating superior electrochemical corrosion resistance. During potentiostatic electrolysis, the Ni 50 Cu 50 alloy develops a bilayer oxide structure consisting of an outer Cu 2 O-rich layer and an inner mixed Cu 2 O and NiO layer, which is dense and limits electrolyte penetration. After long-term galvanostatic electrolysis for 493 h, a millimeter-scale multilayer reaction layer forms on the Ni 50 Cu 50 , composed of alternating Cu-enriched and Ni-enriched layers with regions of molten salt infiltration. The growth of this layer drives anode degradation and voltage fluctuations. These results establish a direct correlation between alloy composition, oxide structure, and corrosion performance, revealing the distinct mechanistic governing static chemical dissolution and dynamic electrochemical corrosion. The Ni 50 Cu 50 alloy exhibits both good electrical conductivity and corrosion resistance, the corrosion rate of the Ni 50 Cu 50 alloy is 31.6 mm·a -1 , which provides an important reference for the material selection, design, and performance optimization of multi-component alloy anodes and cermet inert anodes in the aluminum electrolysis industry.