Microstructure and electrolysis behavior of self-healing Cu–Ni–Fe composite inert anodes for aluminum electrowinning

The microstructure evolution and electrolysis behavior of (Cu52Ni30Fe18)–xNiFe2O4 (x = 40wt%, 50wt%, 60wt%, and 70wt%) composite inert anodes for aluminum electrowinning were studied. NiFe2O4 was synthesized by solid-state reaction at 950°C. The dense anode blocks were prepared by ball-milling followed by sintering under a N2 atmosphere. The phase evolution of the anodes after sintering was determined by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results indicate that a substitution reaction between Fe in the alloy phase and Ni in the oxide phase occurs during the sintering process. The samples were also examined as inert anodes for aluminum electrowinning in the low-temperature KF–NaF–AlF3 molten electrolyte for 24 h. The cell voltage during electrolysis and the corrosion scale on the anodes were analyzed. The results confirm that the scale has a self-repairing function because of the synergistic reaction between the alloy phase with Fe added and the oxide phase. The estimated wear rate of the (Cu52Ni30Fe18)–50NiFe2O4 composite anode is 2.02 cm·a−1.