Influences of heat treatment on the oxidation and corrosion behavior of Cu–Ni–Fe inert anodes for aluminium electrolysis

Abstract

Abstract The homogenization heat-treatments were implemented to the experimental as-cast Cux(Ni1.67Fe)100-x alloys with x = 60,52,44 wt%, which have a two-phase structure to obtain a uniform microstructure. Moreover, the oxidation kinetics of the as-cast and as-homogenized Cux(Ni1.67Fe)100-x alloys were investigated by the thermogravimetry at 850 °C under 1atm O2 atmosphere. The thermogravimetry results showed that all the samples approximately follow the parabolic law during oxidation under this condition. The homogeneous alloys have the lower oxidation rate than the as-cast alloys due to the inhibition of outward diffusion of Cu. Furthermore, the as-cast and as-homogenized 52Cu–30Ni–18Fe alloys were tested as inert anode materials in laboratory aluminium electrolysis tests. The as-homogenized 52Cu–30Ni–18Fe alloy anode performs significantly better corrosion resistance due to the formation of NiFe2O4. In the end, there is less impurity contents of Cu in the produced aluminium after electrolysis using the as-homogenized 52Cu–30Ni–18Fe alloy anode than using the as-cast 52Cu–30Ni–18Fe anode.