Metallic oxygen evolving anode operating at high current density for aluminium reduction cells

摘要

A metallic oxygen evolving anode for electrowinning aluminium by decomposition of alumina dissolved in a cryolite-based molten electrolyte, and operable at anode current densities of 1.1 to 1.3 A/cm2, comprises an alloy of nickel, iron, manganese, optionally copper, and silicon. Preferably, the alloy is composed of 64-66w% Ni; Iron; 25-27w% Fe; 7-9w% Mn; 0-0.7w% Cu; and 0.4-0.6w% Si. The weight ratio Ni/Fe is in the range 2.1 to 2.89, preferably 2.3 to 2.6, the weight ratio Ni/(Ni + Cu) is greater than 0.98, the weight ratio Cu/Ni is less than 0.01, and the weight ratio Mn/Ni is from 0.09 to 0.15. The alloy surface can comprise nickel ferrite produced by pre-oxidation of the alloy. The alloy, optionally with a pre-oxidised surface, can be coated with an external coating comprising cobalt oxide CoO.