Nickel-iron anodes for aluminium electrowinning cells

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An anode of a cell for the electrowinning of aluminium has a nickel-iron alloy outer portion which during use is covered with an integral iron-based oxide surface layer. The nickel-iron alloy outer portion comprises one or more rare earth metals that are substantially insoluble in nickel and iron. These rare earth metals are present in the outer portion in an amount which provides during use controlled diffusion of iron from the outer portion to the integral iron-based oxide surface layer. This controlled diffusion of iron is on the one hand sufficiently high to compensate dissolution of iron oxide from the integral iron-based oxide surface layer into the electrolyte thereby avoiding passivation of the anode by oxidation and/or fluorination of nickel of the outer portion which is not protected by iron oxide, and on the other hand sufficiently low to limit the thickness of the integral iron-based oxide surface layer and maintain its coherence and electrolyte imperviousness thereby avoiding internal corrosion of the integral iron-based oxide surface layer by electrolytic dissolution.