Patent ID: 7431812

Claim:
An alloy-based anode for the electrowinning of aluminium by the electrolysis of alumina in a molten fluoride electrolyte, having an electrochemically active integral outside oxide layer obtainable by surface oxidation of a metal alloy which consists of: 20 to 60, preferably 35 to 60, weight % nickel; 5 to 15, preferably 6 to 12, weight % copper; 1.5 to 5, preferably 1.5 to 4, weight % aluminium; 0 to 2, preferably 0.2 to 0.5, weight % in total of one or more rare earth metals, in particular yttrium; 0 to 2, usually 0.5 to 1.5, weight % of further elements, in particular manganese, silicon and carbon; and the balance being iron, in an amount 25 to 70, preferably 40 to 60, weight %, and which has a copper/nickel weight ratio in the range of 0.1 to 0.5, preferably 0.2 to 0.3.