Patent ID: 6562224
Filing Date: 2003-05-13
Classification: C25C

Abstract:
A method of manufacturing an anode for use in a cell for the electrowinning of aluminium by the electrolysis of alumina dissolved in a fluoride-containing molten electrolyte at an operating temperature in the range of 700Â° to 970Â° C., the anode comprising an iron-nickel alloy substrate, the method comprising before use in an electrolyte at an operating temperature in said range oxidising the iron-nickel alloy substrate in an oxygen-containing atmosphere at a temperature (hereinafter called the â€œoxidation temperatureâ€ ) which is at least 50Â° C. above said operating temperature to form on the surface of the iron-nickel substrate a coherent and adherent iron oxide-containing outer layer having a limited ionic conductivity for oxygen ions and acting as a partial barrier to monoatomic oxygen, the outer layer being electrochemically active for the oxidation of oxygen ions and reducing also diffusion of oxygen into the iron-nickel alloy substrate when the anode is in use.