Abstract: A method of electrowinning a metal by electrolysis of a melt containing a dissolved species of the metal to be won using a non-consumable anode having a metal, alloy or cermet substrate and an operative anode surface which is a protective surface coating of cerium oxyfluoride preserved by maintaining in the melt a suitable concentration of cerium, is characterized by using an anode provided with an electronically conductive oxygen barrier on the surface of the metal, alloy or cermet substrate. The barrier layer may be a chromium oxide film on a chromium-containing alloy substrate. Preferably the barrier layer carries a ceramic oxide layer, e.g. of stabilized copper oxide which acts as anchorage for the cerium oxyfluoride.

Abstract: A ceramic/metal composite material comprises a surface ceramic coating comprising an oxidized alloy of copper stabilized by being in solid solution with nickel oxide or manganese oxide on a substrate which is an oxidation resistant alloy essentially devoid of copper or any metal which oxidizes more readily than copper. The composite is made by oxidizing a copper-based alloy on a substrate and simultaneously oxidizing the substrate surface to form an oxygen-barrier interface, for example a chromium oxide layer formed on an alloy of chrominum with nickel, iron and/or cobalt. The composite may be used as anode substrate for a cerium oxyfluoride coating used in aluminum electrowinning.

Abstract: A non-consumable anode of the type comprising an oxide ceramic coating on a metal substrate, for molten salt electrolysis, namely the electrowinning of metals such as aluminum, has an electronically-conductive oxygen barrier layer between the oxide ceramic coating and the substrate, the oxygen barrier layer containing chromium oxide. Usually, the oxygen barrier layer is a surface film integral with a chromium-containing alloy substrate, comprising 10 to 30% by weight of chromium, 55 to 90% of nickel, cobalt and/or iron and up to 15% of aluminum, titanium, zirconium, yttrium, hafnium or niobium. The ceramic oxide coating may comprise copper oxide in solid solution with at least one further oxide; nickel ferrite; copper oxide and nickel ferrite; doped, non-stoichiometric or partially substituted spinels; or rare earth metal oxides or oxyfluorides.