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AssigneeMoltech Invent S. A.
InventorsJean-Jacques Duruz, Vittorio de Nora, Olivier Crottaz
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An anode of a cell for the electrowinning of aluminum comprises an iron-nickel alloy body or layer whose surface is oxidized to form a coherent and adherent outer iron oxide-based layer, in particular hematite, the surface of which is electrochemically active for the oxidation of oxygen ions and which reduces diffusion of oxygen from the electrochemically active surface into the iron-nickel alloy body or layer. The anode may be kept dimensionally stable during cell operation by maintaining a sufficient amount of dissolved alumina and iron species in the electrolyte to prevent dissolution of the outer oxide layer of the or each anode and by reducing the electrolyte operating temperature to limit dissolution of iron and by reducing the electrolyte operating temperature to limit dissolution of iron species in the electrolyte.
An anode of a cell for the electrowinning of aluminium by the electrolysis of alumina dissolved in a fluoride-containing molten electrolyte, said anode comprising an iron-nickel alloy body or layer whose surface is oxidised to form a coherent and adherent outer iron oxide-based layer, in particular a hematite-based layer, the surface of which is electrochemically active for the oxidation of oxygen ions and which reduces diffusion of oxygen from the electrochemically active surface into the iron-nickel alloy body or layer.
An anode of a cell for the electrowinning of aluminium by the electrolysis of alumina dissolved in a molten fluoride-containing electrolyte, the anode comprising a nickel-iron alloy-containing body or layer, an electrochemically-active iron oxide-based outside layer, in particular a hematite layer, and a nickel-ferrite selective membrane between the iron oxide-containing outside layer and the nickel-iron alloy-containing body or layer, the nickel-ferrite selective membrane preventing oxidation of the nickel-iron alloy-containing body or layer but permitting migration of iron metal from the nickel-iron alloy-containing body or layer to the iron oxide-containing outside layer where the migrated iron metal is oxidised to form iron- oxide, the nickel-ferrite selective membrane being formed by surface oxidation of the nickel-iron alloy-containing body or layer.
A cell for the electrowinning of aluminium by the electrolysis of alumina dissolved in a fluoride-containing molten electrolyte comprising at least one anode having a iron-nickel alloy body or layer and an outer iron oxide-based layer whose surface is electrochemically active and which reduces diffusion of oxygen from the electrochemically active surface into the iron-nickel alloy body or layer.
The method of claim- 45, comprising adjusting the electrical current supplied to the sacrificial electrode so that it corresponds to a current necessary for the dissolution of the required amount of iron species into the electrolyte replacing the iron which is cathodically reduced and not otherwise compensated.
Dependencies are inferred from the claim text.