Abstract: A method of manufacturing an anode for use in a cell for the electrowinning of aluminium comprises oxidising before cell operation an iron-nickel alloy substrate in an oxygen-containing atmosphere, such as air, at a temperature which is at least 50° C., preferably 100° C., above the operating temperature of the cell to form on the surface of the iron-nickel substrate a coherent and adherent iron oxide-containing outer layer, in particular a hematite-containing layer having a limited ionic conductivity for oxygen ions and acting as a partial barrier to monoatomic oxygen. The outer layer is electrochemically active for the oxidation of oxygen ions and reduces also diffusion of oxygen to the iron-nickel alloy substrate when the anode is in use.

Abstract: A cell for the electrowinning of aluminium comprising one or more anodes (10), each having a metal-based anode substrate, for instance comprising a metal core (11) covered with an metal layer 12, an oxygen barrier layer (13), one or more intermediate layers (14; 14A, 14B) and an iron layer (15). The anode substrate is covered with an electrochemically active transition metal oxide layer, in particular an iron oxide-based outside layer (16) such as a hematite-based layer, which remains dimensionally stable during operation in a cell by maintaining in the electrolyte a sufficient concentration of iron species and dissolved alumina. The cell operating temperature is sufficiently low so species and dissolved alumina.

Abstract: Carbon-containing components of cells for the production of aluminium by the electrolysis of alumina dissolved in a cryolite-based molten electrolyte are protected from attack by liquid and/or gaseous components of the electrolyte in the form of elements, ions or compounds, by a refractory boride coating applied from a slurry composed of pre-formed particulate refractory boride in a colloidal carrier which is dried and heated to consolidate the coating.

Abstract: 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.

Abstract: A bipolar cell for the electrowinning of aluminum has bipolar electrodes each comprising a carbon cathode body having on one side an active surface on which aluminum is produced and connected on the other side through an oxygen impermeable barrier layer to an electrochemically active anode layer having an oxygen evolving iron oxide-based outer surface. The anode layer may comprise a metal-based anode substrate and a transition metal oxide-based outside layer, in particular an iron oxide-based outside layer, which either is an applied layer or is obtainable by oxidising the surface of the anode substrate which contains iron. During operation, the anode layer can be kept dimensionally stable by maintaining in the electrolyte a concentration of transition metal species which are present as one or more corresponding transition metal oxides in the electrochemically-active layer.

Abstract: A non-carbon, metal based slow-consumable anode of a cell for the electrowinning of aluminum self-forms during normal electrolysis an electrochemically-active oxide-based surface layer (20). The rate of formation (35) of the layer (20) is substantially equal to its rate of dissolution (30) at the surface layer/electrolyte interface (25) thereby maintaining its thickness substantially constant, forming a limited barrier controlling the oxidation rate (35). The anode (10) usually comprises an alloy or iron at least one of nickel, copper, cobalt or zinc which during use forms an oxide surface layer (20) mainly containing ferrite.

Abstract: A non-carbon, metal-based slow-consumable anode of a cell for the electrowinning of aluminium self-forms during normal electrolysis an electrochemically-active oxide-based surface layer (20). The rate of formation (35) of the layer (20) is substantially equal to its rate of dissolution (30) at the surface layer/electrolyte interface (25) thereby maintaining its thickness substantially constant, forming a limited barrier controlling the oxidation rate (35). The anode (10) usually comprises an alloy of iron with at least one of nickel, copper, cobalt or zinc which during use forms an oxide surface layer (20) mainly containing ferrite.

Abstract: An electrolytic cell and electrolytic process for producing a metal by reduction of a metal oxide dissolved in a molten salt bath containing at least one chloride and at least one fluoride. A solid conductor of oxide ions is interposed between the anode and the cathode. The solid conductor preferably comprises zirconia, stabilized in cubic form by addition of a divalent or trivalent metal oxide such as yttria.

Abstract: A non-carbon, metal-based anode (10) of a cell for the electrowinning of aluminium, comprising an electrically conductive, high temperature resistant and oxidation resistant metal structure (11) in the form of a wire mesh or net, a foraminate sheet, a fibrous network, a reticulated skeletal structure, or a porous structure having voids, recesses and/or pores which are filled or partly filled with an electrochemically active filling (12), such as oxides, oxyfluorides, phosphides, carbides, cobaltites and cuprates making the surface of the anode (10) conductive and electrochemically active for the oxidation of oxygen ions present at the anode surface/electrolyte (5) interface.

Abstract: A non-carbon, metal-based high temperature resistant anode of a cell for the production of aluminium has a metal-based substrate coated with one or more electrically conductive adherent applied layers, at least one electrically conductive layer being electrochemically active. The electrochemically active layer contains one or more electrocatalysts fostering the oxidation of oxygen ions as well as fostering the formation of biatomic molecular gaseous oxygen to inhibit ionic and/or monoatomic oxygen attack of the metal-based substrate. The electrocatalyst can be iridium, palladium, platinum, rhodium, ruthenium, silicon, tin, zinc, Mischmetal oxides and metals of the Lanthanide series. The applied layer may further comprise electrochemically active constituents from oxides, oxyfluorides, phosphides, carbides, in particular spinels such as ferrites.

Abstract: A dimensionally stable electrode is provided comprising a hollow substrate with an open upper end for confining a fluid containing a metal, a film covering portions of the external surface; and a mechanism for replenishing the film. Also provided is a method for maintaining the dimensions of an anode during electrolysis comprising adapting an interior surface of the anode to receive a fluid containing a metal, facilitating transport of the metal to an exterior surface of the anode, forming a protective film on the exterior surface, wherein the transported metal is a cation of the formed protective film, and maintaining the protective film on the exterior surface while the anode is in use.

Abstract: A composite, high-temperature resistant, non-carbon metal-based anode of a cell for the electrowinning of aluminium comprises a metal-based core structure of low electrical resistance, for connecting the anode to a positive current supply, coated with a series of superimposed, adherent, electrically conductive layers. These layers consist of at least one layer on the core structure constituting a barrier substantially impervious to monoatomic oxygen and molecular oxygen; one or more intermediate, protective layers on the oxygen barrier layer which remain inactive in the reactions for the evolution of oxygen gas; and an electrochemically active layer for the oxidation reaction of oxygen ions present at the anode/electrolyte interface into nascent monoatomic oxygen, as well as for subsequent reaction for the formation of gaseous biatomic oxygen.

Abstract: Carbon-containing components of cells for the production of aluminium by the electrolysis of alumina dissolved in a cryolite-based molten electrolyte are protected from attack by liquid and/or gaseous components of the electrolyte in the form of elements, ions or compounds, by a refractory boride coating applied from a slurry composed of pre-formed particulate refractory boride in a colloidal carrier which is dried and heated to consolidate the coating.

Abstract: An anode for the electrowinning of aluminium by the electrolysis of alumina dissolved in a molten fluoride electrolyte comprises a porous combustion synthesis product of nickel, aluminium, iron, copper and optional doping elements in the amounts 50-90 wt. % nickel, 3-20 wt. % aluminium, 5-20 wt. % iron, 0-15 wt. % copper and 0-5 wt. % of one or more of chromium, manganese, titanium, molybdenum, cobalt, zirconium, niobium, tantalum, yttrium, cerium, oxygen, boron and nitrogen. The combustion synthesis product contains metallic and intermetallic phases. A composite oxide surface is produced in situ by anodic polarization of the porous combustion synthesis product in a molten fluoride electrolyte containing dissolved alumina. The in situ formed composite oxide surface comprises an iron-rich relatively dense outer portion, and an aluminate-rich relatively porous inner portion.

Abstract: A cell for the production of aluminium by the electrolysis of a molten electrolyte, in particular the electrolysis of alumina dissolved in a molten fluoride-based electrolyte such as cryolite, comprises anodes immersed in the molten electrolyte above a cell bottom whereon molten product aluminium is collected in a pool containing bodies of aluminium-resistant material. Under the anodes are corresponding grids made of side-by-side upright or included walls aluminium-resistant material whose bottom ends stand on a ceramic-coated carbon cell bottom covered by the pool molten aluminium. The bottom ends of the grid walls form a base which is large compared to the height of the walls. Each grid on the cell bottom in stable manner during the operation of the cell and is easily removable from the cell and insertable in the cell.

Abstract: Carbon-containing components (1, 2, 5) of cells for the production of aluminium (8) by the electrolysis of alumina dissolved in a cryolite-based molten electrolyte (7) are protected from attack by liquid and/or gaseous components of the electrolyte (7) in the form of elements, ions or compounds, by a refractory boride coating (9, 10, 11) applied from a slurry composed of preformed particulate refractory boride in a colloidal carrier which is dried and heated to consolidate the coating.

Abstract: A method of reducing the airburning tendency of petroleum coke and carbon anodes made therefrom includes calcining the coke and spray quenching the calcined coke with an additive-containing water. The additive includes an effective amount of a compound of aluminum which is soluble in the quench water. The additive is deposited on the quenched coke product surface and protects the coke from oxidation or premature combustion when in contact with the atmosphere at high temperatures. The additive-coated coke can then be formed into an anode which also has a reduced tendency to airburn during use in a high temperature environment such as an aluminum reduction cell or an electric furnace operation.

Abstract: Components of electrolytic cells for the production of aluminum in particular by the electrolysis of alumina in a molten fluoride electrolyte, made of carbon or other microporous material which remains stable or may be consumed in the cell operating conditions, are conditioned to better resist in the cell operating conditions by impregnating them with colloidal ceria, cerium acetate, silica, alumina, lithia, yttria, thoria, zirconia, magnesia or monoaluminum phosphate containing ionic species of sodium, lithium, potassium, aluminum, calcium or ammonium, followed by drying and heat treatment.

Abstract: Carbon-containing components of cells for the production of aluminum by the electrolysis of alumina dissolved in a cryolite-based molten electrolyte are protected from erosion by non-chemical attack due to movement of liquid and/or gaseous components of the electrolyte, by a refractory boride coating applied from a slurry composed of pre-formed particulate refractory boride in a colloidal carrier which is dried and heated to consolidate the coating.

Abstract: An anode for the electrowinning of aluminium by the electrolysis of alumina dissolved in a molten fluoride electrolyte comprises a porous combustion synthesis product of nickel, aluminium, iron, copper and optional doping elements in the amounts 60-90 wt % nickel, 3-10 wt % aluminium, 5-20 wt % iron, 0-15 wt % copper and 0-5 wt % of one or more of chromium, manganese, titanium, molybdenum, cobalt, zirconium, niobium, yttrium, cerium, oxygen, boron and nitrogen. The combustion synthesis product contains metallic and intermetallic phases. A composite oxide surface is produced in-situ by anodic polarization of the porous combustion synthesis product in a molten fluoride electrolyte containing dissolved alumina. The in-situ formed composite oxide surface comprises an iron-rich relatively dense outer portion, and an aluminate-rich relatively porous inner portion.

Abstract: A method for producing a metal in an electrolysis cell comprising an anode, a carbon cathode, and a chamber containing a metal oxide dissolved in a molten salt bath, said method comprising: coating an outer surface portion of the cathode with a coating composition consisting of a refractory metal, a paint comprising an organic polymeric binder, and aluminum powder, and optionally an organic solvent and an oil; and optionally a boron source; curing the coating composition by heating it to an elevated temperature, producing an aluminum-wettable coating on the cathode outer surface portion; and electrolyzing the metal oxide to a metal bypassing an electric current in the molten salt bath between the anode and the coated cathode.