Aluminum Company of America

Subodh K Das

Perry A Foster, Jr

Richard A Milito

C Norman Cochran

Donald L Kinosz

Gregory J Hildeman

Aaron J Becker

Robert L Coffman

David A Wohleber

Ronald C Schoener

Paul J Boget

Robert M Mazgaj

Charles J Culleiton

Walter W Hill

A low porosity coating comprised of at least two layers of material or composites capable of protecting a metal substrate from the corrosive effects of a chlorine-metal chloride environment at temperature values ranging up to 650.degree. C. The first of the two layers has a coefficient of thermal expansion that lies between the metal of the substrate and that of a metal oxide(s) layer disposed upon the first layer. A layer of metal oxide is disposed on the first layer, the metal oxide having a coefficient of expansion somewhat less than the first layer and a minimum solubility in the chlorine-chloride environment. The material or composite of the first layer and the metal oxide of the oxide layer are applied by a technique which sprays particles of the material or composite and metal oxide(s) against a surface at relatively high velocities and temperatures.

High temperature, corrosion resistant coating and lead for electrical

An improved electrolytic cell is provided for production of a metal such as aluminum by electrolysis of a compound of the metal in a solvent or bath such as molten salt. Electrolysis is carried out by passing a current from an anode to a cathode between which the solvent bath is situated. The cathode comprises a base cathode and cathode extension surfaces comprising graphite and at least 90% refractory hard metal such as titanium diboride. The cathode extension surfaces are produced from a mixture comprising at least 90% refractory hard metal and a carbonaceous binder with little or substantially no particulate carbonaceous material and graphitizing said mixture above 2350.degree. C. to graphitize the carbonaceous material therein to exhibit the graphitic structure.

Composite cathode

A metal such as aluminum is produced by electrolysis of a compound of the metal in a solvent or bath such as molten salt. Electrolysis is carried out by passing a current from an anode to a cathode between which the solvent bath is situated. The cathode is composed of a composite comprising graphite and a refractory hard metal such as titanium diboride. The properties and performance of the composite cathode are improved through careful manufacturing controls and selectivity with respect to electrode configuration and cell operating conditions.

Electrolytic production of aluminum using a composite cathode

A metal such as aluminum is produced by electrolysis of a compound of the metal in a solvent such as a molten salt. Electrolysis is carried out by passing a current from an anode to a cathode between which the solvent bath is situated. The cathode or cathode member is composed of a graphite substrate coated with a refractory hard metal such as titanium diboride. The coating adhesion of the TiB.sub.2 is improved through control of the manufacture and structure of the graphite substrate to favor a higher coefficient of thermal expansion and to have the density of the graphite fall within a range of 1.6 to 1.85 grams per cubic centimeter. The steps in producing the graphite may include working it so as to provide a grain direction. One embodiment includes aligning the refractory hard metal coated graphite in the electrolytic cell with the graphite grain direction parallel to the direction of current flow from anode to cathode. The refractory hard metal coating can be imparted by chemical vapor deposition and should exhibit a dense columnar structure which reduces penetration of the coating by molten aluminum.

Method of producing aluminum using graphite cathode coated with

In the production of a metal such as aluminum by electrolysis of an electrolyte bath containing a compound of the metal dissolved therein to produce the metal at a graphite cathode surface, the wear rate of the graphite cathode surface is significantly reduced by incorporating therein selected amounts of certain compounds of aluminum or titanium, especially Al.sub.2 O.sub.3 and TiO.sub.2. The improvement is particularly suited to the production of aluminum from chloroaluminate electrolyte baths.

Process for producing aluminum using graphite electrodes having reduced

Chlorination of aluminous materials such as alumina and bauxite is carried out at 575.degree. to 750.degree. C. in the presence of a solid reducing agent. The reducing agent is a green coke which has been calcined at a temperature between 650.degree. C. and 900.degree. C. for a period of from 10 to 120 minutes.

Chlorination of aluminous materials using preselected solid reducing

A carbonaceous electrode for use in a bipolar electrolytic cell is treated on one side with a source of aluminum to form an adherent layer of aluminum carbide thereon. The electrode is arranged in the cell such that on the passage of electrolyzing current the treated surface functions as a cathode. On electrolyzing the cell, chlorine is produced on each anode surface and aluminum is produced on each cathode surface.

Process for producing aluminum and electrodes for bipolar cell

Metal such as aluminum is produced electrolytically from metal chlorides or other halides dissolved in a molten solvent bath of higher decomposition potential in a cell including one or more graphite cathode surfaces spaced from opposed anodes, particularly a bipolar cell, with bath flow through the spaces between the anodes and cathodes. The wetting characteristics of the carbonaceous cathode with respect to the metal deposited there by electrolysis are selectively balanced with the bath flow over the cathode and with the anode-to-cathode distance. Cathode surface wear rate is substantially reduced if the surface is wettable by the metal in regions of low bath flow velocity or regions of greater anode-cathode distance. The wear rate is also reduced by using non-wettable cathode surfaces in regions of higher bath flow velocity or regions of closer anode-cathode distance. Conditions of graphite manufacture, including raw material selection and graphitization temperature, are specified to achieve controlled wettability of graphite electrodes to enable the selective production of either condition for the particular cell operation involved.

Controlled wettability graphite electrodes for selective use in

Metal such as aluminum is produced electrolytically from metal chlorides or other halides dissolved in a molten solvent bath of higher decomposition potential in a cell including one or more carbonaceous or graphite cathode surfaces spaced from opposed anodes, particularly a bipolar cell, with bath flow through the spaces between the anodes and cathodes. The wetting characteristics of the graphite cathode with respect to the metal deposited there by electrolysis are selectively balanced with the bath flow over the cathode and with the anode-to-cathode distance. Cathode surface wear rate is substantially reduced if the surface is wettable by the metal in regions of low bath flow velocity or regions of greater anode-cathode distance. The wear rate is also reduced by using a non-wettable cathode surface in regions of higher bath flow velocity or regions of closer anode-cathode distance.

Selective use of wettable and non-wettable graphite electrodes in

A method is provided for removing aluminum or compounds thereof causing a short circuit in an electrolytic cell containing aluminum chloride dissolved in a molten solvent of higher decomposition potential, the cell used for the production of aluminum from aluminum chloride and having a terminal anode and cathode providing an inter-electrode space therebetween. The method comprises removing aluminum chloride and molten solvent from the cell to an extent which exposes the materials in the inter-electrode space causing the short circuit, introducing a source of chlorinating agent to the cell and contacting the materials causing the short circuit with the chlorinating agent to form aluminum chloride, the contacting being for a time sufficient to remove the short circuit thereby permitting the addition of the aluminum chloride and solvent and the electrolysis thereof for the production of aluminum.

Situ cleaning of electrolytic cells

A process is provided for producing aluminum in an electrolytic cell containing aluminum chloride dissolved in a molten solvent of higher decomposition potential. The cell has a terminal anode, a terminal cathode and a bipolar electrode arranged to operate with the anode and the cathode, providing interelectrode spaces therebetween. On electrolyzing the cell chlorine is produced on each anode surface thereof and aluminum on each cathode surface, the aluminum being swept from the cathode surface by bath material. In the process, carbonaceous material is provided for use as the electrode. The direction of grain flow constituting the carbonaceous material is determined and the electrode is arranged in the cell such that the direction of electrolysis current flow through the cell is in a direction substantially perpendicular to the direction of grain flow in the electrode.

Metal production

A process for purifying aluminum alloys comprises providing molten aluminum alloy in a container having a porous wall therein capable of containing molten aluminum in the container and being permeable by the molten electrolyte. Aluminum is electrolytically transported through the porous wall to a cathode thereby substantially separating the aluminum from alloying constituents.

Aluminum purification

A process for the production of aluminum chloride comprises providing a mixture of high purity activated carbon and alumina and bubbling chlorine gas therethrough, the mixture being kept at a temperature in the range of 500.degree. to 775.degree. C. Aluminum chloride is removed from the mixture as a vapor and condensed.

Aluminum chloride production

A process for purification of coal comprises forming an aqueous leaching solution containing nitric and hydrofluric acid. Impurities are removed by contacting coal having a mesh size not greater than 8 (Tyler Series) with the leaching solution for a period of 15 to 120 minutes at a temperature of 20.degree. to 100.degree. C. During the contacting of coal with leaching solution, a gaseous material such as air can be bubbled therethrough to provide additional mixing action and oxidant material. Thereafter, the solution is removed and the leached coal washed with water.

Coal purification and electrode formation

A process for the production of activated carbon from coal comprises contacting the coal with mineral acids to leach impurities therefrom and removing the leached coal from the mineral acids. Activated carbon is produced by calcining the leached coal at a temperature in the range of 550.degree. to 775.degree. C.

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Apollo, PA, United States of America

Subodh K Das