Protective material made of corundum crystals
AssigneeSwiss Aluminium Ltd.
InventorsHanspeter Alder, Hans Boving
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Abstract
A molten salt charge as used in the electrolysis of aluminum contains aluminum oxide in excess of the eutectic composition and is cooled at a surface colder than the melt in such a way that the aluminum oxide precipitates onto this surface in the form of corundum crystals. Such a layer of crystals provides chemical and electrical insulation to the cooling surface under the corrosive conditions produced by the charge.
Claims14
In a process for forming a compact crust in the electrolysis of aluminum in a molten electrolyte, for use in protecting a surface portion of an object against both chemical and electrical reactions, the steps comprising:
- forming a molten salt charge comprising an aluminum oxide content in excess of the eutectic composition of said charge;
- placing said surface portion in contact with said charge;
- and
- cooling said surface portion sufficiently to precipitate at least part of the aluminum oxide onto said surface portion in the form of corundum crystals, whereby said crust is formed.
Dependencies are inferred from the claim text.