Electrocoating chrome-plated steel
AssigneeUnited States Steel Corporation
InventorsJian X. Li, Daniel E. Bullard, Chyang J. Wu
Life of this patent
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Abstract
Steel cabinet parts and other steel objects are electrocoated in a cationic resin-containing bath. The steel objects are chromium-coated, free of phosphate and preferably free of chromium oxide. The products are not significantly subject to filiform corrosion, and the process is economically beneficial because throwpower is more easily controlled than in previous processes.
Claims20
Method of making an appliance cabinet preform comprising (a) providing a steel strip, said steel strip having a chromium coating and being substantially free of phosphate, (b) forming a portion of said steel strip into a desired three-dimensional shape which is at least part of an incipient appliance cabinet preform, (c) immersing said three-dimensional shape as a cathode into an electrolytic cell containing an aqueous coating bath comprising a cationic polymer (d) holding said three-dimensional shape in said electrolytic cell under coating conditions for a residence time sufficient to form an adherent coating on said three-dimensional shape, (e) removing said three-dimensional shape from said bath, and (f) baking said three-dimensional shape including said adherent coating.
An appliance cabinet part comprising a piece of steel strip having a chromium undercoat and being substantially free of phosphate, said piece of steel strip being formed into a three-dimensional shape suitable for an appliance cabinet part and having a coating of crosslinked cationic polymer deposited from an aqueous electrolytic bath.
Method of coating steel comprising electrocoating tin-free steel, said tin-free steel being substantially free of phosphate as a cathode under a direct current in a bath comprising a cationic polymer.
Method of operating an electrolytic coating line wherein a steel object to be coated is placed as a cathode in a bath of coating composition comprising a cationic polymer in an electrolytic cell and subjected to an electric current in said bath for a residence time therein until a coating of a desired thickness on at least a first target area of the surface of said steel object is achieved for drying or curing, comprising (a) utilizing as said steel object an object made of steel having a coating of chromium metal and being substantially free of phosphate (b) determining a range of residence times necessary to achieve said desired coating thickness on said first target area under a range of power conditions, and (c) employing a selected combination of power and residence time for said object within said bath.
Dependencies are inferred from the claim text.