Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Depositing predominantly single metal or alloy coating on...
Patent
1995-06-06
1997-10-07
Gorgos, Kathryn L.
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Depositing predominantly single metal or alloy coating on...
205173, 205174, 205241, C25D 1122
Patent
active
056743718
ABSTRACT:
A process for providing a variety of light to medium colors of anodized aluminum or aluminum alloy which comprises the steps of anodizing an aluminum or aluminum alloy workpiece in an aqueous strong acid electrolyte solution such as a sulfuric acid solution by application of direct current at a current density of 5 to about 25 amperes per square foot and a temperature of from 55.degree. F. to 90.degree. F. to form on the workpiece a porous anodic oxide film having a thickness of at least about 3 microns; subjecting the resulting anodized workpiece to alternating current at a voltage of about 5 to about 25 volts for about 1 to 25 minutes in an aqueous strong acid electrolyte solution such as a sulfuric acid solution comprising about 1 to 15 volume percent of an organic carboxylic acid containing at least one reactive group in the alpha-position, wherein said reactive group is a hydroxy, amino, keto or carboxyl group; and electrolytically coloring the workpiece. In a preferred embodiment resulting in deepened color tones, including those in the blue to blue-gray and green range, one or more currentless "waiting periods" are maintained at various stages of the process during which essentially no current is applied to the workpiece in the electrolytic solution. In another embodiment, improved color uniformity is obtained by subjecting the workpiece prior to electrolytic coloring to a direct current pre-treatment step. The resulting electrolytically colored aluminum or aluminum alloy is particularly useful for architectural product.
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W. W. E Hubner and A. Schiltknecht, The Practical Anodizing Of Aluminum, MacDonald & Evans, London, 1960, pp. 21-29 no month available.
Battle Carl W.
Clariant Finance (BVI) Limited
Furman Diane E.
Gorgos Kathryn L.
Honor Robert S.
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