Process for dyeing anodized aluminum

US5064512A · kind A · utility

Assignee

• Henkel Kommanditgesellschaft auf Aktien · DE

Inventors

• Dieter Brodalla · Düsseldorf, DE
• Juergen Lindener · Goldkronach, DE
• Loert de Riese-Meyer · Goldkronach, DE
• Willi Wuest · Ratingen, DE
• Christine Schroeder · Goldkronach, DE
• Willi Buchmeier · Goldkronach, DE
• Juergen Foell · Goldkronach, DE

Key dates

• Filing date: Jul 19, 1989
• Grant date: Nov 12, 1991
• Expiry date: Jul 19, 2009

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C25D11/22
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

Substituted diphenols, phenyl ethers containing two oxygen atoms attached to a benzene nucleus, and naphthols are more practically effective than previously known additives in stabilizing tin (II) salts, in electrolyte solutions useful for coloring anodized aluminum by electrolysis therein, against oxidation to tin(IV) by reaction with ambient oxygen. Preferred additives include 2-tert-butyl-1,4-dihydroxybenzene, methylhydroquinone, trimethylhydroquinone, 4-hydroxynaphthalene-2,7-disulfonic acid, and p-hydroxyanisole. If p-toluenesulfonic acid or napthalene sulfonic acid are also used in the electrolyte, the throwing power can be greatly improved.