Process for coloring anodized aluminum by AC electrolysis

US4917780A · kind A · utility

Assignee

• Henkel Kommanditgesellschaft auf Aktien · DE

Inventors

• Dieter Brodalla · Düsseldorf, DE
• Loert de Riese-Meyer · Goldkronach, DE
• Juergen Lindener · Goldkronach, DE

Key dates

• Filing date: Jul 19, 1989
• Grant date: Apr 17, 1990
• 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

Undesirable greenish tinges that normally result when coloring anodized aluminum by AC electrolysis in solutions of silver salts can be avoided by adding to the electrolytes an appropriate amount of p-toluenesulfonic acid and/or its salts. The coloring solution may also contain (i) sulfuric acid, (ii) alkali metal, ammonium and/or alkaline earth metal salts of sulfuric acid and/or (iii) alkali metal, ammonium and/or alkaline earth metal acetates.