Method for electrolytic coloring of aluminum surfaces using alternating current

US5587063A · kind A · utility

Assignee

• Henkel Kommanditgesellschaft auf Aktien · DE

Inventors

• Peter Kuhm · Hilden, DE
• Christine Schroeder · Goldkronach, DE
• Volker Sander · Hilden, DE
• Juergen Lindener · Goldkronach, DE
• Loert de Riese-Meyer · Goldkronach, DE

Key dates

• Filing date: Jul 28, 1995
• Grant date: Dec 24, 1996
• Expiry date: Jul 28, 2015

Classification

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

Abstract

Anodized aluminum surfaces are electrolytically colored using alternating current in a process in which two different coloring baths are sequentially employed. One bath contains copper(II) ions and an additive which improves throwing power thereby providing uniform distribution of the depth of color. The other bath contains tin(II) ions, silver ions, or both tin(II) and silver ions. If tin(II) ions are included, additives which stabilize tin(II) ions and improve throwing power are also included. Either bath may be used first. The use of two separate coloring baths provides colored aluminum surfaces which have excellent resistance to corrosion. Workpieces with reddish-gold hues and darker tones can be produced.