Phosphating process

US5135583A · kind A · utility

Assignee

• Metallgesellschaft AG · DE

Inventors

• Horst Gehmecker · Hofheim, DE
• Thomas Kolberg · Heppenheim, DE
• Dirk Meyer · Frankfurt, DE
• Gerhard Muller · Grafing, DE

Key dates

• Filing date: Aug 23, 1991
• Grant date: Aug 4, 1992
• Expiry date: Aug 23, 2011

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C23C22/86
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

For phosphating metal surfaces which consist at least in part of aluminum, by means of phosphating solutions which contain zinc, phosphate and fluoride, any titanium which has entered the phosphating solution and would disturb the formation of the layer is precipitated by an addition of SiO-containing compounds and after the precipitate has been removed, the content of free fluoride is readjusted to the required concentration. Particularly suitable compounds which contain SiO, consist of alkali metasilicate, alkali orthosilicate and/or alkali disilicate, preferably used in an amount of 0.05 to 1 g/l of the phosphating solution, or of silica, which is preferably used in an amount of 0.5 to 10 g per liter of the phosphating solution (calc. as Si).