Process of forming phosphate coatings on metals

US4950339A · kind A · utility

Assignee

• Metallgesellschaft AG · DE

Inventors

• Horst Gehmecker · Hofheim, DE
• Werner Rausch · Hopewell Junction, US
• Peter Jorns · Frankfurt am Main, DE

Key dates

• Filing date: Feb 1, 1989
• Grant date: Aug 21, 1990
• Expiry date: Feb 1, 2009

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C23C22/78
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

A process to form phosphate coatings on individual parts of metal which at least on part of their surface consists of iron or steel. The individual parts are contacted at a temperature in the range of from 60 to 100 degrees centigrade for 3 to 30 seconds with an aqueous phosphating solution which contains 10 to 80 g/l zinc, 12 to 80 g/l phosphate (calculated as P.sub.2 O.sub.5), 40 to 150 g/l nitrate and, in addition 0.1 to 10 g/l fluoride, 0.01 to 10 g/l nickel, 0.0001 to 0.1 g/l copper, and may also contain tartaric acid, citric acid and/or manganese and in which the ratio of free acid to total acid has been adjusted to (0.1 to 0.3):1 and which contains at least 80 points of total acid and is virtually free of iron(II) ions. Prior to phosphating treatment, the individual parts may be cleaned and may optionally be treated to remove rust, scale and phosphate layers and/or be activated. After the phosphating treatment they may be passivated with an after-rinse solution. Each of said process steps is carried out for 3 to 30 seconds.