Chromium-free process for the no-rinse treatment of aluminum and its alloys and aqueous bath solutions suitable for this process

US5868872A · kind A · utility

Assignee

• Henkel Kommanditgesellschaft auf Aktien · DE

Inventors

• Uwe Karmaschek · Bergheim, DE
• Raschad Mady · Frechen, DE

Key dates

• Filing date: Oct 25, 1996
• Grant date: Feb 9, 1999
• Expiry date: Oct 25, 2016

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C23C22/361
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

Described is a process using a no-rinse technique for the production of a chromium-free conversion layer on the surface of aluminum and its alloys by treating with an aqueous solution having a pH between 1 and 3.5 and containing titanium and/or zirconium plus an organic film-forming agent. The process is characterized in that the surface is brought into contact with a solution containing a) 2.2 to 22.0 g/l of Zr(IV) and/or 1.4 to 14.0 g/l of Ti(IV), b) 2.4 to 24.0 g/l of orthophosphate, c) 3.0 to 30.0 g/l of fluoride, d) 0.15 to 1.5 g/l of a water-soluble or homogeneously water-dispersible organic film former and, after a contact time between 1 and 40 seconds, the wet surface is allowed to dry, without rinsing, at a temperature between 50.degree. and 125.degree. C. Also described are aqueous concentrates for use in the process.