Pretreatment of aluminum surfaces with chrome-free solutions

US6562148B1 · kind B1 · utility

Assignees

• CHEMETALL GMBH · DE
• Bayerische Motoren Werke Aktiengesellschaft · DE

Inventors

• Thomas Wendel · Schwalbach, DE
• Klaus Bittner · Frankfurt am Main, DE
• Hardy Wietzoreck · Frankfurt am Main, DE
• Peter Muller · Neuhausen, CH

Key dates

• Filing date: Jan 23, 2002
• Grant date: May 13, 2003
• Expiry date: Jan 23, 2022

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C23G1/125
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

In a method for the pretreatment of work pieces having a surface made of aluminium or aluminium alloys, for non-cutting shaping and/or the connection by welding or gluing to work pieces as well as for a subsequent permanent corrosion-preventing treatment, the work pieces are subjected to a three-stage treatment bya) rinsing with an aqueous, acidic solution containing a mineral acid,b) rinsing with water,c) bringing them into contact with an aqueous, acidic solution which is chromium-free and polymer-free and contains Ti and Zr as complex fluorides in a weight ratio of Ti:Zr of 2:1 to 1:2, in such a way that, after the subsequent drying off, a layer weight of 2 to 15 mg/m2 (calculated as Ti/Zr metal) results, wherein depending on the type of application, solutions having different concentrations and different pH values are used.