Pretreating zinc surfaces prior to a passivating process

US10227686B2 · kind B2 · utility

Assignee

• Henkel AG & Co. KGaA · DE

Inventors

• Andreas Arnold · Werther, DE
• Michael Wolpers · Erkrath, DE
• Marcel Roth · Goldkronach, DE
• Uta Sundermeier · Leichlingen, DE

Key dates

• Filing date: Aug 22, 2014
• Grant date: Mar 12, 2019
• Expiry date: Sep 27, 2035

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C23C2222/00
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

The invention relates to a wet-chemical pretreatment of zinc surfaces prior to applying a corrosion-protection coating, which deposits a thin inorganic coating of oxide and/or metallic iron. An iron layer structure which is applied according to the invention, hereinafter referred to as ferrization, improves the achievable corrosion protection of wet-chemical conversion coatings on zinc surfaces. Furthermore, the ferrization process causes both a reduction of the contact corrosion of joined metal components which have zinc and iron surfaces as well as a reduction of corrosive coating migration on cut edges of galvanized steel strips with coating layer structures. In particular, the invention relates to an alkaline composition containing an iron ion source, a reducing agent based on oxoacids of nitrogen and phosphorus, and water-soluble organic carboxylic acids with an amino group at the α, β, or γ position with respect to the acid group and/or the water-soluble salts thereof.