Wet on wet method and chrome-free acidic solution for the corrosion control treatment of steel surfaces

Abstract

A process for anticorrosion treatment of bare metal surfaces comprising steel surfaces, wherein the bare metal surfaces are contacted with an acidic aqueous solution of a fluoro complex of at least one element M selected from the group B, Si, Ti, Zr and Hf, at least one further component which is selected from among: a buffer system for the pH range from 2.5 to 5.5, nitrate ions, copper ions, silver ions, vanadium or vanadate ions, bismuth ions, magnesium ions, zinc ions, manganese ions, cobalt ions, nickel ions, tin ions, aromatic carboxylic acids with at least two groups containing donor atoms, or derivatives of such carboxylic acids, and silica particles with an average particle size of below 1 μm; and contains no more than 1 mg / l of an organic polymer with allylamine or vinylamine monomers; the metal surfaces are then rinsed with water and thereafter are coated with a cathodically depositable electro-dipcoating.

Description

[0001]This application is a continuation under 35 U.S.C. Sections 365(c) and 120 of International Application No. PCT / EP2006 / 011696, filed 6 Dec. 2006 and published 14 Jun. 2007 as WO 2007 / 065645, which claims priority from German Application No. 102005059314.3, filed 12 Sep. 2005, each of which is incorporated herein by reference in its entirety.[0002]The present invention relates to a novel product for the anticorrosion treatment of metal surfaces. In addition, a process is provided for the anticorrosion treatment of metal, in particular, steel surfaces. The anticorrosion treatment is primarily intended as a pre-treatment for a subsequent cathodic electro-dipcoating.[0003]Anticorrosion agents that involve an acidic aqueous solution of fluoro complexes have been known for some considerable time. They are increasingly employed as a replacement for chromating processes that due to the toxicological properties of chromium compounds are less and less used. Generally, solutions of fluor...

AI Technical Summary

Benefits of technology

[0003]Anticorrosion agents that involve an acidic aqueous solution of fluoro complexes have been known for some considerable time. They are increasingly employed as a replacement for chromating processes that due to the toxicological properties of chromium compounds are less and less used. Generally, solutions of fluoro complexes of this type contain additional anticorrosion agents that further improve the corrosion protection and paint adhesion.

Problems solved by technology

Accordingly, a drying step, in which the pre-treatment layer can be, for example, chemically modified and / or hardened by dewatering, is not desired.

However, the presence of organic polymers in pre-treatment solutions is frequently undesirable as they can lead to difficulties in the waste water treatment.

One drawback of the prior art is that with steel surfaces that have not been pre-treated, the previously stated requirements can only be satisfied up to now with a layer-forming zinc phosphatization.

Compared with the standard of the layer-forming zinc phosphatization, a pre-treatment with aqueous solutions of fluoro complexes shows significant disadvantages in regard to corrosion protection and adhesion to paint when the pre-treated surfaces are not dried before painting.