Supplementary corrosion protection for components made of organically precoated metal sheets

Abstract

The invention relates to a corrosion protection method for application in connection with the production of finished metallic components from organically precoated metal sheets. In the course of such production, areas of uncoated metal which inevitably come about in the course of cutting, forming and joining the precoated metal sheets are provided with a chromium-free corrosion protection coat that is not a zinc phosphate coating, which serves at the same time as a tie coat for the subsequent finish. The treatment solution preferably contains fluoro complexes of Ti, Zr and / or Si and also organic polymers. The invention also embraces a metallic component treated accordingly.

Description

FIELD OF THE INVENTION [0001] The invention relates to a corrosion protection method for application in connection with the production of finished metallic components from organically precoated metal sheets. In the course of such production, areas of uncoated metal which inevitably come about in the course of cutting, forming and joining the precoated metal sheets are provided with a corrosion protection coat which serves at the same time as a tie coat for the subsequent finish. BACKGROUND OF THE INVENTION [0002] Components joined from metal sheets, such as vehicle bodies, housings of domestic appliances or pieces of metal furniture, for example, may be put together from metal sheets which at that point do not have a coating providing permanent corrosion protection. In a process sequence which embraces a plurality of stages a coating providing permanent corrosion protection, composed of a conversion coat and a finish coat, can be produced after the metallic components have been asse...

AI Technical Summary

Benefits of technology

[0008] The object addressed by the invention, as part of an operation for producing finished metallic components which have been put together from metal sheets precoated with organic polymers, is to provide a simpler method than phosphating that allows corrosion protection and finish adhesion to be produced at the aforementioned sites of damage.

Problems solved by technology

Pretreatment prior to finishing, then, requires a plurality of treatment steps, which in turn necessitate a correspondingly extensive and therefore expensive pretreatment plant.

Additionally phosphating gives rise to wastes which contain heavy metal and require disposal, at great expense.

None of these alternative methods, however, has yet been able to displace phosphating as a pre-finishing pretreatment in auto making.

For that purpose, however, it is necessary to solve the problem that the assembly of bodies from organically precoated metal sheets inevitably gives rise to areas in which the organic coating is damaged or completely missing.

With organically coated metal substrates of this kind, however, the aforementioned areas with a damaged organic coat are particularly difficult to treat, since they differ in terms of their electrochemical potentials and their chemical reactivity from the customary metal surfaces.