Mercedes-benz Aktiengesellschaft

Werner Funke

Fritz Mezger

Anja Keller

Ute Flammer

The present invention relates to a painted sheet metal part, such as a car body, with a polyacid layer between the coat of paint and the surface of the sheet metal part and to a method for applying such a coating on the part before painting. Initially, the part is cleaned and de-greased, and subsequently the polyacid layer is deposited and stabilized. In order to be able to apply this layer without losing wet adhesion qualities of the coat of paint and the anti-corrosive effect of coating layer, while presenting fewer ecological disadvantages or harmful consequences, polyacids, which comprise homopolymers or copolymers of carboxylic acids containing double bonds or of functional esters of carboxylic esters, or copolymers of carboxylic acids with vinyl compounds, are used pursuant to the present invention as the protective bonding layer. The polyacids used are further combined with polymers having a glass transition temperature above 100.degree. C., such as phenolic resins, urea resins or epoxy resins, and/or with low molecular carboxylic acids with 2 to 30 carbon atoms in the carbon chain, in order to increase the corrosion protection effect. The deposited anti-corrosion layer is stabilized by thermal curing at about 100.degree. to 150.degree. C. The polymers of the corrosion inhibitor layer can be crosslinked intermolecularly, intramolecularly or with the adjacent paint layer with functional groups which are not absorbed by the substrate.

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Leonberg, Germany

Werner Funke