Use of an adhesion promoter obtainable as a reaction product of a di- or poly amine with α,β-unsaturated carboxylic acid derivatives for metal surface treatment

A painted metal substrate comprising a mixed organic/inorganic intermediate layer consisting of oxides, hydroxides and/or oxyfluorides of the elements Zr, Ti and/or Si and organic compounds having at least one tertiary amine group that is linked via a bridge-forming divalent functional group to the carbonyl carbon atom of an amide group, wherein the bridge-forming divalent functional group has two carbon atoms as bridge atoms and at least one secondary amine group which is linked via at least one bridge-forming divalent functional group to a carbonyl carbon atom of an amide group, the bridge-forming divalent functional group having two carbon atoms as bridge atoms.

A method of improving paint adhesion to metal surfaces comprising pretreating the metal surfaces before painting with a pretreatment comprising an adhesion promoter selected from organic compounds having at least one tertiary amine group that is linked via a bridge-forming divalent functional group to the carbonyl carbon atom of an amide group, the bridge-forming divalent functional group having two carbon atoms as bridge atoms, and at least one secondary amine group which is linked via at least one bridge-forming divalent functional group to a carbonyl carbon atom of an amide group, the bridge-forming divalent functional group having two carbon atoms as bridge atoms;

• wherein the adhesion promoter is present in an amount of at least 0.005 g/kg, but no more than 5 g/kg;
• wherein the organic compounds have a weight-average molar mass that is greater than 500 g/mol.