AQUEOUS SOLUTION CONTAINING AN INORGANIC SILICATE OR ALUMINATE, A FUNCTIONAL SILANE AND A NON-FUNCTIONAL SILANE AND METHOD FOR PRETREATING METAL WITH THIS SOLUTION

摘要

Painted metal sheet pretreated with an insoluble, composite layer containing siloxane. The composite layer is formed by rinsing the sheet with an alkaline solution containing at least 0.005M of a dissolved silicate or a dissolved aluminate, at least 0.1 vol.-% of an organofunctional silane and at least 0.02 vol.-% of a crosslinking-agent having two or more trialkoxysilyl groups. After the sheet is dried, the composite layer has a thickness of at least 10 ANGSTROM . After being painted, the siloxane forms a tenacious covalent bond between the paint and the metal substrate.