Patent ID: 7427442

Claim:
A coating on a metal to protect against corrosion, comprising the following layer sequence: (i) metal surface, (ii) cured layer based on a sol containing silicon compounds and having a pH of from 1 to 6, wherein the sol used to produce the sol layer (ii) is based on at least one tetraalkoxysilane and/or at least one alkylalkoxysilane, wherein the sol used to produce the sol layer (ii) is based on at least one alkoxysilane selected from the group consisting of tetramethoxysilane, methyltrimethoxysilane, propyltrimethoxysilane, isopropyltrimethoxysilane, octyltrimethoxysilane, hexadecyltrimethoxysilane, octadecyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, propyltriethoxysilane, isopropyltriethoxysilane, octyltriethoxysilane, hexadecyltriethoxysilane, and octadecyltriethoxysilane or a mixture of at least two of the aforementioned alkoxysilanes, (iii) cured layer based on at least one organosilane selected from the group consisting of 3-aminopropyltrimethoxysilane, 3-aminopropyl-triethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyl-methyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyl-methyldiethoxysilane, N,N-di(2-aminoethyl)-3-aminopropyltrimethoxysilane, N,N-di(2-aminoethyl)-3-aminopropyltriethoxysilane, N-[N′-(2-aminoethyl)-2-aminoethyl)]-3-aminopropyltrimethoxysilane, N-[N′-(2-aminoethyl)-2-aminoethyl)]-3-aminopropyltriethoxysilane, N-methyl-3-aminopropyltrimethoxysilane, N-methyl-3-aminopropyltriethoxysilane, N-(n-butyl)-3-aminopropyltrimethoxysilane, N-(n-butyl)-3-aminopropyltriethoxysilane, N-cyclohexyl-3-aminopropyltrimethoxysilane, N-cyclohexyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-aminopropylmethyldimethoxy-silane, 3-aminopropylmethyldiethoxysilane, bis(3-trimethoxysilylpropyl)amine, and bis(3-triethoxysilylpropyl)amine or at least one fluoro-functional organosilane of the general formula R 1 —Y u —(CH 2 ) 2 Si(R 2 ) y (OR) 3-y , where R 1 is a mono-, oligo- or perfluorinated alkyl group having from 1 to 13 carbon atoms or a mono-, oligo- or perfluorinated aryl group, Y is a —CH 2 —, —O— or —S— group with u being 0 or 1, R 2 is a linear, branched or cyclic alkyl group having 1 to 8 carbon atoms or is an aryl group, and y is 0 or 1, or a mixture of at least two of the aforementioned organoalkoxysilanes or a partial hydrolysate of the aforementioned organosilanes or an aqueous-alcoholic solution of at least one organosilane, and (iv) optionally, one or more coating films.