Patent ID: 7067177

Claim:
Process for coating an aluminum substrate, comprising the following steps: a) hydrolytic condensation, optionally in the presence of a condensation catalyst and/or additives, of hydrolysable starting components, wherein said hydrolysable starting components are: (i) a crosslinkable silane of the formula (II) R′″ m SiX (4−m) (II) in which the groups X, which can be identical or different, are selected from the group consisting of hydrogen, halogen, alkoxy, acyloxy, alkylcarbonyl, alkoxycarbonyl and NR″ 2 wherein each R″ is independently selected from the group consisting of H and alkyl, and the radicals R′″, which can be identical or different, are selected from the group consisting of alkyl, alkenyl, alkinyl, aryl, arylalkyl, alkylaryl, arylalkenyl, alkenylaryl, arylalkinyl and alkinylaryl, wherein said radicals can be interrupted by O or S atoms or the group —NR″ and can carry one or more substituents selected from the group consisting of halogens and optionally substituted amino, amide, aldehyde, keto, alkylcarbonyl, carboxyl, mercapto, cyano, hydroxyl, alkoxy, alkoxycarbonyl, sulphonic acid, phosphoric acid, acryloxy, methacryloxy, epoxide and vinyl groups, wherein m has the value 1, 2 or 3, and/or an oligomer derived therefrom, wherein the radical R′″ and/or the substituent is or includes a crosslinkable epoxide group, in an amount of 10 to 98 mol %, based on the total number of moles of the hydrolysable starting components, and (ii) an aluminium alkoxide of the formula (III) Al(OR′) 3 (III) wherein the radicals R′, which can be identical or different are selected from the group consisting of alkyl and —(CH 2 ) x —O—(CH 2 ) y —CH 3 , wherein x is an integer from 1 to 6 and y is an integer from 0 to 6, in an amount of 5 to 75 mol %, based on the total number of moles of the hydrolysable starting components, component (ii) being complexed, b) formation of a coating solution by addition of a prepolymer or reactive diluent, either of which is optionally crosslinkable with component (i), to the hydrolytic condensate obtained according to (a), wherein the prepolymer and the crosslinkable silane of the formula (II) form an interpenetrating network, and wherein the components do not include a non-crosslinkable silane; c) application of the coating solution obtained according to (b) to the aluminum substrate and drying of the coating solution to crosslink the hydrolytic condensate and/or the prepolymer and from a coating, wherein said coating exhibits improved adhesion to a tope layer and corrosion protection over the aluminum substrate.