Aqueous corrosion protection formulation based on silanes

A method of coating comprising applying a composition to a surface, wherein said composition comprises:

• a binder,
• water,
• alcohol in a positive amount of less than 3% by weight, based on a total weight of the composition,
• at least one first additive selected from the group consisting of zinc powder, zinc flake, zinc dust, a powder or a flake or a dust of zinc alloys, a zinc-bismuth alloy, an aluminum powder, an aluminum flake, a powder or a flake or a dust of aluminum alloys, a magnesium powder, a magnesium flake, and a powder or a flake of magnesium alloys,
• a pH adjuster, and
• optionally a further additive,
• wherein:
• the composition has a pH of from 7.1 to 14,
• a dry residue of the binder is from 1% to 50% by weight, based on a total weight of the binder, and
• the binder comprises:
• a cocondensate based on an ω-glycidyloxyalkylalkoxysilane of formula I
• X—Si(R2)x(OR1)3-x (I),
• wherein X is a 2-(3,4-epoxycyclohexyl)ethyl, 1-glycidyloxymethyl, 2-glycidyloxyethyl, 3-glycidyloxypropyl or 3-glycidyloxyisobutyl group, R1 and R2 each independently are a linear or branched alkyl group comprising from 1 to 4 C atoms, and x is 0 or 1,
• a bis(alkoxysilylalkyl)amine of formula II
• (OR1)3Si-A-Si(OR1)3 (II),
• wherein each R1 independently is a linear or branched alkyl group comprising from 1 to 4 C atoms and A is a bis-amino-functional group of formula IIa
• —(CH2)i—[NH(CH2)f]gNH[(CH2)f*NH]g*—(CH2)i*- (IIa),
• wherein i and i* each independently are an integer of 1, 2, 3 or 4, f and f* each independently are an integer of 1 or 2, and g and g* each independently are an integer of 0 or 1,
• and optionally, at least one further silicon compound selected from the group consisting of tetraalkoxysilane, alkylalkoxysilane, mercaptoalkylalkoxysilane, carboxyalkylalkoxysilane, aminoalkylalkoxysilane, ureidoalkylalkoxysilane, thiocyanatoalkylalkoxysilane and a silica sol.