Aqueous electrocoating materials comprising a silane-containing crosslinker

An aqueous electrocoating material (ECM), comprising—based on a total weight of the electrocoating material—

• (a) at least one binder (B) containing cationic or anionic groups and reactive functional groups which are able to undergo crosslinking reactions with complementary reactive functional groups present in a crosslinking agent (CA),
• (b) at least one crosslinking agent (CA) containing fully blocked isocyanate groups and at least one silane group;
• (c) at least 100 ppm bismuth;
• (d) at most 300 ppm of dissolved lithium;
• and
• (e) optionally at least one additive (AD);
• wherein
• the at least one crosslinking agent (CA) is prepared by
• (i) reacting 0.01 to 5 mol-% of a total amount of free isocyanate groups present in at least one parent structure P with at least one compound of general formula (I)
• HN[X-SiR1a(OR2)3-a]n[X′-SiR1b(OR2)3-b]m[R3]2-(m+n) (I)
• wherein
• X, X′ represent, independently from each other, linear and/or branched alkylene or cycloalkylene radicals having 1 to 20 carbon atoms;
• R1 represents an alkyl, cycloalkyl, aryl, or aralkyl group, it being possible for the carbon chain to be interrupted by nonadjacent oxygen, sulfur, or NRa groups, where Ra is alkyl, cycloalkyl, aryl, or aralkyl;
• R2 represents hydrogen, an alkyl, or a cycloalkyl group, it being possible for the carbon chain to be interrupted by nonadjacent oxygen, sulfur or NRa groups, where Ra is alkyl, cycloalkyl, aryl, or aralkyl;
• R3 represents a linear and/or branched alkylene or cycloalkylene radicals having 1 to 20 carbon atoms;
• n,m are, independently from each other, 1 or that m is 1 and n is 0;
• and
• a,b are, independently from each other 0 to 2;
• (ii) reacting the free isocyanate groups of the parent structure P remaining after step (i) with at least one blocking agent BA to obtain the crosslinking agent (CA) comprising fully blocked isocyanate and silane groups;
• and
• (iii) optionally diluting the crosslinking agent (CA) obtained in step (ii) with at least one solvent.