Patent ID: 7905964

Claim:
A process for the passivation of the surface of a strip metal by means of a continuous process by treatment of the surface with an acidic, chromium-free aqueous preparation comprising at least one water-soluble polymer X comprising acidic groups, wherein (1) the polymer has at least 0.9 mol of acid groups/100 g of the polymer and is a copolymer X1 comprising the following monomeric units based in each case on the amount of all monomers incorporated as polymerized units in the copolymer: (A) from 40 to 90% by weight of (meth)acrylic acid; (B) from 5 to 60% by weight of at least one further monoethylenically unsaturated monomer which differs from (A) and has one or more acidic groups and is selected from the group consisting of: (B1) monoethylenically unsaturated dicarboxylic acids having 4 to 7 carbon atoms; and/or (B2) monoethylenically unsaturated phosphoric and/or phosphonic acids; and (C) optionally from 0 to 30% by weight of at least one further ethylenically unsaturated monomer differing from (A) and (B); (2) the pH of the preparation is not more than 5; (3) the amount of the polymer is from 15 to 25% by weight, based on the amount of all components of the preparation; (4) the preparation furthermore comprises at least one wax having a melting point from 100° C. to 160° C. and wherein said wax comprises oligomeric or polymeric substances having a molecular weight M n greater than 400 g/mol, and having a proportion by weight of more than 60% by weight of structural elements selected from the group consisting of (—CH 2 —CH 2 ), (—CH 2 —CH<), (CH 2 —CH(CH 3 )—),(—CH 3 ), (—CR 2 —CR 2 —), and (—CR 2 —CR(CR 3 )—), wherein R is H and/or F, and with the proviso that said structural elements are linked to one another so that they predominantly comprise units of at least 12 carbon atoms linked directly to one another; (5) the amount of the wax is from 1 to 18% by weight, based on the total amount of all polymers X; and (6) the application of the aqueous preparation is performed by means of coating rolls.