Method for passivating metallic surfaces with aqueous compositions comprising surfactants

A method for passivating a metallic surface, comprising contacting a metallic surface with an aqueous composition comprising the following components:

• a) at least one water-soluble polymer (X) comprising acidic groups, the polymer (X) having at least 0.6 mol of acid groups/100 g of polymer;
• b) at least one surfactant of the general formula (T1)
• where
• Ra is a branched or linear alkyl radical having 8 to 18 carbon atoms,
• x is an integer from 2 to 12,
• y is an integer from 1 to 10,
• Rb is hydrogen or a branched or linear alkyl radical having 1 to 4 carbon atoms,
• Rc is hydrogen or a branched or linear alkyl radical having 1 to 4 carbon atoms,
• with the proviso that at least one radical, Rb or Rc, is not hydrogen;
• c) optionally at least one cosurfactant (T2);
• and
• d) at least one solvent (L), comprising at least 80% by weight of water;
• the pH of the composition being in the range from 0.5 to 5.