Patent ID: 8293334

Claim:
A method for metallizing pretreatment of galvanized or alloy-galvanized steel surfaces, comprising: I. contacting a galvanized or alloy-galvanized steel surface with an aqueous agent ( 1 ), having a pH no greater than 9, thereby producing a metallized pretreated galvanized or alloy-galvanized steel surface, said aqueous agent ( 1 ) comprising: (a) cations and/or compounds of a metal (A), said metal selected from the group consisting of iron, molybdenum, tungsten, cobalt, nickel, lead, tin and mixtures thereof in a concentration of at least 0.001M, and (b) accelerators selected from the group consisting of oxo acids of phosphorus, oxo acids of nitrogen, salts of oxo acids of phosphorus and salts of oxo acids of nitrogen, wherein at least one phosphorus atom or nitrogen atom is present in a medium oxidation stage of said accelerators such that said accelerators have a reducing effect, the aqueous agent ( 1 ) having a molar ratio of accelerators to the concentration of cations and/or compounds of metal (A) of at least 1:5; and the cations and/or compounds of metal (A) having a redox potential E redox measured on a metal electrode of the metal (A) at a predetermined process temperature and concentration of cations and/or compounds of the metal (A) in the aqueous agent ( 1 ); the galvanized or alloy-galvanized steel surface having an electrode potential E Zn when in contact with an aqueous agent ( 2 ) differing from the agent ( 1 ) only in that the aqueous agent ( 2 ) does not contain any cations and/or compounds of the metal (A), wherein the redox potential E redox is more anodic than the electrode potential E Zn ; whereby metallic coatings are deposited on the galvanized or alloy-galvanized steel surface said metallic coatings comprising at least 50 atomic % of the metal (A) present in a metallic state.