Electrolytic iron metallizing of zinc surfaces

A method for metallizing pretreating galvanized or alloy-galvanized steel surfaces, comprising:

• contacting a galvanized or alloy-galvanized steel surface with an aqueous electrolyte, whose pH value is not greater than 9, wherein the aqueous electrolyte contains:
• (a) at least one water-soluble compound which is a source of cations of the element iron, wherein the total concentration of the at least one water-soluble compound is at least 0.001 mol/l relative to the element iron,
• (b) at least one accelerator selected from oxoacids of phosphorus, oxoacids of nitrogen, oxoacids of sulfur, salts of oxoacids of phosphorus, salts of oxoacids of nitrogen, salts of oxoacids of sulfur, and combinations thereof, wherein at least one of phosphorus, nitrogen, or sulfur atom of the oxoacids is present in an intermediate oxidation state, and
• (c) a total of less than 10 ppm of electro-positive metal cations selected from cations of elements Ni, Co, Cu, and Sn,
• wherein during a time of contact with the aqueous electrolyte, the galvanized or alloy-galvanized steel surface is switched for a period of the time of contact, at least temporarily to a cathode, wherein in this period, a cathodic electrolysis current in a range of 0.001 to 500 mA/cm2 is imparted to the galvanized or alloy-galvanized steel surface.