Patent ID: 8679586

Claim:
A method for anticorrosion pretreatment of metal surfaces in a processing sequence comprising a conversion treatment stage (D) with an aqueous composition (1) containing in total at least 50 ppm of one or more of elements B, Si, Ti, Zr and Hf in the form of water-soluble compounds at a pH value of 3 to 5.5, wherein the metallic surfaces pass in succession through at least treatment stages of: (A) optionally degreasing and cleaning; (B) optionally rinsing with process water optionally containing part of the aqueous composition of the degreasing and cleaning stage (A); (C) prerinsing with water containing in total at least 10 ppm of elements B, Si, Ti, Zr and/or Hf in the form of water-soluble compounds; (D) conversion treatment with the aqueous composition (1); (E) postrinsing with water containing part of the aqueous composition (1) of treatment stage (D); (F) optionally second postrinsing with water containing part of the aqueous composition of postrinsing stage (E), wherein the aqueous composition (1) of the conversion treatment stage (D) contains a proportion of fluorine bound in the form of fluoro complexes of the one or more elements B, Si, Ti, Zr and Hf or fluorine in excess and unbound in the form of free fluoride, and wherein pH value in the prerinsing stage (C) is in a range from 5 to 7.0, and wherein a cascaded recirculation of aqueous medium from the final rinsing stage to the first rinsing stage proceeds such that in total at least 10 ppm of the elements B, Si, Ti, Zr and/or Hf in the form of water-soluble compounds are present in the prerinsing stage (C).