Patent ID: 8956468
Filing Date: 2015-02-17
Classification: C23C,Y10T

Abstract:
1. A method for the anticorrosion conversion treatment of metallic surfaces which, in addition to surfaces of steel and/or galvanized steel and/or alloy-galvanized steel, also comprise surfaces of aluminum, comprising: contacting cleaned and degreased metallic surfaces with an aqueous acidic composition comprising: (a) 5-50 g/l phosphate ions; (b) 0.3-3 g/l zinc(II) ions; (c) one or more water-soluble compounds of zirconium present in an amount of 5-70 ppm, relative to elemental zirconium; and (d) 22-90 ppm of free fluoride; and having a quotient λ corresponding to formula (I): F/mM and Me/mM respectively denoting the free fluoride (F) concentration in mM and zirconium concentration (Me) in mM, in each case divided by unit of concentration of mM, said quotient λ being at least 4, but no more than 7.1; thereby forming an uninterrupted crystalline phosphate coating layer on the steel, galvanized steel and alloy-galvanized steel surfaces and a noncrystalline conversion coating layer on the aluminum surfaces.