Patent ID: 8801871

Claim:
An aqueous composition for the anticorrosion conversion treatment of metallic surfaces, which comprise surfaces of steel or galvanized steel or alloy-galvanized steel or aluminum and any combinations thereof, said composition, being acidic and 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): λ = F ⁢ / ⁢ mM Me ⁢ / ⁢ mM ( 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.