Mazda Co., Ltd.

Naoharu Miyazaki

Yuichi Yoshida

Mikio Nakatsukasa

The present invention relates to a phosphating method and solution for forming on a metal surface a phosphate film, which are used for elevating coating finish and rust-preventive property when a product consisting essentially of steel and/or zinc-plated steel combined with an aluminum alloy is coated with cationic electrocoating. The method and solution comprise that said metal surface is brought, to form a coating film, in contact with an aqueous phosphate solution which satisfies the following conditions with respect to the six kinds of ions contained. A total concentration of a sodium ion and a potassium ion is in a range of 2.0 to 15.0 (g/l). A total concentration of a manganese ion and a nickel ion is in a range of 1.0 to 5.0 (g/l). Concentration of a zinc ion is in a range of (1.6-0.02 T) to (2.5-0.02 T) (g/l). Concentration of a free F.sup.- ion is in a range of 8.0 T.sup.-1 to 20.0 T.sup.-1 (g/l), (here, T is temperature (.degree.C.) of a phosphating solution and in a range of 20 to 60). Contact of the metal surface with the phosphate solution is carried out with a combined process of dipping treatment subsequently followed by spraying treatment.

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Hiroshima, Japan

Naoharu Miyazaki