Nippon Paint Compnay, Ltd.

Koetsu Endo

Akio Tokuyama

Tamotsu Sobata

Yasutake Mino

Masahiro Jo

Takamasa Shimizu

The present inventin concerns a process for phosphating a metal surface comprising treating a metal surface with an acidic aqueous phosphate solution comprising zinc ion, phosphate ion, a phosphating accelerator and particular concentration of colloidal particles having an isoelectric point of 3 or less and an average particle diameter of 0.1.mu. or less, the metal surface being iron-based surface, zinc-based surface or combination thereof and the resulted phosphate coating being excellent in film adhesion, corrosion resistance and especially scab corrosion resistance.

Phosphate coatings for metal surfaces

A zinc phosphate film on a metal surface is used as a surface-protecting film and an under coating film for coating and so on. The zinc phosphate film is formed by treating a metal surface with an aqueous zinc phosphate solution. The aqueous zinc phosphate solution includes solutions containing a zinc ion in a concentration of more than 2 g/l to 20 g/l, a phosphate ion in a concentration of 5 g/l to 40 g/l, and at least one of silicotungstic acid and a silicotungstate in a concentration of 0.005 g/l to 20 g/l measured in terms of tungsten content.

Method for forming zinc phosphate film on metal surface

A process for phosphating the surfaces of iron-based metals, zinc-based metals or combination of such surfaces by treating the metal surfaces with an aqueous acidic zinc-phosphating solution comprising from about 0.1 to about 200 g/l of zinc ion, from about 5 to about 40 g/l of phosphate ion, from about 0.01 to 20.0 g/l as tungsten of soluble tungsten compound and a conversion coating accelerator. The metal surfaces thus phosphated with the solution are suitable for electrocoating.

Process for phosphating metal surfaces

Disclosed is a surface treating agent which improves the adhesive properties between a metal surface and a paint layer thereon. The surface treating agent is an acidic aqueous solution comprising zinc ions, nickel ions and phosphate ions, characterized by adding a cyclic metaphosphate thereto in the form of (MPO.sub.3).sub.n wherein M represents a metal atom and n is

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Kyoto, Japan

Koetsu Endo