| abstract |
A zinc-plated steel material coated with a composite film, which is excellent in all of corrosion resistance, unsusceptibility to blackening, coating adhesion, and alkali resistance unlike plated steel materials treated by conventional chromate-substitute techniques. The zinc-plated steel material coated with a composite film has a composite coating film formed by applying on the surface of a plated steel material a treating liquid comprising a basic zirconium compound, a vanadyl (VO2+)-containing compound, a phosphoric acid compound, a cobalt compound, an organic acid, and water and having a pH of 7-14 and drying the liquid. It is characterized in that this composite coating film contains 10-45 mass% V, 5-100 mass% P, 0.1-20 mass% Co, and 10-90 mass% the organic acid based on the Zr. |