| 摘要 |
PURPOSE:To enhance the long-term corrosion-proof capacity of a film, by treating a metal material, which is treated with a chromate solution containing a water-soluble compound, with a painting pretreatment agent containing a chromium compound containing hexavalent chromium having a specific range of solubility. CONSTITUTION:A metal material cleaned by degreasing treatment is at first contacted with a chromate solution comprising a water-soluble chromium compound with solubility of above 20, aqueous silica and an aqueous resin. After drying, the treated metal material is subsequently treated with a chromate solution containing a chromium compound containing hexavalent chromium with solubility of 20-10<-5>, aqueous silica and an aqueous resin and dried as it is without performing washing. The obtained protective film is stable to thermal deterioration and shows corrosion resistance and imparts excellent corrosion resistance to the metal material over a long period of time without reacting with the resin component of a clear or top coat paint.
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