| 摘要 |
The object of this present invention is to provide novel means for inhibiting elution of hexavalent chromium from a chemical conversion coating. A composition for chemical conversion treatment comprises at least 0.1 g/L of a polyphenol and at least 1.5 g/L in chromium ion equivalent of an aqueous trivalent chromium compound and has a pH of 6 or less. A chemical conversion coating formed on a metallic surface of a member by contacting the surface with the composition for chemical conversion treatment has a hexavalent chromium content of 0.04 μg/cm2 or less after exposure to an environment having a temperature of 80 degrees C. and a relative humidity of 100% for 120 hours. The content of hexavalent chromium is measured by a method compliant with EN15205. A composition containing at least 0.1 g/L of a polyphenol can be used as a composition for post-coating treatment of a chemical conversion coating obtained by conventional chemical conversion treatment.
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