| 摘要 |
PROBLEM TO BE SOLVED: To provide a multilayer coating film structure formed with a chemical conversion treatment agent for an iron and/or zinc based base material suitably applicable to an iron based base material and a zinc based base material such as a cold rolled steel sheet and a zinc steel sheet, and capable of reducing the amount of sludge and the amounts of phosphorous, nitrogen and heavy metals causing environmental loads. SOLUTION: The multilayer coating film structure is composed of: a chemical conversion film formed on a base material; a cation electrodeposition coating film; an intermediate coating film; and a top coating film. The base material is composed of a ferrous base material, and the chemical conversion film is formed by treating the ferrous base material with a chemical conversion treatment agent for a ferrous base material comprising zirconium ions and/or titanium ions, and fluorine ions, and in which the content of the zirconium ions and/or the titanium ions is 50 to 300 ppm by weight, and the content of the fluorine ions is≥6 times by molar ratio to the zirconium ions and/or the titanium ions, and phosphoric acid ions are not substantially comprised, and whose pH is 2 to 4.3, and further performing water washing. In the chemical conversion film on the ferrous base material, the total content of the zirconium ions and the titanium ions is 20 to 40 mg/m<SP>2</SP>. COPYRIGHT: (C)2008,JPO&INPIT
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