| 摘要 |
PROBLEM TO BE SOLVED: To provide a forming method of a multi-layered coating film by which performance of the coating film does not fall according as treating frequency increases when a bath containing a chemical conversion liquid consisting essentially of zirconium and containing no phosphoric acid is used and an aluminum workpiece is immersed in the bath to perform chemical conversion treatment. SOLUTION: The coating film forming method of an aluminum automobile body comprises a degreasing process, a chemical conversion treatment process in which the bath containing the chemical conversion liquid consisting essentially of zirconium, containing no phosphoric acid, containing aluminum ions and added by a fluorine ion supplying source compound, is used and while controlling pH of the chemical conversion liquid and a mass ratio of amount of fluorine added to the chemical conversion liquid to amount of the aluminum ions present in the chemical conversion liquid within an extent shown as a region A of figure, the chemical conversion liquid is applied on a surface to be coated by a dipping method and then is dried, a primer surfacer coating film forming process and a overcoating film forming process. COPYRIGHT: (C)2005,JPO&NCIPI
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