| 摘要 |
PROBLEM TO BE SOLVED: To remarkably improve the appearance of steel in the meanwhile from the point after treatment to the time in which same surface is replaced by stable rust by depositing a film containing a resin having minus fixed charges and salt composed of anions and counter cations having trapping and depositing action to iron ions on a structure. SOLUTION: As the anions having trapping and depositing action to iron ions in the film, phosphate ions and/or molybdate ions are preferable. The content of the salt composed of anions and counter cations is suitably controlled to 1 to 10 pts.wt. per 100 pts.wt. of the film. Preferably, the resin having minus fixed charges is a reaction product of a fatty acid modified epoxy resin and carboxylic anhydride having a free anionic functional group such as a carboxyl group and a sulfonic group and is incorporated by 20 to 50 pts.wt. in 100 pts.wt. of the film. Suitably, pigment of 30 to 70 pts.wt. is incorporated into the film of 100 pts.wt. to prevent appearance abnormality such as the blistering of the film and the filmlike peeling of the film.
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