| 摘要 |
PROBLEM TO BE SOLVED: To enhance the adhesion property of a rust preventive film and to improve the corrosion resistance by executing an electrolytic treatment with a metallic material as a cathode with a specified current density to form a rust preventive film and coating the surface with a rust preventive coating agent having a specified compsn. SOLUTION: The electrolytic treatment is executed with a metallic material as a cathode with 0.1 to 50 A/dm2 current density in an aq. soln. contg. one or more kinds selected from among 0.2 to 100 g/l phosphoric ions, 0.2 to 100 g/l thiocarbonyl group-contg. compd., 0.2 to 100 g/l vanadic compd. and 0.2 to 100 g/l water-dispersible silica. In this way, on the surface of the metallic material, a 1st rust preventive film is formed to 1 to 1000 mg/m2 coating weight. Next, the surface of the film is coated with a rust preventive coating agent essentially consisting of a water base resin and water and contg. one or more kinds selected from among 0.2 to 50 g/l thicarbonyl group-contg. compd., 0.1 to 5 g/l phosphoric ions, 0.1 to 20 g/l vanadic compd. and 50 to 500 g/l water- dispersible silica to a thickness of 0.1 to 10μm to form a 2nd rust preventive film.
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