Method for treating metallic surfaces

A method of treating a metallic surface

• which comprises treating a metal-coated steel panel with a nonchromate metallic surface treating agent, containing, in each liter thereof,
• (a-1) a silane coupling agent and/or a hydrolytic condensation product thereof in amount of 0.01 to 100 g/l,
• (a-2) water-dispersible silica in a proportion of 0.05 to 100 g/l (solids), and
• (a-3) a zirconium compound in an amount of 0.01 to 50 g/l in terms of zirconium ion and/or a titanium compound in an amount of 0.01 to 50 g/l in terms of titanium ion,
• drying the treated steel panel and
• coating it with an anticorrosion coating agent containing, in each liter of an aqueous resin solution or dispersion,
• (b-1) a silane coupling agent and/or a hydrolytic condensation product thereof in an amount of 0.1 to 50 g/l,
• (b-2) water-dispersible silica in an amount of 10 to 500 g/l (solids) and
• (b-3) at least one phosphorus-containing ion selected from among phosphate ion, phosphite ion and hypophosphite ion in an amount of 0.1 to 10 g/l, and
• wherein said nonchromate metallic surface treating agent contains one or more members selected from among sulfide ion, thiosulfate ion, persulfate ion and a triazinethiol compound in a an amount of 0.01 to 100 g/l.