Anticorrosion coating method for zinc-plated steel structure

An anticorrosion coating method for a galvanized steel structure, the method comprising applying an undercoating composition (I) to a cured thickness of 10 to 200 μm to a surface of a galvanized steel structure, and then applying thereto an overcoating composition (II) to a cured thickness of 100 to 1,500 μM;

• the undercoating composition (I) comprising an epoxy resin (A) having two or more epoxy groups per molecule;
• at least one resin (B) selected from the group consisting of urethane-modified epoxy resins obtained by reacting polyisocyanate compounds with amine-added epoxy resins, and petroleum resins;
• and an amine-based curing agent (C);
• the amount of the resin (B) being 10 to 300 parts by weight per 100 parts by weight of solids of the resin (A);
• the undercoating composition (I) having a shrinkage stress of 20 kg/cm2 or less when it is in the form of a 50 μm-thick coating film cured at 23° C. for 30 days after application;
• the overcoating composition (II) comprising an epoxy resin (D) having two or more epoxy groups per molecule, a glass flake (E), and an amine-based curing agent (F);
• and the amount of the glass flake (E) being 5 to 100 parts by weight per 100 parts by weight of solids of the resin (D)
• wherein the epoxy resin (A) is obtained by reacting at least one polyhydric phenol selected from the group consisting of bisphenol A and bisphenol F with epichlorohydrins, and
• the epoxy resin (D) is obtained by reacting at least one polyhydric phenol selected from the group consisting of bisphenol A and bisphenol F with epichlorohydrins.