Metal surface treatment method and surface-treated steel sheet

PROBLEM TO BE SOLVED: To provide a metal surface treatment method and a surface-treated steel plate formed by the method capable of suppressing irregular coating even when executing the chromate-free surface treatment of the steel plate having large surface unevenness, and ensuring sufficient corrosion resistance while preventing any increase in the coating film thickness. SOLUTION: In the metal surface treatment method, water-based metal surface treatment agent containing at least silane coupling agent and surfactant is applied on a surface of a galvanized steel plate having the surface roughness of ≥1 μm and ≤10 μm in terms of Ra, and the steel plate is dried to form a coating film on the surface of the galvanized steel plate. The water-based metal surface treatment agent is formed of liquid particles having the particle diameter of ≥10 μm and ≤30 μm, the liquid particles are blown to the galvanized steel plate, and the wetting angle of the liquid particles with respect to the surface of the galvanized steel plate is ≤90°. COPYRIGHT: (C)2010,JPO&INPIT