COMPOSITION FOR TREATING SURFACE OF METAL, METHOD FOR TREATING SURFACE OF METAL USING THE COMPOSITION, AND COATING FILM FOR TREATING SURFACE OF METAL UTILIZING THE COMPOSITION AND THE METHOD

摘要

Disclosed is a composition for treating the surface of a metal, which enables the formation of a coating film capable of imparting excellent corrosion resistance on a metal material, particularly a metal structure having a complex shape, in a single immersion step. Specifically disclosed is a composition for treating the surface of a metal, which is characterized by comprising 5 to 30% by weight of a nonionic and/or cationic aqueous resin, 100 to 1000 ppm of a trivalent Bi ion, and an aminopolycarboxylic acid in an amount of 0.5- to 10-fold mol concentration relative to the amount of the Bi ion.