| 摘要 |
A method is provided for forming a film having excellent anticorrosion properties on a metal surface without producing sludge, and without using phosphorus or chromium. In this method, the following steps (a)-(c) are performed on a metal material: (a) degreasing, (b-1) pretreatment if necessary, and (c) which comprises the following steps (c-1) or (c-2). The film-forming step (c-1) is a step for forming a film by bringing the metal material in contact with an aqueous solution comprising at least one of the following compositions (A), (B), (C) or (D): (A) is a monomer comprising a sulfonium group at one end of the molecule. (B) is a water-soluble polymer obtained by homopolymerization or copolymerization of the monomer (A). (C) is an emulsion or water-soluble polymer comprising a sulfonium group obtained by copolymerization of the monomer (A) and a radical-polymerizable unsaturated monomer excluding the monomer (A). (D) is a composite emulsion comprising a sulfonium group wherein inorganic particle core are coated by a layer comprising a copolymer of the aforesaid monomer (A) and a radical-polymerizable unsaturated monomer excluding the monomer (A). The film-forming step (c-2) is a step for forming a film by electrodeposition wherein the metal material is dipped in an aqueous solution comprising at least one of the above compositions (A), (B), (C), (D), and a current is passed between a cathode and an anode with the metal material as cathode.
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