Surface treatment composition for metallic material and method for treatment

A composition of surface treatment agent used for metallic material, characterized by consisting essentially of the following components dissolved in a water-soluble medium:

• (A) a cationic component, which consists of divalent or higher valent metallic ions selected from the group consisting of manganese, cobalt, zinc, magnesium, nickel, iron, titanium, aluminum and zirconium;
• (B) at least one acid component selected from the group consisting of (1) fluoro-acid which contains four or more fluorine atoms, and one or more elements selected from the group consisting of titanium, zirconium, silicon, hafnium, aluminum and boron, and (2) acetic acid;
• (C) a silane coupling-agent component which consists of one or more compounds which contain at least one reactive functional group selected from an amino group containing active hydrogen, an epoxy group, a vinyl group, a mercapto group and a methacryloxy group;
• (D) one or more water-soluble polymer components which are expressed by the following general formula (I) and has a polymerization degree of from 2 to 50 of the polymeric unit,
• in the formula (I), X1 bonded to the benzene ring is hydrogen atom, a hydroxyl group, an alkyl group of C1 to C5, a hydroxylalkyl group of C1 to C10, aryl group of C6 to C12, a benzyl group, a benzal group, an unsaturated hydrocarbon group (formula II) which condenses with said benzene ring to form a naphthalene ring, or formula III;
• in the formula (II) X2 bonded to the benzene ring is hydrogen atom, a hydroxyl group, an aryl group of C6 to C12, a benzyl group and a benzal group,
• R1 and R2 in the formula (III) are, each or independently from one another, a hydrogen atom, a hydroxyl group, an alkyl group of C1 to C6 or a hydroxyalkyl group of C1 to C10, and Y1 and Y2 bonded to the benzene ring in the formula (I), (II) and (III) are a Z group expressed by the following formula (IV) and (V),
• in said formula (IV) and (V) R3, R4 R5, R6 and R7 are, each or independently from one another, a hydrogen atom, an alkyl group of C1 to C5 or a hydroxyalkyl group of C1 to C10, X1, Y1 and Y2 coupled to a benzene ring of said polymerization units may each be the same as or different from the X1, Y1 and Y2 coupled to the other benzene rings, and the value of substitution of said Z group in each benzene ring of said polymer molecules is from 0.2 to 1.0 in average.