Surface treatment for metal, process for surface treatment of metallic substances, and surface-treated metallic substances

A surface treatment agent for metal, comprising water, at least one water-soluble resin or water-based emulsion resin (A) selected from the group consisting of cationic and nonionic urethane, acrylic, epoxy, polyester, and polyamide resins, a resin compound (B) represented by the general formula (I), and a metal compound (C) containing at least one metal selected from the group consisting of Zr, Ti, V, Mo, W, Mn, and Ce:

• 5
• wherein each R1 independently represents —CH2—, —CH2—NH—CH2—, or —CH═N—CH2—;
• Y represents a hydrogen atom or a group represented by the general formula (II)
• 6
• (wherein R2 and R3 independently represent a hydrogen atom or an alkyl group with 1 to 3 carbon atoms);
• Z is a bivalent group that is generated with the loss of hydrogen atoms bonded to carbon atoms constituting the aromatic ring from an aromatic compound that can undergo addition condensation with formaldehyde, may have 1 to 4 —CH2X groups (wherein X is OH, OR4 (R4 representing an alkyl group with 1 to 5 carbon atoms or a hydroxyalkyl group with 1 to 5 carbon atoms), a halogen atom, or a group represented by the general formula (III) or (IV)
• 7
• (wherein R5, R6, R7, R8 and R9 independently represent a hydrogen atom, an alkyl group with 1 to 10 carbon atoms, or a hydroxyalkyl group with 1 to 10 carbon atoms, and A− represents a hydroxyl ion or acid ion)), and differs from the aromatic ring group in the structure enclosed in brackets with subscript n, or a bivalent group generated with the loss of one hydrogen atom from each of two amino groups of melamine, guanamine, or urea;
• each W is independently hydrogen or a P group, said P group being —CH2X, —CH2NHCH2X, or —CH═NCH2X, the degree of substitution with said P groups satisfying the relationship:
• (number of P groups)/(total number of benzene rings and Z groups)=0.2 to 4.0, and the ratio:
• (number of —CH2X groups where X is a functional group represented by the formula (III) or (IV)+number of —CH2NHCH2X groups+number of —CH═NCH2X groups)/(total number of P groups) being 0.1 to 1.0;
• n is 0 or an integer of 1 to 29;
• and m is 0 or an integer of 1 to 10.