Surface treatment liquid for zinc or zinc alloy coated steel sheet, zinc or zinc alloy-coated steel sheet, and method for manufacturing the same

1. A surface treatment liquid for a zinc or zinc alloy-coated steel sheet comprising:

(A) a resin compound having a bisphenol skeleton represented by general formula (I) below;

(B) a cationic urethane resin emulsion having at least one type of cationic functional group selected from the group consisting of primary to tertiary amino groups and a quaternary ammonium base;

(C) at least one type of silane coupling agent having at least one type of reactive functional group selected from the group consisting of active hydrogen-containing amino group, epoxy group, mercapto group, and methacryloxy group;

(D) an organic titanium chelate compound;

(E) a quadrivalent vanadyl compound;

(F) a molybdate compound;

(G) a fluorine compound; and

(H) water,

pH of said surface treatment liquid is in the range of 4 to 5, and

wherein the components satisfy the following conditions (1) to (6):

(1) a solid mass ratio [(B s )/{(A s )+(B s )+(C s )}], which is a ratio of solid mass content (B s ) of said cationic urethane resin emulsion (B) with respect to the total solid mass content {(A s )+(B s )+(C s )} of said resin compound (A), said cationic urethane resin emulsion (B), and said silane coupling agent (C), is in the range of 0.10 to 0.30;

(2) a solid mass ratio [(C s )/{(A s )+(B s )+(C s )}], which is a ratio of solid mass content (C s ) of said silane coupling agent (C) with respect to the total solid mass content {(A s )+(B s )+(C s )} of said resin compound (A), said cationic urethane resin emulsion (B), and said silane coupling agent (C), is in the range of 0.60 to 0.85;

(3) a mass ratio {(C s )/(D Ti )}, which is a ratio of solid mass content (C s ) of said silane coupling agent (C) with respect to mass content (D Ti ) in terms of titanium standard of said organic titanium chelate compound (D), is in the range of 50 to 70;

(4) a mass ratio {(E v )/(D Ti )}, which is a ratio of mass content (E v ) in terms of vanadium standard of said quadrivalent vanadyl compound (E) with respect to mass content (D Ti ) in terms of titanium standard of said organic titanium chelate compound (D), is in the range of 0.30 to 0.50;

(5) a mass ratio [(F Mo )/{(A s )+(B s )+(C s )}], which is a ratio of mass content (F Mo ) in terms of molybdenum standard of said molybdate compound (F) with respect to the total solid mass content {(A s )+(B s )+(C s )} of said resin compound (A), said cationic urethane resin emulsion (B), and said silane coupling agent (C), is in the range of 0.003 to 0.03; and

(6) a mass ratio [(G F )/{(A s )+(B s )+(C s )}], which is a ratio of mass content (G F ) in terms of fluorine standard of said fluorine compound (G) with respect to the total solid mass content {(A s )+(B s )+(C s )} of said resin compound (A), said cationic urethane resin emulsion (B), and said silane coupling agent (C), is in the range of 0.01 to 0.1;

wherein in general formula (I), Y 1 and Y 2 respectively bonded to benzene rings independently represent a hydrogen atom or a Z group represented by general formula (II) or (III) below; the average number of substituent Z groups per benzene ring is in the range of 0.2 to 1.0; and “n” is an integer in the range of 2 to 50;

and wherein in general formula (II) or (III), R 1 , R 2 , R 3 , R 4 , and R 5 independently represent a hydrogen atom, a C 1 -C 10 alkyl group, or a C 1 -C 10 hydroxyalkyl group; and A − represents a hydroxide ion or an acid ion.

2. The surface treatment liquid for a zinc or zinc alloy-coated steel sheet according to claim 1 , further comprising wax (W),

wherein a mass ratio [(W s )/{(A s )+(B s )}], which is a ratio of solid mass content (W s ) of the wax (W) with respect to the total solid mass content {(A s )+(B s )} of said resin compound (A) and said cationic urethane resin emulsion (B), is in the range of 0.2 to 0.4.

3. A method of manufacturing a zinc or zinc alloy-coated steel sheet, comprising the steps of:

applying the surface treatment liquid of claim 1 to a surface of the zinc or zinc alloy-coated steel sheet so that a coating amount after drying is in the range of 0.2 g/m 2 to 1.8 g/m 2 per surface; and

drying the zinc or zinc alloy-coated steel sheet at an ultimate sheet temperature in the range of 50 ° C. to 180 ° C.

4. A zinc or zinc alloy-coated steel sheet produced by the process of claim 3 .

5. A method of manufacturing a zinc or zinc alloy-coated steel sheet, comprising the steps of:

applying the surface treatment liquid of claim 2 to a surface of the zinc or zinc alloy-coated steel sheet so that a coating amount after drying is in the range of 0.2 g/m 2 to 1.8 g/m 2 per surface; and

drying the zinc or zinc alloy-coated steel sheet at an ultimate sheet temperature in the range of 50 ° C. to 180 ° C.

6. A zinc or zinc alloy-coated steel sheet produced by the process of claim 5 .