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

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-a solid mass ratio [(Bs)/{(As)+(Bs)+(Cs)}], which is a ratio of solid mass content (Bs) of said cationic urethane resin emulsion (B) with respect to the total solid mass content {(As)+(Bs)+(Cs)} 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 [(Cs)/{(As)+(Bs)+(Cs)}], which is a ratio of solid mass content (Cs) of said silane coupling agent (C) with respect to the total solid mass content {(As)+(Bs)+(Cs)} 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 {(Cs)/(DTi)}, which is a ratio of solid mass content (Cs) of said silane coupling agent (C) with respect to mass content (DTi) in terms of titanium standard of said organic titanium chelate compound (D), is in the range of 50 to 70;
• (4) a mass ratio {(Ev)/(DTi)}, which is a ratio of mass content (Ev) in terms of vanadium standard of said quadrivalent vanadyl compound (E) with respect to mass content (DTi) 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 [(FMo)/{(As)+(Bs)+(Cs)}], which is a ratio of mass content (FMo) in terms of molybdenum standard of said molybdate compound (F) with respect to the total solid mass content {(As)+(Bs)+(Cs)} 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 [(GF)/{(As)+(Bs)+(Cs)}], which is a ratio of mass content (GF) in terms of fluorine standard of said fluorine compound (G) with respect to the total solid mass content {(As)+(Bs)+(Cs)} 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), Y1 and Y2 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), R1, R2, R3, R4, and R5 independently represent a hydrogen atom, a C1-C10 alkyl group, or a C1-C10 hydroxyalkyl group;
• and A− represents a hydroxide ion or an acid ion.