JP2012062565A - Water-based surface treatment liquid for zinc-based plated steel sheet, and surface-treated zinc-based plated steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-based surface treatment liquid for a zinc-based plated steel sheet, which does not contain hexavalent chromium at all, and can obtain a surface-treated membrane which is excellent in conductivity, corrosion resistance and paint adhesion property; and to provide the surface-treated zinc-based plated steel sheet which does not contain hexavalent chromium in the membrane, and is excellent in conductivity, corrosion resistance and paint adhesion property.SOLUTION: The water-based surface treatment liquid contains, at a specified rate, a water-soluble zirconium compound, water diffusible fine particle silica, a silane coupling agent, a vanadate compound, a phosphate compound, a nickel compound and an acrylic resin emulsion. Furthermore, the surface-treated zinc-based plated steel sheet contains, on the surface of the zinc-based plated steel sheet at a specified rate, a zirconium compound, fine particle silica, a silane coupling agent derivative component, a vanadate compound, a phosphate compound, a nickel compound and an acrylic resin, and also has a surface-treated membrane in which a Zr adhesion amount is 10 to 200 mg/m.

Description

  The present invention relates to a surface treatment technology for a zinc-based plated steel sheet used for automobiles, home appliances, building materials, and the like, and specifically, an environment that does not contain any pollution-controlling substances such as hexavalent chromium in treatment liquids and coatings. The present invention relates to an aqueous surface treatment solution for a harmonized zinc-based plated steel sheet and a surface-treated zinc-based plated steel sheet.

  For steel plates for automobiles, steel plates for household appliances, and steel plates for building materials, hexavalent chromium has been used for the purpose of improving the corrosion resistance (white rust resistance, red rust resistance) on the surface of zinc-plated steel sheets or aluminum-plated steel sheets. Steel plates that have been subjected to chromate treatment with a treatment liquid containing as a main component have been widely used. However, in recent years, as a countermeasure against global environmental problems, surface-treated steel sheets with a surface-treated film that does not contain hexavalent chromium, which is a pollution-controlling substance, have come to be used in place of the conventionally used chromate treatment. For example, the following proposals have been made as a chromate-free treatment method for suppressing the white rust of zinc in a galvanized steel sheet.

  Patent Document 1 discloses a method of forming a film with a surface treatment liquid containing a vanadium compound, a titanium compound, or a zirconium compound. Patent Documents 2 and 3 disclose methods for forming a film containing a silane coupling agent in addition to the above compounds. Patent Documents 4 to 6 disclose methods for forming a film containing an organic resin together with a vanadium compound, a titanium compound, a zirconium compound, and a silane coupling agent.

JP 2008-63621 A JP 2007-177314 A JP 2008-133510 A JP 2007-204847 A JP 2007-162098 A JP 2007-152435 A JP 2008-169470 A

However, in the methods of Patent Document 1 and Patent Documents 2 and 3, since the content of the organic resin in the surface treatment film is less than several percent or does not include the organic resin, during film formation or handling, Cracks and the like are likely to occur in the film during processing, and sufficient corrosion resistance cannot be obtained. In addition, in the methods of Patent Documents 4 to 6, by containing an organic resin, a decrease in corrosion resistance due to cracks can be suppressed and deterioration of corrosion resistance can be prevented, but there is no effect of greatly improving corrosion resistance. Moreover, since it is necessary to ensure a certain level of film thickness in order to develop corrosion resistance, there is a problem that it is impossible to achieve both conductivity.
Patent Document 7 discloses a technique for forming a film made of a zirconium compound, a silane coupling agent, silica, and an organic resin. Although this technology can provide a film with an excellent appearance even after press molding, the content of the organic resin and the film thickness are limited in order to develop an excellent appearance, so in applications that do not require press molding Corrosion resistance was not always sufficient.

As described above, although the film mainly composed of a zirconium compound or a silane coupling agent exhibits corrosion resistance to some extent, the technology for obtaining a film having excellent performance in all of conductivity, corrosion resistance, and paint adhesion is Not yet proposed.
Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art and to obtain a surface-treated film having excellent conductivity, corrosion resistance, and paint adhesion without containing hexavalent chromium at all. An object of the present invention is to provide an aqueous surface treatment solution for a plated steel sheet.
Another object of the present invention is to provide a method for producing a surface-treated galvanized steel sheet using this aqueous surface treatment liquid.
Furthermore, another object of the present invention is to provide a surface-treated zinc-based plated steel sheet that has excellent conductivity, corrosion resistance, and paint adhesion without containing hexavalent chromium in the film.

The gist of the present invention for solving such problems is as follows.
[1] Water-soluble zirconium compound (A), water-dispersible fine particle silica (B), silane coupling agent (C), vanadic acid compound (D), phosphoric acid compound (E), nickel compound ( F) and an acrylic resin emulsion (G) so as to satisfy the following conditions (1) to (7): An aqueous surface treatment solution for galvanized steel sheets.
(1) Mass ratio (B) / (A) = 0.1 to 1.2 of water-dispersible fine particle silica (B) and Zr equivalent amount of water-soluble zirconium compound (A)
(2) Mass ratio of silane coupling agent (C) to water-soluble zirconium compound (A) in terms of Zr (C) / (A) = 0.5 to 3.0
(3) Mass ratio (D) / (A) = 0.02 to 0.15 of V converted amount of vanadic acid compound (D) and Zr converted amount of water-soluble zirconium compound (A)
(4) Mass ratio (E) / (A) = 0.03 to 0.30 of P equivalent of phosphoric acid compound (E) and Zr equivalent of water-soluble zirconium compound (A)
(5) Mass ratio (F) / (A) = 0.005 to 0.10 of Ni conversion amount of nickel compound (F) and Zr conversion amount of water-soluble zirconium compound (A)
(6) Mass ratio (SI) / (A) of the total amount (SI) of Si equivalents of the water-dispersible fine particle silica (B) and the silane coupling agent (C) and the Zr equivalent amount of the water-soluble zirconium compound (A) ) = 0.15 to 1.0
(7) Mass ratio (G) / (X) = 0.18 to 0.75 between the solid content of the acrylic resin emulsion (G) and the total amount (X) of the solid content in the aqueous surface treatment liquid

[2] The aqueous surface treatment solution for galvanized steel sheet according to [1], further comprising a wax (H) so as to satisfy the following condition (8):
(8) Mass ratio (H) / (X) = 0.01-0.10 of solid content of wax (H) and total amount (X) of solid content in aqueous surface treatment liquid
[3] The aqueous surface treatment solution according to the above [1] or [2] is applied to the surface of a galvanized steel sheet so that the Zr adhesion amount is 10 to 200 mg / m ² and dried. A method for producing a surface-treated zinc-based plated steel sheet.

[4] On the surface of the galvanized steel sheet, zirconium compound (a), fine particle silica (b), silane coupling agent-derived component (c), vanadic acid compound (d), and phosphoric acid compound (e) And a nickel compound (f) and an acrylic resin (g) so as to satisfy the following conditions (1) to (6), and having a surface treatment film having a Zr adhesion amount of 10 to 200 mg / m ^2. A surface-treated zinc-based plated steel sheet.
(1) Mass ratio (b) / (a) = 0.1 to 1.2 of fine particle silica (b) and Zr equivalent amount of zirconium compound (a)
(2) Mass ratio (Si) / (a) = 0 of the total amount (Si) of Si in the fine particle silica (b) and the silane coupling agent-derived component (c) and the amount of Zr in the zirconium compound (a) .15-1.0
(3) Mass ratio (d) / (a) = 0.02 to 0.15 of V converted amount of vanadic acid compound (d) and Zr converted amount of zirconium compound (a)
(4) Mass ratio (e) / (a) = 0.03 to 0.30 of P equivalent of phosphoric acid compound (e) and Zr equivalent of zirconium compound (a)
(5) The mass ratio (f) / (a) between the Ni conversion amount of the nickel compound (f) and the Zr conversion amount of the zirconium compound (a) is 0.005 to 0.10.
(6) Mass ratio (g) / (x) = 0.18 to 0.75 between the acrylic resin (g) and the total amount (x) of the solid content of the film
[5] The surface-treated zinc-based steel sheet according to [4], wherein the surface-treated film further contains a wax (h) so as to satisfy the following condition (7): Plated steel sheet.
(7) Mass ratio (h) / (x) = 0.01-0.10 of wax (h) and total amount (x) of film solids

  The aqueous surface treatment liquid for galvanized steel sheet according to the present invention can obtain a surface treatment film having excellent conductivity, corrosion resistance, and paint adhesion without containing hexavalent chromium at all. According to the production method of the present invention using a liquid, a surface-treated zinc-based plated steel sheet having excellent conductivity, corrosion resistance, and paint adhesion can be produced without containing hexavalent chromium in the film. Further, the surface-treated zinc-based plated steel sheet of the present invention has excellent conductivity, corrosion resistance, and paint adhesion without containing hexavalent chromium in the film. For this reason, it is suitable as a surface-treated zinc-based plated steel sheet used for automobiles, home appliances, OA equipment and the like.

The details of the present invention and the reasons for limitation will be described below.
The zinc-based plated steel sheet used as the base of the surface-treated steel sheet of the present invention may be any zinc-containing plated steel sheet that contains zinc in the plating film, such as a zinc-plated steel sheet, a Zn-Ni alloy-plated steel sheet, and a Zn-Al alloy-plated steel sheet. (E.g., Zn-5 mass% Al alloy plated steel sheet, Zn-55 mass% Al alloy plated steel sheet), Zn-Al-Mg alloy plated steel sheet (e.g., Zn-6 mass% Al-3 mass% Mg alloy plated steel sheet, Zn-11 mass%) Al-3 mass% Mg alloy-plated steel sheet) can be mentioned, but is not limited thereto.
In addition, a small amount of different metal elements or impurities such as nickel, cobalt, manganese, iron, molybdenum, tungsten, titanium, chromium, aluminum, magnesium, lead, antimony, tin, copper etc. A plated steel sheet containing two or more seeds can also be used. In addition, among the above-described plating, a multi-layer plated steel sheet in which two or more layers of the same type or different types are plated can also be used.

First, the aqueous surface treatment solution for galvanized steel sheet according to the present invention will be described.
This aqueous surface treatment liquid uses water as a solvent, a water-soluble zirconium compound (A), a water-dispersible fine particle silica (B), a silane coupling agent (C), a vanadate compound (D), and phosphoric acid. It contains a compound (E), a nickel compound (F), and an acrylic resin emulsion (G), and preferably contains these components (A) to (G) as main components. This aqueous surface treatment liquid does not contain hexavalent chromium. Moreover, this aqueous surface treatment liquid can contain a wax (H) further as needed.

  The water-soluble zirconium compound (A) is not particularly limited, and examples thereof include zirconium nitrate, zirconium oxynitrate, zirconyl acetate, zirconyl sulfate, zirconyl ammonium carbonate, zirconyl potassium carbonate, and zirconyl sodium carbonate. One or more types can be used. Here, even when an inorganic fluorine-containing compound such as zircon hydrofluoric acid or a salt thereof is included, it is a water-soluble zirconium compound and can be used as long as the solution is compatible. Since silica is contained as an essential component, the liquid stability is often impaired when an inorganic fluorine-containing compound is contained, and therefore zircon hydrofluoric acid and its salt are not so preferable.

The water-dispersible fine particle silica (B) is not particularly limited in particle size or type, but colloidal silica or dry silica can be used. Examples of colloidal silica include Snowtex O, C, N, 20, OS, OXS (all trade names) manufactured by Nissan Chemical Co., Ltd., and examples of dry silica include Nippon Aerosil Co., Ltd. AEROSIL50, 130, 200, 300, and 380 (all are brand names) manufactured by the company etc. are mentioned, These 1 or more types can be used.
The mixing ratio of the water-dispersible fine particle silica (B) is 0.1 to 1 in mass ratio (B) / (A) between the water-dispersible fine particle silica (B) and the Zr equivalent amount of the water-soluble zirconium compound (A). .2. If (B) / (A) is less than 0.1, the conductivity and paint adhesion will be reduced. On the other hand, if the mass ratio (B) / (A) exceeds 1.2, the coating cannot be formed properly, so that the corrosion resistance is low. descend. From such a viewpoint, the more preferable mass ratio (B) / (A) is 0.2 to 1.0, and particularly preferably 0.3 to 0.8.

  Examples of the silane coupling agent (C) include vinyl methoxy silane, vinyl ethoxy silane, vinyl trichloro silane, vinyl trimethoxy silane, vinyl triethoxy silane, β- (3,4 epoxy cyclohexyl) ethyl trimethoxy silane, γ -Glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (amino Ethyl) γ-aminopropylmethyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyltrimethoxysilane, γ-methacryloxy Propylmethyldiethoxysilane, γ-methacryloxypropylmethyltriethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropylmethyltrimethoxysilane, p-styryltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, γ-chloropropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, γ-isocyanatopropyltriethoxysilane, γ-triethoxy Cisilyl-N- (1,3-dimethyl-butylidene) propylamine, N- (vinylbenzylamine) -β-aminoethyl-γ-aminopropyltrimethoxysilane, and the like, and one or more of these should be used Can do.

  The mixing ratio of the silane coupling agent (C) is 0.5 to 3.0 in terms of a mass ratio (C) / (A) between the silane coupling agent (C) and the Zr equivalent amount of the water-soluble zirconium compound (A). And When the mass ratio (C) / (A) is less than 0.5, the conductivity and paint adhesion are reduced. On the other hand, when it exceeds 3.0, the coating cannot be formed properly, so that the corrosion resistance is reduced. Stability is also reduced. From such a viewpoint, the more preferable mass ratio (C) / (A) is 1.0 to 2.5, and particularly preferably 1.2 to 2.0.

Examples of the vanadic acid compound (D) include ammonium metavanadate and sodium metavanadate, and one or more of these can be used. Here, V of the vanadic acid compound is pentavalent, but the corrosion resistance and conductivity cannot be sufficiently ensured with the tetravalent vanadium compound.
The compounding ratio of the vanadic acid compound (D) is 0.02 to 0 in mass ratio (D) / (A) of the V converted amount of the vanadic acid compound (D) and the Zr converted amount of the water-soluble zirconium compound (A). .15. When the mass ratio (D) / (A) is less than 0.02, the corrosion resistance is lowered. On the other hand, when it exceeds 0.15, the film is colored, the appearance is deteriorated and the blackening resistance is lowered. From such a viewpoint, the more preferable mass ratio (D) / (A) is 0.04 to 0.12, and particularly preferably 0.05 to 0.10.

The phosphoric acid compound (E) is not particularly limited as long as it is compatible with the liquid. Examples of the phosphoric acid compound include phosphoric acid, primary phosphate, secondary phosphate, and tertiary phosphate. Salt, pyrophosphate, pyrophosphate, tripolyphosphate, condensed polyphosphate such as tripolyphosphate, phosphorous acid, phosphite, hypophosphorous acid, hypophosphite, phosphonic acid, phosphonate Can be mentioned. Examples of the phosphonate include nitrilotrismethylenephosphonic acid, phosphonobutanetricarboxylic acid, ethylenediaminetetramethylenephosphonic acid, methyldiphosphonic acid, methylenephosphonic acid, ethylidenediphosphonic acid, and ammonium salts and alkali metal salts thereof. Etc. One or more of these phosphoric acid compounds can be used.
The mixing ratio of the phosphoric acid compound (E) is 0.03 to 0 in mass ratio (E) / (A) between the P equivalent amount of the phosphoric acid compound (E) and the Zr equivalent amount of the water-soluble zirconium compound (A). .30. When the mass ratio (E) / (A) is less than 0.03, the corrosion resistance is lowered. On the other hand, when it exceeds 0.30, the appearance and blackening resistance of the film are lowered. From such a viewpoint, the more preferable mass ratio (E) / (A) is 0.06 to 0.20, and particularly preferably 0.10 to 0.18.

The nickel compound (F) is not particularly limited as long as it is compatible with the liquid, and examples thereof include nickel nitrate, nickel sulfate, nickel carbonate, nickel chloride, nickel phosphate, and one or more of these. Can be used.
The mixing ratio of the nickel compound (F) is 0.005 to 0.10 in mass ratio (F) / (A) between the Ni conversion amount of the nickel compound (F) and the Zr conversion amount of the water-soluble zirconium compound (A). And When the mass ratio (F) / (A) is less than 0.005, the blackening resistance decreases, whereas when it exceeds 0.10, the corrosion resistance decreases. From such a viewpoint, (F) / (A) is more preferably 0.01 to 0.08, and particularly preferably 0.02 to 0.06.
The sum (SI) of the Si-converted amount of the water-dispersible fine particle silica (B) and the silane coupling agent (C) is the mass ratio (SI) / (A) with the Zr-converted amount of the water-soluble zirconium compound (A). 0.15-1.0. When the mass ratio (SI) / (A) is less than 0.15, the conductivity and paint adhesion are deteriorated. On the other hand, when it exceeds 1.0, the corrosion resistance is deteriorated. From such a viewpoint, the more preferable mass ratio (SI) / (A) is 0.25 to 0.85, and particularly preferably 0.30 to 0.68.

The acrylic resin emulsion (G) is an aqueous emulsion resin obtained by emulsion polymerization of vinyl monomers such as acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, and styrene. Although there is no restriction | limiting in particular in a kind, Especially, a nonionic emulsifier can be applied suitably. Among nonionic emulsifiers, those having a structure having polyethylene oxide or polypropylene oxide can be particularly suitably applied.
The blending ratio of the acrylic resin emulsion (G) is 0.18 in mass ratio (G) / (X) of the solid content of the acrylic resin emulsion (G) and the total amount (X) of the solid content in the aqueous surface treatment liquid. Super to 0.75. When the mass ratio (G) / (X) is 0.18 or less, the paint adhesion decreases, whereas when it exceeds 0.75, the corrosion resistance decreases. From such a viewpoint, a more preferable mass ratio (G) / (X) is 0.2 to 0.6, and particularly preferably 0.25 to 0.5.

The acrylic resin constituting the acrylic resin emulsion (G) preferably has a glass transition temperature (Tg) calculated by the following formula (1) of 10 to 30 ° C. The following equation (1) is generally called a FOX equation.
1 / Tg = Σ (Wi / Tgi) (1)
When the Tg of the acrylic resin is less than 10 ° C., the appearance after press molding is lowered, whereas when the Tg exceeds 30 ° C., the corrosion resistance tends to be lowered.

Wax (H) can be added to the aqueous surface treatment liquid of the present invention in order to improve the lubricating performance during continuous press molding.
The wax (H) is not particularly limited as long as it is compatible with the liquid. For example, polyolefin wax such as polyethylene, montan wax, paraffin wax, microcrystalline wax, carnauba wax, lanolin wax, silicon wax , Fluorine wax, and the like, and one or more of these can be used. Examples of the polyolefin wax include polyethylene wax, polyethylene oxide wax, and polypropylene wax, and one or more of these can be used.
The blending ratio of the wax (H) is 0.01 to 0.10 in mass ratio (H) / (X) of the solid content of the wax (H) and the total amount (X) of the solid content in the aqueous surface treatment liquid. It is preferable that When the mass ratio (H) / (X) is less than 0.01, no effect of improving lubricity, particularly the lubricity during press molding, is observed. On the other hand, when it exceeds 0.10, the adhesion of the paint decreases and the corrosion resistance. May also decrease. From such a viewpoint, a more preferable mass ratio (H) / (X) is 0.02 to 0.08.

  The pH of the aqueous surface treatment liquid of the present invention is not particularly limited, but is preferably pH 6 to 11 and more preferably pH 8 to 10 from the viewpoint of the stability of the treatment liquid. When the pH of the treatment liquid is less than 6, the stability of the treatment liquid is lowered, and the corrosion resistance and the appearance of the film are lowered. On the other hand, when the pH exceeds 11, the etching of zinc becomes remarkable, the appearance of the film is also lowered, and the conductivity tends to be lowered. As the alkali used for adjusting the pH, ammonia and amine are preferable, and as the acid, a phosphoric acid compound is preferable.

The water-based surface treatment liquid as described above is applied to the surface of the zinc-based plated steel sheet and heat-dried to form a surface-treated film. The adhesion amount of the surface-treated film after heat drying is preferably 10 to ²⁰⁰ mg / m ^{2 in} terms of Zr equivalent of the zirconium compound in the film. If the adhesion amount is less than 10 mg / m ² , sufficient corrosion resistance cannot be obtained. On the other hand, if it exceeds 200 mg / m ² , the film is thick and the conductivity is lowered. From such a viewpoint, the more preferable adhesion amount is 20 to 180 mg / m ² , and particularly preferably 30 to 150 mg / m ² .
Further, the thickness of the surface treatment film after heat drying is not particularly limited as long as the Zr adhesion amount falls within the above range, but after ensuring the blending ratio of each component and the Zr adhesion amount range. Therefore, the thickness is preferably 1.0 μm or less. If the film thickness exceeds 1.0 μm, the conductivity may decrease. From such a viewpoint, a more preferable film thickness is 0.8 μm or less, and more preferably 0.5 μm or less.

As a method for forming a surface treatment film by applying an aqueous surface treatment liquid to the surface of a zinc-based plated steel sheet, a commonly used method may be used. For example, the surface of the galvanized steel sheet is treated with a water-based surface treatment solution by a coating method, a dipping method, or a spray method, and then dried by heating. As a coating method, any method such as a roll coater (for example, a 3-roll system, a 2-roll system), a squeeze coater, a bar coater, or a spray coater may be used. In addition, after the coating process using a squeeze coater or the like, or the dipping process or the spray process, the coating amount may be adjusted, the appearance may be made uniform, or the film thickness may be made uniform by an air knife method or a roll drawing method.
The heating means for performing heat drying is not particularly limited, and a dryer, a hot air furnace, a high frequency induction heating furnace, an infrared furnace, or the like can be used. The heating and drying temperature is preferably 50 to 250 ° C. as the ultimate plate temperature. If it exceeds 250 ° C., cracks may occur in the coating and the corrosion resistance may be reduced. On the other hand, when the temperature is lower than 50 ° C., the moisture remaining in the film increases, and the corrosion resistance may also decrease. From such a viewpoint, a more preferable heating and drying temperature is 60 to 200 ° C, and particularly preferably 60 to 180 ° C.

Next, the surface-treated zinc-based plated steel sheet of the present invention obtained using the above water-based surface treatment liquid will be described.
This surface-treated zinc-based plated steel sheet has a zirconium compound (a), fine-particle silica (b), a silane coupling agent-derived component (c), a vanadate compound (d), on the surface of the zinc-based plated steel sheet, It has a surface treatment film containing a phosphoric acid compound (e), a nickel compound (f), and an acrylic resin (g), preferably containing these as the main components. This surface treatment film does not contain hexavalent chromium. Moreover, you may mix | blend wax (h) with this surface treatment film | membrane further as needed.

The zirconium compound (a) is a component derived from Zr in the water-soluble zirconium compound (A) blended in the treatment liquid, and details of the water-soluble zirconium compound (A) are as described above.
The fine particle silica (b) is derived from the water dispersible fine particle silica (B) blended in the treatment liquid, and details of the water dispersible fine particle silica (B) are as described above.
The content ratio of the fine particle silica (b) in the film is 0.1 to 1.2 in terms of the mass ratio (b) / (a) between the fine particle silica (b) and the Zr equivalent amount of the zirconium compound (a). . If (b) / (a) is less than 0.1, the conductivity and paint adhesion are reduced, while if the mass ratio (b) / (a) exceeds 1.2, the coating cannot be formed properly and corrosion resistance is reduced. descend. From such a viewpoint, the more preferable mass ratio (b) / (a) is 0.2 to 1.0, and particularly preferably 0.3 to 0.8.

The component (c) derived from the silane coupling agent is derived from the silane coupling agent (C) blended in the treatment liquid, and details of the silane coupling agent (C) are as described above.
Here, the sum (Si) of the Si equivalent amount of the particulate silica (b) and the silane coupling agent-derived component (c) is the mass ratio (Si) / (a) with the Zr equivalent amount of the zirconium compound (a). 0.15-1.0. When the mass ratio (Si) / (a) is less than 0.15, the conductivity and paint adhesion are deteriorated. On the other hand, when it exceeds 1.0, the corrosion resistance is deteriorated. From such a viewpoint, the more preferable mass ratio (Si) / (a) is 0.25 to 0.85, and particularly preferably 0.30 to 0.68.

The vanadic acid compound (d) is derived from the vanadic acid compound (D) blended in the treatment liquid, and details of the vanadic acid compound (D) are as described above.
The content ratio of the vanadic acid compound (d) in the film was 0.02 in terms of the mass ratio (d) / (a) of the V converted amount of the vanadic acid compound (d) and the Zr converted amount of the zirconium compound (a). To 0.15. When the mass ratio (d) / (a) is less than 0.02, the corrosion resistance is lowered. On the other hand, when it exceeds 0.15, the film is colored, the appearance is deteriorated and the blackening resistance is lowered. From such a viewpoint, the more preferable mass ratio (d) / (a) is 0.04 to 0.12, and particularly preferably 0.05 to 0.10.

The phosphoric acid compound (e) is derived from the phosphoric acid compound (E) blended in the treatment liquid, and details of the phosphoric acid compound (E) are as described above.
The content ratio of the phosphoric acid compound (e) in the film was 0.03 in mass ratio (e) / (a) between the P equivalent amount of the phosphoric acid compound (e) and the Zr equivalent amount of the zirconium compound (a). ~ 0.30. When the mass ratio (e) / (a) is less than 0.03, the corrosion resistance is lowered. On the other hand, when it exceeds 0.30, the appearance and blackening resistance of the film are lowered. From such a viewpoint, the more preferable mass ratio (e) / (a) is 0.06 to 0.20, and particularly preferably 0.10 to 0.18.

The nickel compound (f) is derived from the nickel compound (F) blended in the treatment liquid, and details of the nickel compound (F) are as described above.
The content ratio of the nickel compound (f) in the film is 0.005 to 0 in mass ratio (f) / (a) between the Ni conversion amount of the nickel compound (f) and the Zr conversion amount of the zirconium compound (a). .10. When the mass ratio (f) / (a) is less than 0.005, blackening resistance decreases, whereas when it exceeds 0.10, corrosion resistance decreases. From such a viewpoint, (f) / (a) is more preferably 0.01 to 0.08, and particularly preferably 0.02 to 0.06.

The acrylic resin (g) is derived from the acrylic resin emulsion (G) blended in the treatment liquid, and the details of the acrylic resin emulsion (G) and the acrylic resin are as described above.
The content ratio of the acrylic resin (g) in the film is more than 0.18 to 0.75 in mass ratio (g) / (x) of the acrylic resin (g) and the total amount (x) of the film solid content. To do. When the mass ratio (g) / (x) is 0.18 or less, the paint adhesion decreases, whereas when it exceeds 0.75, the corrosion resistance decreases. From such a viewpoint, the more preferable mass ratio (g) / (x) is 0.2 to 0.6, and particularly preferably 0.25 to 0.5.

The surface treatment film may further contain a wax (h) in order to improve the lubricating performance during continuous press molding. The wax (h) is derived from the wax (H) blended in the treatment liquid, and details of the wax (H) are as described above.
The content ratio of the wax (h) in the film may be 0.01 to 0.10 in mass ratio (h) / (x) between the wax (h) and the total amount (x) of the film solids. preferable. When the mass ratio (h) / (x) is less than 0.01, lubricity, in particular, the lubricity improvement effect during continuous press molding is not seen, while when it exceeds 0.10, the paint adhesion decreases, Corrosion resistance may also decrease. From such a viewpoint, a more preferable mass ratio (h) / (x) is 0.02 to 0.08.
As mentioned above, the adhesion amount of the surface treatment film is 10 to 200 mg / m ² , preferably 20 to 180 mg / m ² , more preferably 30 to 150 mg / m ^{2 in} terms of Zr of the zirconium compound in the film. And Similarly, the thickness of the surface treatment film is 1.0 μm or less, more preferably 0.8 μm or less, and further preferably 0.6 μm or less.

In the surface-treated zinc-based plated steel sheet obtained by the present invention, the reason why excellent conductivity, corrosion resistance and paint adhesion can be obtained is not necessarily clear, but is considered to be due to the following mechanism.
First, a film skeleton is formed by a water-soluble zirconium compound, water-dispersible fine particle silica, and a silane coupling agent. The water-dispersible fine particle silica is considered to maintain its shape even in the dried film. Moreover, when a silane coupling agent is dissolved in water, silanol and alcohol are produced by hydrolysis. The resulting silanol is dehydrated and condensed into polysiloxane. This polysiloxane is considered to be dispersed in water in a double structure with the core as the core and an alkyl group on the outside.

  In water-solubility, these double-structured zirconium compounds with fine silica and polysiloxane work as binders and penetrate between the double-structure with fine silica (particles) and polysiloxane, linking the dried film. To form a film. The inorganic film formed in this way is easily damaged during handling, and is easily crushed by the stress during press molding, so that it is difficult to obtain the corrosion resistance of the cracked portion. However, by blending an appropriate amount of a specific resin (acrylic resin) into the film, it can function as a binder in the film as well as the water-soluble zirconium compound, and can relieve the stress applied to the film, thus providing stable corrosion resistance. Can do.

  As mentioned above, water-soluble zirconium compound, water-dispersible fine particle silica, silane coupling agent and acrylic resin are components that form the skeleton of the film, and once dried, do not dissolve in water again and have a barrier effect. It is done. On the other hand, the vanadic acid compound and the phosphoric acid compound are uniformly dispersed in the film and exist in a form that is easily soluble in water, and have an inhibitory effect during so-called zinc corrosion. That is, the vanadic acid compound suppresses the corrosion of zinc itself by a passivating action, and the phosphoric acid compound etches zinc when coming into contact with zinc to form a slightly soluble metal salt with dissolved zinc, or When zinc corrosion occurs, it is considered that zinc ions are trapped in the film and further corrosion is suppressed. Thus, it is possible to obtain excellent corrosion resistance by using together inhibitors having different corrosion inhibition mechanisms. In addition, when an acrylic resin is blended, the effect of suppressing the elution of vanadic acid compound and phosphoric acid compound into water is exhibited, so that the paint adhesion is not deteriorated even after immersion in boiling water for 2 hours. It is thought that it has.

  Since this surface-treated film does not have conductivity in the film itself, it is considered that conductivity develops at the convex portion of the steel sheet surface where the film is locally thin. The aqueous surface treatment liquid of the present invention preferably has a pH of 6 to 11 from the viewpoint of the stability of the treatment liquid. However, since the etching of zinc is a mild region, the protrusions of the zinc-based plated steel sheet undergo significant etching. Compared to the above, it is presumed that the reaction is less likely to occur and it is easy to form a thin film, which is one of the causes of excellent conductivity.

Water-soluble zirconium compound shown in Table 2, water-dispersed fine particle silica shown in Table 3, silane coupling agent shown in Table 4, vanadic acid compound shown in Table 5, phosphate compound shown in Table 6, nickel compound shown in Table 7, Using the acrylic resin emulsion (nonionic acrylic resin emulsion) shown in Table 8 and the wax shown in Table 9, these components were appropriately blended in water to prepare aqueous surface treatment liquids shown in Tables 10 to 13. The pH of the treatment liquid was appropriately adjusted with ammonia and phosphoric acid.
After the zinc-based plated steel sheet shown in Table 1 as the processing original plate is subjected to alkaline degreasing treatment, washed with water and dried, the aqueous surface treatment liquid is applied with a bar coater, and then the steel sheet surface temperature is a predetermined temperature within a few seconds to a few tens of seconds. It was dried by heating to form a surface treatment film. The film thickness of the surface treatment film was adjusted by the concentration of the aqueous surface treatment solution, and the Zr adhesion amount of the film was determined by quantifying Zr with a fluorescent X-ray analyzer.

Film thickness measurement is focused ion beam (Focused
A cross-section sample was prepared using an Ion Beam (FIB) processing apparatus (“FB2000A” manufactured by Hitachi, Ltd.) and an attached microsampling apparatus, and then was performed using a transmission electron microscope (TEM). Prior to FIB processing, a carbon (C) protective film is flash-deposited on the surface of the surface-treated steel sheet specimen for preparing a cross-section sample to a thickness of about 200 nm in order to protect it from damage caused by ion beam irradiation. Further, a protective film of gold (Au) was sputter coated thereon. After setting the test material with the surface protected in this manner to the FIB processing apparatus, the chemical vapor deposition (CVD) mechanism of the FIB processing apparatus is further used at the sampling position of the cross-sectional sample. A carbon protective film having a thickness of about 500 nm was coated, and a cross-sectional sample was cut out by an ion beam. A cross-sectional sample (about 20 μm in the width direction and about 10 μm in the depth direction) taken out using a micro-sampling device is fixed to a straight portion of a molybdenum meniscus-like special mesh using a CVD mechanism and then cut out by an ion beam. To a thickness suitable for TEM observation (about 0.1 μmt). Thereafter, the cross-sectional sample was observed with a TEM at an accelerating voltage of 200 kV, and the film thickness at three locations was measured in the range of about 10 μm, and the average value was taken as the film thickness.

  The quality performance (conductivity, corrosion resistance, paint adhesion, blackening resistance) of the obtained surface-treated zinc-based plated steel sheet was evaluated by the following methods. The results are shown in Tables 14 to 18 together with the manufacturing conditions and the film configuration. In addition, in the film | membrane structure of the surface treatment zinc-plated steel plate shown in Table 14-Table 18, mass ratio (b) / (a) of fine particle silica (b) and Zr conversion amount of a zirconium compound (a), vanadate compound (D) Mass ratio (d) / (a) of V conversion amount of zirconium compound (a) and Zr conversion amount of zirconium compound (a), P conversion amount of phosphoric acid compound (e) and Zr conversion amount of zirconium compound (a) Mass ratio (e) / (a), mass ratio (f) / (a) of Ni conversion amount of nickel compound (f) and Zr conversion amount of zirconium compound (a), acrylic resin (g), and coating solid For the mass ratio (g) / (x) to the total amount (x) of the minute and the mass ratio (h) / (x) of the total amount (x) of the wax (h) to the coating solids, see Table 10 Mass ratio (B) / (A), mass ratio (D) / (of composition of aqueous surface treatment liquid shown in Table 13 ), Mass ratio (E) / (A), (F) / (A), mass ratio (G) / (X), and mass ratio (H) / (X), respectively. 18 was not described.

(1) Conductivity Using a resistance measuring device (Loresta GP, ASP probe made by Dia Instruments), measuring the surface resistance of the steel sheet at 10 locations in a state where the pressing load of the ASP probe (4 probes) on the steel sheet surface is 200 g. The average value was evaluated. The evaluation criteria are as follows.
◎: Less than 0.1 mΩ ○: 0.1 mΩ or more, less than 1.0 mΩ ○-: 1.0 mΩ or more, less than 10.0 mΩ Δ: 10.0 mΩ or more, less than 100 mΩ ×: 100 mΩ or more

(2) Corrosion resistance About each sample, the salt spray test (JIS-Z-2371) was given in the state of the flat plate, and it evaluated by the white rust resistance after 168 hours. The evaluation criteria are as follows.
◎: White rust area ratio less than 5% ○: White rust area ratio 5% or more and less than 10% ○-: White rust area ratio 10% or more and less than 25% △: White rust area ratio 25% or more and less than 50% × : White rust area ratio 50% or more In addition, "corrosion resistance" of Table 18 showed the time (12-hour unit) when the white rust incidence rate in a salt spray test became 5% or more. In this corrosion resistance evaluation, 72 hours or more was regarded as acceptable.

(3) Paint adhesion For each sample, after applying a melamine-based baking paint (film thickness of 30 μm), it was immersed in boiling water for 2 hours, and immediately cut in a grid pattern (10 × 10, 1 mm interval). Peeling with cellophane was performed. The evaluation criteria are as follows.
◎: No peeling ○: Peeling area rate less than 5% △: Peeling area rate of 5% or more and less than 20%

(4) Blackening resistance Color difference ΔL ^* before and after holding the sample at 80 ° C. and 98% RH for 24 hours ΔL ^* (L ^* , a ^* , b ^* of the two object colors specified in JIS-Z-8729 CIE 1976 brightness L * difference) and visual evaluation. The evaluation criteria are as follows.
A: [0 ≦ ΔL ^* <1] and uniform appearance without unevenness ○: [-1 <ΔL ^* <0] and uniform appearance without unevenness ○ −: [−2 < ΔL ^* ≦ −1] and uniform appearance without unevenness Δ: [ΔL ^* ≦ −2] and uniform appearance without unevenness ×: Outstanding appearance of unevenness According to Tables 14 to 18 It can be seen that the inventive examples have good conductivity, corrosion resistance and paint adhesion, and are excellent in blackening resistance. On the other hand, in the comparative example, any one or more of conductivity, corrosion resistance, and paint adhesion is inferior.

Claims (5)

Water-soluble zirconium compound (A), water-dispersible fine particle silica (B), silane coupling agent (C), vanadic acid compound (D), phosphoric acid compound (E), nickel compound (F), A water-based surface treatment solution for a zinc-based plated steel sheet, comprising the acrylic resin emulsion (G) so as to satisfy the following conditions (1) to (7):
(1) Mass ratio (B) / (A) = 0.1 to 1.2 of water-dispersible fine particle silica (B) and Zr equivalent amount of water-soluble zirconium compound (A)
(2) Mass ratio of silane coupling agent (C) to water-soluble zirconium compound (A) in terms of Zr (C) / (A) = 0.5 to 3.0
(3) Mass ratio (D) / (A) = 0.02 to 0.15 of V converted amount of vanadic acid compound (D) and Zr converted amount of water-soluble zirconium compound (A)
(4) Mass ratio (E) / (A) = 0.03 to 0.30 of P equivalent of phosphoric acid compound (E) and Zr equivalent of water-soluble zirconium compound (A)
(5) Mass ratio (F) / (A) = 0.005 to 0.10 of Ni conversion amount of nickel compound (F) and Zr conversion amount of water-soluble zirconium compound (A)
(6) Mass ratio (SI) / (A) of the total amount (SI) of Si equivalents of the water-dispersible fine particle silica (B) and the silane coupling agent (C) and the Zr equivalent amount of the water-soluble zirconium compound (A) ) = 0.15 to 1.0
(7) Mass ratio (G) / (X) = 0.18 to 0.75 between the solid content of the acrylic resin emulsion (G) and the total amount (X) of the solid content in the aqueous surface treatment liquid Furthermore, wax (H) is included so that the conditions of following (8) may be satisfied, The aqueous surface treatment liquid for galvanized steel sheets of Claim 1 characterized by the above-mentioned.
(8) Mass ratio (H) / (X) = 0.01-0.10 of solid content of wax (H) and total amount (X) of solid content in aqueous surface treatment liquid A surface-treated zinc-based plating, wherein the aqueous surface-treating liquid according to claim 1 or 2 is applied to the surface of a zinc-based plated steel sheet so that the Zr adhesion amount is 10 to 200 mg / m ² and dried. Manufacturing method of steel sheet. On the surface of the galvanized steel sheet, zirconium compound (a), fine particle silica (b), silane coupling agent-derived component (c), vanadic acid compound (d), phosphoric acid compound (e), nickel A compound (f) and an acrylic resin (g) are contained so as to satisfy the following conditions (1) to (6), and a surface treatment film having a Zr adhesion amount of 10 to 200 mg / m ² is provided. A surface-treated galvanized steel sheet.
(1) Mass ratio (b) / (a) = 0.1 to 1.2 of fine particle silica (b) and Zr equivalent amount of zirconium compound (a)
(2) Mass ratio (Si) / (a) = 0 of the total amount (Si) of Si in the fine particle silica (b) and the silane coupling agent-derived component (c) and the amount of Zr in the zirconium compound (a) .15-1.0
(3) Mass ratio (d) / (a) = 0.02 to 0.15 of V converted amount of vanadic acid compound (d) and Zr converted amount of zirconium compound (a)
(4) Mass ratio (e) / (a) = 0.03 to 0.30 of P equivalent of phosphoric acid compound (e) and Zr equivalent of zirconium compound (a)
(5) The mass ratio (f) / (a) between the Ni conversion amount of the nickel compound (f) and the Zr conversion amount of the zirconium compound (a) is 0.005 to 0.10.
(6) Mass ratio (g) / (x) = 0.18 to 0.75 between the acrylic resin (g) and the total amount (x) of the solid content of the film The surface-treated galvanized steel sheet according to claim 4, wherein the surface-treated film further contains a wax (h) so as to satisfy the following condition (7).
(7) Mass ratio (h) / (x) = 0.01-0.10 of wax (h) and total amount (x) of film solids