TWI544112B - Surface treatment galvanized steel plate with excellent corrosion resistance on damaged part and end face and manufacturing method thereof - Google Patents

Description

Surface-treated zinc-based plated steel sheet excellent in corrosion resistance of damaged portion and end surface, and method for producing same

The present invention relates to a chromium-free surface-treated steel sheet excellent in corrosion resistance, solvent resistance, and paintability in a zinc-based plated steel sheet having a small zinc basis weight ratio. The surface-treated steel sheet of the present invention is excellent in corrosion resistance of any of the flat portion, the alkali degreasing, and the processed portion, and is also resistant to chemicals, heat yellowing, molding processability, fingerprint resistance, electrical conductivity, and coating adhesion. Excellent sex. The present invention is particularly useful for zinc-based plated steel sheets. In general, the zinc basis weight of one side of the zinc-based plated steel sheet is about 20 g/m ² . When the weight per unit area of zinc is reduced, the corrosion prevention period of zinc becomes short, and corrosion occurs when used for a long period of time. More particularly, the present invention relates to a chromium-free surface-treated steel sheet which is excellent in corrosion resistance of an exposed iron portion such as a damaged portion, an end surface portion, and the like, and exhibits corrosion resistance and end surface corrosion resistance equal to or higher than the previous one even if the weight per unit area of zinc is small. Sex, and can inhibit red rust even after a long period of time.

In the past, zinc-plated steel sheets have been used in many fields in the fields of home appliances and building materials. Since the zinc-based plated steel sheet is insufficient in corrosion resistance and paintability (coating for pattern design) in a direct state, a product subjected to a chemical treatment such as chromate or zinc phosphate is produced. Among these products, the chromate-treated product may be used in a non-painting manner depending on the use. At this time, since the fingerprint adheres to the surface of the steel sheet to impair the appearance, a product of the fingerprint-resistant steel sheet which is further coated with a resin as a main component has been put into practical use. In addition, in recent years, with the European RoHS regulation, various types of chromium-free and fingerprint-resistant steel sheets which do not use hexavalent chromium and have a resin as a main component have been put into practical use.

In particular, in the field of home appliances, the fingerprint-resistant steel sheet has high quality in recent years, and it is necessary to have corrosion resistance, heat yellowing resistance, molding processability, and fingerprint resistance in a flat portion, an alkali degreasing, and a processed portion in advance. Various properties required for conductivity and coating properties.

As the previous surface treatment, most of the chromate treatment or phosphate treatment is carried out, followed by molding processing such as bending, extrusion, sliding, and the like, and then the molded article is coated. Further, depending on the application, there is a case where it is used without being coated.

When molding a fingerprint-resistant steel sheet, in order to reduce abrasion with the mold, a non-volatile or volatile press oil is used. When the state of the oil, the dirt, or the like adheres, the coating failure is caused, so the cleaning for removing it is performed. Most of the washing system uses a detergent containing a base or an acid as a main component. In order to shorten the processing time to improve the production efficiency, the detergent is often used at a higher concentration or a higher temperature than the previous one. Further, in the subsequent coating step, the spray coating is applied to the mainstream of the coating, because the fingerprint is peeled off during the cleaning, or the film is partially damaged, and the surface of the film is uneven, so the coating is performed. Poor appearance when applied. Further, at the time of coating, the solvent is volatilized and baked at a high temperature, and in the case of one side coating, since the non-coating surface is exposed to a high temperature environment, the film containing the resin component or the coloring component generates hot yellow. change. Or, when volatile stamping oil is used even when it is not coated, there is a step of volatilizing the stamping oil at a high temperature after the molding process. At this time, in the same manner as described above, the film containing the resin component or the coloring component is thermally yellowed. From a design point of view, this thermal yellowing can damage the value of the product.

Moreover, in home electric appliances, electrical conductivity and electromagnetic wave shielding of information equipment such as OA and AV are also necessary. In particular, in recent years, in terms of communication, the frequency is gradually increased, and it is important to have conductivity suitable for antistatic in advance. In order to exhibit excellent corrosion resistance and chemical resistance, it is inevitable that the coating is thick and resistant to fingerprints. Therefore, it is a technical issue to coexist with conductivity.

In recent years, the economic growth of emerging countries such as China and India has been remarkable, and the consumption of resources has rapidly accelerated. Zinc, one of the base metals, is also a target substance, and there is a concern that zinc is depleted in the long run. Because of the price increase in recent years, the fear of supply uneasiness has led to the attempt to resource the province.

For example, the prior zinc-plated steel sheet was plated with zinc of 20 g/m ² or more on one side. When the zinc basis weight of the zinc-plated steel sheet is reduced, it means that particularly at the position where the iron is exposed, it is difficult to suppress the corrosion of iron for a long period of time and the previous quality cannot be maintained.

A zinc-plated steel sheet having a basis weight of less than 20 g/m ² on one side, generally, when exposed to a corrosive environment for a long period of time, the rust-preventing ability is deteriorated according to the degree of the weight per unit area of zinc. . Previously, chromate or phosphate treatment to impart rust resistance was performed. As described above, the chromate treatment is not suitable for use due to environmental concerns such as RoHS control in recent years. In the case of phosphate treatment, it is difficult to form a film, and it is usually adhered to a film amount of ² g/m ² or more. Although it is possible to replenish insufficient corrosion resistance by thick film formation, on the other hand, conductivity is extremely poor, and it is impossible to impart conductivity which has been emphasized in recent years.

In the fingerprint-resistant steel sheet, not only the hexavalent chromium can be contained because of environmental control, but also various methods of use as described above, and it is not practical to satisfy all of the above. Previous proposals have revealed several techniques for chrome-free surface treated steel sheets.

For example, Patent Document 1 discloses a two-layer zinc-based plated steel sheet which is a surface of a zinc-based plated steel sheet and contains any one of a water-soluble resin having a specific structure, a decane coupling agent, a titanium compound, and a zirconium compound. The dried film obtained by the treatment liquid is set as the lower layer; and further, a urethane resin having a specific structure, a water-soluble epoxy resin, and a colloidal cerium oxide having a glass transition temperature of -40 ° C to 0 ° C is further included. A dried film obtained by a polyethylene wax having a specific particle diameter, a water-soluble organic solvent, and a water treatment liquid is provided as an upper layer. Although this technique has excellent corrosion resistance to a zinc-coated steel sheet having a zinc basis weight of 20 g/m ² or more, when it is used for a zinc-based plated steel sheet of less than 20 g/m ² , the corrosion resistance is extremely low and cannot be satisfied. Performance balance. In particular, in the position where the iron such as the damaged portion and the end surface portion is exposed, corrosion is remarkably generated, and sufficient corrosion resistance cannot be obtained.

Patent Document 2 discloses a zinc-based plated steel sheet containing a cationic polyurethane resin, a cationic phenol resin, a decane coupling agent, a manganese compound, a zirconium compound, a vanadium compound, and a specific physical property in a specific ratio. The treatment liquid of Fischer-Tropsch wax forms a surface-treated film. However, this technique is not necessarily satisfactory in terms of the durability of the processed portion, the corrosion resistance after alkali treatment, the chemical resistance, and the heat yellowing resistance. Since it is a one-layer process, in order to make the said performance satisfy and thicken it, it is low in electroconductivity, and it cannot satisfy all the items required for a fingerprint-resistant steel plate.

Further, since it is a one-layer treatment, when a zinc-based plated steel sheet having a zinc basis weight of less than 20 g/m ² is used, the damage of the damaged portion and the end surface is remarkably impaired.

Patent Document 3 discloses a surface-treated metal plate which is coated with a film composed of an alkali metal citrate, an organic resin, a solid water-dispersible wax, and a decane coupling agent. However, at this time, in the zinc-plated steel sheet having a zinc basis weight of less than 20 g/m ² , sufficient corrosion resistance cannot be obtained at a position where iron such as the damaged portion and the end surface portion is exposed.

Patent Document 4 discloses a surface-treated steel sheet which is a zirconium film formed of a chemical treatment liquid composed of hexafluorozirconic acid or an inorganic acid, and a water-dispersible polyurethane resin in the upper layer and water-soluble. A film composed of a polycarbodiimide resin, an organic titanium compound, a colloidal cerium oxide, and a polyethylene wax is coated. Although this technology can get better Corrosion resistance, but the coating adhesion is poor and can not meet the performance balance.

Patent Document 5 discloses a surface-treated metal sheet which is coated with an organic-inorganic composite film containing an aqueous resin, a phthalate compound, a polyolefin wax, and a colloidal cerium oxide. However, this technique has a zinc-coated steel sheet having a zinc basis weight of less than 20 g/m ² , and is not able to obtain sufficient corrosion resistance at the position where the iron such as the damaged portion and the end surface portion is exposed, but also after planar, alkali degreasing and processing. The Ministry also cannot obtain satisfactory corrosion resistance.

Patent Document 6 discloses a surface-treated steel sheet containing one selected from the group consisting of phosphoric acid, phosphate, cerium oxide, decane coupling agent, Ca, Mn, Mg, Ni, Co, Fe, and Ca-based compounds in the lower layer or Two or more kinds of films are formed by coating a film containing an organic resin on the upper layer. At this time, the zinc-plated steel sheet having a zinc basis weight of less than 20 g/m ² is not only flat, alkali degreased, and processed portion, but also cannot satisfy the damage of the damaged portion and the end surface.

Patent Document 7 discloses an aqueous resin composition composed of an alkali silicate and a water-soluble resin. Even with this technique, in a zinc-based plated steel sheet having a zinc basis weight of less than 20 g/m ² , not only the corrosion resistance at the position where the iron such as the damaged portion and the end surface portion is exposed is not obtained, but also after the flat surface and the alkali degreasing. And the processing department is also unable to obtain satisfactory corrosion resistance.

Patent Document 8 discloses a zinc-plated steel sheet which is formed of a film selected from an oxide or a hydroxide of Si, Zr, Ti, Hf in the first layer, and is composed of a carboxyl group and a hydroxyl group in the upper layer thereof. It is formed by a film composed of an organic resin and a crosslinking agent. This technique is a zinc-plated steel sheet having a zinc basis weight of less than 20 g/m ² , and it is not possible to obtain sufficient corrosion resistance at the position where the iron such as the damaged portion and the end surface portion is exposed, and it is not possible to satisfy the demand quality in recent years. Say it can be satisfied.

Patent Document 9 discloses a zinc-plated steel sheet which is coated on the outermost layer with an organic resin having an anionic functional group, a cationic metal element selected from the group consisting of Li, Na, K, Mg, Ca, and Sr, and a crosslinking agent; Further, the base film is coated with a decane coupling agent or an organic resin. In this case, when a zinc-plated steel sheet having a zinc basis weight of less than 20 g/m ² is used, not only the corrosion resistance at the position where the iron such as the damaged portion and the end surface portion is exposed is not obtained, but also the flat portion and the alkali degreasing cannot be satisfied. Basic corrosion resistance of the processing department and the like.

Patent Document 10 discloses a zinc-plated steel sheet which is a crosslinking agent such as an organic resin, an isocyanate compound or a carbodiimide compound, an organic rust inhibitor, cerium oxide, phosphoric acid, cerium and zirconium compounds, or cerium ( Guanidine) The coating formed by the compound and wax. In this case, when a zinc-plated steel sheet having a zinc basis weight of less than 20 g/m ² is used, not only the corrosion resistance at the position where the iron such as the damaged portion and the end surface portion is exposed is not obtained, but also the flat portion and the alkali degreasing cannot be satisfied. Basic corrosion resistance of the processing department and the like. Further, red rust is likely to occur at the position where the iron is exposed, and the corrosion resistance over a long period of time is insufficient.

Patent Document 11 discloses a zinc-plated steel sheet which is coated with a film composed of an organic resin composed of an epoxy resin or an anthracene derivative, a decane coupling agent, phosphoric acid or hexafluorometal acid in a first layer; The layer is coated with a film containing an epoxy resin, a urethane resin, and an organometallic compound, and the organometallic compound is one or more selected from the group consisting of an organic titanium compound, an organic zirconium compound, and an organoaluminum compound. In this case, when a zinc-based plated steel sheet having a zinc basis weight of less than 20 g/m ² is used, the corrosion resistance of the damaged portion and the end surface portion is insufficient, and an appearance color change such as yellowing occurs on the surface of the steel material after heating.

Patent Document 12 discloses a zinc-plated steel sheet which is coated with a polyurethane resin, cerium oxide, a polyolefin resin, phosphoric acid, and a compound selected from the group consisting of carbon-containing diimine-based compounds. A film made of one or more compounds of an oxazoline group compound and a titanium compound. In this case, when a zinc-plated steel sheet having a zinc basis weight of less than 20 g/m ² was used, the corrosion resistance of the damaged portion and the end portion could not be retained, and the performance of satisfying the flat portion, the alkali degreasing, and the corrosion resistance of the processed portion could not be obtained. Further, red rust is likely to occur at the position where the iron is exposed, and the corrosion resistance over a long period of time cannot be satisfied.

Prior technical literature Patent literature

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2004-2958

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2008-194839

[Patent Document 3] Japanese Patent No. 2998790

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2011-17082

[Patent Document 5] Japanese Patent Laid-Open Publication No. 2002-212754

[Patent Document 6] Japanese Patent Laid-Open Publication No. 2003-213396

[Patent Document 7] Japanese Patent Laid-Open No. Hei 7-316443

[Patent Document 8] Japanese Patent Laid-Open Publication No. 2010-47796

[Patent Document 9] Japanese Patent Laid-Open Publication No. 2009-248460

[Patent Document 10] Japanese Patent Laid-Open Publication No. 2005-281863

[Patent Document 11] Japanese Patent Laid-Open Publication No. 2008-910

[Patent Document 12] Japanese Patent Laid-Open Publication No. 2008-25023

Compared with the conventional surface-treated zinc-based plated steel sheet obtained by coating an organic resin on a chromate film, the conventional chromium-free surface-treated zinc-based plated steel sheet is processed in a single layer. Although it is economical, the performance balance of the required characteristics such as corrosion resistance, heat yellowing resistance, molding processability, fingerprint resistance, electrical conductivity, and paintability after the flat portion, the alkali degreasing, and the processed portion is still insufficient.

Further, in the technique of forming two layers, since the lower layer contains a resin component, heat yellowing resistance and conductivity are inferior, and similarly, the performance balance with respect to required characteristics is insufficient. Even if the resin is not used in the lower layer, the performance balance is not sufficient. Further, any of these techniques is a case where a surface-treated zinc-based plated steel sheet having a zinc basis weight of 20 g/m ² or more is used. When a zinc-based plated steel sheet having a one-side zinc basis weight of 1 to 15 g/m ² is used, the above-described technique is incapable of obtaining satisfactory corrosion resistance. In particular, the damaged portion and the end surface portion are significantly deteriorated. Reducing the zinc basis weight of the zinc-based plated steel helps to suppress the depletion of zinc resources and the increase in price. As a result, the zinc-based plated steel sheet can be stably supplied for a long period of time.

An object of the present invention is to provide a surface-treated zinc-based plated steel sheet which is obtained by using a zinc-based plated steel sheet, corrosion resistance, chemical resistance, heat yellowing resistance, and molding of any of a flat portion, an alkali degreasing, and a processed portion. It is excellent in balance of various properties such as processability, fingerprint resistance, electrical conductivity, and coating adhesion, and provides a surface-treated steel sheet, particularly a zinc plating system of 1 to 15 g/m ^{2 which} is reduced in weight per unit area of zinc. In the case of a steel sheet, the corrosion resistance of the damaged portion and the end surface is inevitably lowered, and the corrosion resistance is also excellent as compared with the zinc-based plated steel having a zinc basis weight of 20 g/m ² or more.

The inventors of the present invention have focused on the means for solving the problems of the prior art, and have found that a surface has been repeatedly studied in order to ensure that various characteristics required for the surface treatment of the zinc-based plated steel are not used at all. The zinc-based plated steel sheet is excellent in balance of properties, and has good corrosion resistance, solvent resistance, moldability, electrical conductivity, and coating property in any of the flat portion, the alkali degreasing, and the processed portion, and the damaged portion and the end surface. The present invention has been completed in that corrosion resistance is excellent and red rust does not easily occur over a long period of time. Specifically, it is a surface-treated zinc-based plated steel sheet having a zinc plating layer on both sides of the steel sheet, and further having an acidic inorganic coating layer and an alkaline organic-inorganic composite coating layer on the surface of the zinc plating layer. The two-layer film formed, the acid inorganic coating layer has a film weight of 0.01 to 0.5 g/m ² ; and the basic organic-inorganic composite coating layer has a film weight of 0.5 to 3 g/m ² , wherein the acidic inorganic coating layer An acidic inorganic coating agent (L) of pH 2 to 5 obtained by adding at least a zirconium compound (A), a water-dispersible cerium oxide (B), a magnesium compound (C), a vanadium compound (D), and a fluorine compound (E) a layer formed by coating; and the basic organic-inorganic composite coating layer is added with at least an anionic urethane resin (U) having a weight average molecular weight of 100,000 to 200,000, an alkali citrate (V), A layer formed by coating a basic organic-inorganic composite coating material (M) having a pH of from 9 to 12, which is a titanium alkoxide (W), a polycarbodiimide resin (X), and a decane coupling agent (Y). Moreover, "zinc plating" and "zinc plating" in the scope of the present application and the present specification mean plating with zinc as a main component (50% by weight or more) and constituting a plating component ( The plated metal) is not only a single aspect of zinc but also a concept of a plurality of metals (so-called alloy plating) containing other metals (for example, Ni or the like).

That is, the present invention is

(1) A surface-treated zinc-based plated steel sheet having a zinc plating layer on both sides of a steel sheet, and further having an acidic inorganic coating layer and an alkaline organic-inorganic composite coating on the surface of the zinc plating layer a two-layer film composed of a layer, wherein the weight of the acidic inorganic coating layer is 0.01 to 0.5 g/m ² ; and the weight of the alkaline organic-inorganic composite coating layer is 0.5 to 3 g/m ² , wherein the acidic inorganic coating is The layer is an acidic inorganic coating agent having a pH of 2 to 5 obtained by adding at least a zirconium compound (A), a water-dispersible cerium oxide (B), a magnesium compound (C), a vanadium compound (D), and a fluorine compound (E) ( L) a layer formed by coating; and the alkaline organic-inorganic composite coating layer is added with at least an anionic urethane resin (U) and an alkali citrate (V) having a weight average molecular weight of 100,000 to 200,000. A layer formed by coating a basic organic-inorganic composite coating material (M) having a pH of from 9 to 12, which is a titanium alkoxide (W), a polycarbodiimide resin (X), and a decane coupling agent (Y).

(2) A surface-treated zinc-based plated steel sheet according to (1), wherein the zinc-based plated steel sheet has a zinc basis weight of from 1 to 15 g/m ² .

(3) A surface-treated zinc-based plated steel sheet according to (1) or (2), wherein the basic organic inorganic coating layer contains a water-dispersible wax (Z).

(4) The surface-treated zinc-based plated steel sheet according to any one of (1) to (3), wherein the anionic urethane resin (U) contained in the alkaline organic-inorganic composite coating layer It has a carboxyl group or a salt thereof.

(5) A surface-treated zinc-based plated steel sheet according to (3) or (4), wherein the metal (a) contained in the zirconium compound (A) and the anionic amine formic acid contained in the basic organic-inorganic composite coating layer The mass ratio of the solid content of the ester resin (U) is (a) / (U) = 0.001 to 0.4; the mass ratio of the solid component of the water-dispersible ceria (B) to the anionic urethane resin (U) (B) / (U) = 0.001 to 1; the mass ratio of the metal (c) to the solid content of the alkali silicate (V) contained in the magnesium compound (C) is (c) / (V) = 0.001 to 0.5 The mass ratio of the metal (d) to the solid content of the alkali silicate (V) contained in the vanadium compound (D) is (d) / (V) = 0.001 to 0.5; the fluorine element (e) of the fluorine compound (E) The mass ratio of the solid component of the metal (c) contained in the magnesium compound (C) is (e) / (c) = 0.1 to 30; the metal (w) and the alkali bismuth contained in the titanium alkoxide (W) The mass ratio of the solid content of the acid salt (V) is (w) / (V) = 0.01 to 1; the mass ratio of the solid content of the polycarbodiimide resin (X) to the anionic urethane resin (U) Is (X) / (U) = 0.001 to 0.5; the mass ratio of the solid component of the decane coupling agent (Y) to the anionic urethane resin (U) is (Y) / (U) = 0.001 to 0.5; Mass of the solid content of the wax dispersion (Z) and an anionic resin the urethane (U) ratio of (Z) / (U) = 0.01 to 0.2.

(6) The surface-treated zinc-based plated steel sheet according to any one of (1) to (5), wherein the alkaline organic-inorganic composite coating layer has a temperature greater than 100 ° C The glass transfer temperature.

(7) The surface-treated zinc-based plated steel sheet according to any one of (1) to (6), wherein the zinc-based plated steel sheet is a zinc-based plated steel sheet.

(8) A method for producing a surface-treated zinc-based plated steel sheet comprising a surface of a zinc-based plated steel sheet having a zinc plating layer on both sides of a steel sheet, and forming any one of (1) to (6) a two-layer film forming step of an acidic inorganic coating layer and an alkaline organic-inorganic composite coating layer, wherein the two-layer film forming step includes a step of forming an acidic inorganic coating layer, which is performed by the zinc-based plating After coating the acidic inorganic coating material (L) on the steel sheet, drying it at 50° C. or higher and 100° C. or lower; and forming a basic organic-inorganic composite coating layer, coating the upper layer of the acidic inorganic coating layer to coat the alkaline layer After the organic-inorganic composite coating agent (M), it is dried at an reaching temperature of 100 ° C or more and less than 200 ° C.

(9) A surface-treated zinc-based plated steel sheet obtained by the production method of (8).

The surface-treated zinc-based plated steel sheet of the present invention has a zinc basis weight of 1 to 15 g/m ² on one surface, and corrosion resistance and resistance to any of the flat portion, the alkali degreasing, and the processed portion without using chromium. Each property of chemical properties, heat yellow resistance, moldability, fingerprint resistance, electrical conductivity, and paintability shows an excellent balance of properties. Further, the surface-treated zinc-based plated steel sheet having a zinc basis weight of 20 g/m ² or more on one of the previous surfaces has an excellent damage portion and end surface corrosion resistance of equal or higher. The surface-treated zinc-based plated steel sheet of the present invention can be used without coating or can be used by coating. Therefore, since the risk balance of zinc resources is alleviated by overcoming environmental problems and the performance balance of the aforementioned characteristics is satisfied, it has a very important use value in the industry.

Hereinafter, an aspect of the present invention will be described in detail. However, the technical scope of the present invention is not limited by this form.

Surface Treatment Zinc Plated Steel Plate

The surface-treated zinc-based plated steel sheet of the present embodiment has a zinc plating layer on both surfaces of the steel sheet, and further has an acidic inorganic coating layer and a basic organic-inorganic composite coating layer on the surface of the zinc plating layer. A surface-treated zinc-based plated steel sheet having a film weight of the acidic inorganic coating layer of 0.01 to 0.5 g/m ² and a coating weight of the basic organic-inorganic composite coating layer of 0.5 to 3 g/m ² . Here, the acidic inorganic coating layer is a pH 2 to 5 in which a zirconium compound (A), a water-dispersible cerium oxide (B), a magnesium compound (C), a vanadium compound (D), and a fluorine compound (E) are added. a layer formed by coating an acidic inorganic coating agent (L); and the basic organic-inorganic composite coating layer is an anionic urethane resin (U) or an alkali citrate having a weight average molecular weight of 100,000 to 200,000. a layer formed by coating a basic organic-inorganic composite coating agent (M) of pH 9 to 12 composed of (V), a titanium alkoxide (W), a polycarbodiimide resin (X), and a decane coupling agent (Y) . Here, the two-layer film of the present embodiment has an acidic inorganic coating layer as a lower layer (a layer formed on the zinc plating layer); and a basic organic-inorganic composite coating layer as an upper layer (formed on the acidic inorganic coating layer) Floor). Hereinafter, a method of producing a surface-treated zinc-based plated steel sheet of the present embodiment (hereinafter also referred to simply as "surface-treated steel sheet") will be described.

"Manufacturing method of surface-treated zinc-based plated steel sheet"

Next, a method of producing the surface-treated steel sheet of the present embodiment will be described. The surface-treated steel sheet according to the present aspect includes a step of applying an acidic inorganic coating material (L) to a substrate, that is, a zinc-based plated steel sheet, and then drying the mixture to form an acidic inorganic coating layer; and coating the basic organic-inorganic composite coating agent After (M), it is dried to form a basic organic-inorganic composite coating layer. Hereinafter, the respective components, tasks, addition amounts, and the like of each of the agents used in the production method will be described.

<Acid inorganic coating agent (L)>

The acidic inorganic coating agent (L) is obtained by adding at least a zirconium compound (A), a water-dispersible cerium oxide (B), a magnesium compound (C), a vanadium compound (D), and a fluorine compound (E). Hereinafter, each raw material component will be described in detail.

(ingredient A: zirconium compound)

In the acidic inorganic coating material (L) of the present embodiment, it is presumed that a part of the zirconium compound (A) is reacted with the fluorine compound (E) in the coating agent (L) to partially ionize the fluorine.

_{^{2 H + + ZrF 6 2- →}} 2 H + + ZrF 4 +2 F - like

The fluoride ion (F ^- ) system has a good etching ability. Especially in acidic conditions, it has good etching ability. Therefore, when the acidic inorganic coating material of the present embodiment is brought into contact with a surface of a metal material (in this embodiment, a zinc-based plated steel sheet which is a substrate of a surface-treated zinc-based plated steel sheet) to form a treated film, the present embodiment is considered to be The fluoride ion in the acidic inorganic coating material dissolves the surface thereof as appropriate, and forms a substance such as a reaction layer at the boundary between the treated film and the surface of the metal material. Therefore, the coating film on the surface of the zinc-based plated steel sheet is remarkably improved in adhesion, and the flatness, the alkali degreasing, and the corrosion resistance of the processed portion are also improved by the adhesion.

The effect of adding the component A will be explained in more detail. By the action of the zirconium compound (A) and the fluorine compound (E) added to the acidic inorganic coating material, a film in which zirconium and fluorine coexist is formed, and the end surface portion in which the iron portion is exposed exhibits an extremely excellent effect. A battery of iron and zinc is usually formed in a portion where the iron portion is exposed to promote anodic dissolution of zinc. On the other hand, in the cathode portion, alkali concentration occurs due to reduction of dissolved oxygen, and excessive zinc consumption and corrosion are performed. When exposed to a corrosive environment for a long period of time, zinc consumption and corrosion are insufficient, and the iron surface is corroded. In the surface-treated zinc-coated steel sheet of the present embodiment, in the film in which zirconium and fluorine coexist, the fluoride is discharged to serve as a buffer for raising the pH at the cathode portion. That is, as a result, excessive consumption of corrosion at the anode portion is suppressed and the corrosion prevention is appropriately maintained. Therefore, the coexistence film derived from the zirconium compound (A) and the fluorine compound (E) exhibits excellent corrosion resistance on the end surface portion. In the surface-treated zinc-based plated steel sheet according to the present aspect, excessive consumption corrosion is suppressed by the presence of fluoride ions on the surface of the zinc-based plated steel sheet having a zinc basis weight of 1 to 15 g/m ² on one surface, compared with the use. The surface-treated zinc-based plated steel sheet having a zinc basis weight of 20 g/m ² or more after the treatment with the surface treatment agent has the same end face corrosion resistance and can suppress the occurrence of red rust.

Examples of the zirconium compound (A) of the present embodiment include zirconium hydrofluoride acid, zirconium ammonium fluoride, basic zirconium carbonate, zirconium nitrate, zirconium acetate, and hydrogen and oxygen. Zirconium, zirconium oxide, etc. These types may be used in combination of one type or two or more types.

Here, when determining the addition amount of the component (A) in the acidic inorganic coating material, it is preferable to consider the addition amount of the component (U) in the basic organic-inorganic composite coating material. Specifically, the mass ratio of the metal (a) contained in the component (A), that is, the zirconium element (a) to the solid content of the component (U) is preferably (a) / (U) = 0.001 to 0.4. . It is preferably (a) / (U) = 0.005 to 0.3, more preferably (a) / (U) = 0.01 to 0.1. When (a)/(U) is less than 0.001, the corrosion resistance including the corrosion resistance of the damaged portion and the corrosion resistance of the end portion is deteriorated as a whole, and when it is more than 0.4, the corrosion resistance of the damaged portion is deteriorated, and the coating adhesion is also low. . This is because the acidic inorganic coating layer is also formulated in the same solid component mass ratio.

(Component B: water-dispersible cerium oxide)

In the case of the water-dispersible cerium oxide (B) of the present embodiment, the part (1) may be partially dissolved in the acidic inorganic coating material, but the total amount thereof is not completely dissolved, and the acidic inorganic coating of the present embodiment is used. The treatment film formed on the surface of the metal material is left as a solid material, and (2) is not particularly limited as long as it has an oxide as a main component (may be a powder or a liquid). Here, as the water-dispersible cerium oxide (B), the average particle diameter in air is preferably from 0.001 to 100 μm, and more preferably from 0.001 to 1 μm. Too large particles will protrude from the film (acidic inorganic coating layer), become a film defect and easily become a corrosion starting point. Therefore, an appropriate particle size is necessary, and when the particle diameter is small, there is an advantage that adhesion or the like is easily obtained. The surface coating agent of the present embodiment preferably contains water-dispersible cerium oxide (B) in a colloidal state.

More specifically, the water-dispersible cerium oxide is liquid phase cerium oxide synthesized from a liquid phase; and gas phase cerium oxide synthesized from a gas phase.

Examples of the liquid phase cerium oxide include SNOWTEX C, SNOWTEX O, SNOWTEX N, SNOWTEX S, SNOWTEX UP, SNOWTEX PS-M, SNOWTEX ST-OL, SNOWTEX 20, SNOWTEX 30, and SNOWTEX 40 (either one is Nissan Chemical Industry Co., Ltd.).

Further, examples of the gas phase cerium oxide include AEROSIL 50, AEROSIL 130, AEROSIL 200, AEROSIL 300, AEROSIL 380, AEROSIL TT600, AEROSIL MOX80, and AEROSIL MOX170 (all of which are manufactured by AEROSIL, Japan).

Only one of the liquid phase cerium oxide and the gas phase cerium oxide may be used as the water-dispersible cerium oxide, and a plurality of them may be used in combination.

The water-dispersible cerium oxide (B), which functions as a binder in the formation of a film, has the task of forming a continuous film. In particular, in the preparation of zirconium hydrofluoric acid (A1) and water-dispersible cerium oxide (B), it is effective to uniformly arrange fluoride ions in the film, and at the same time, it has an excess of fluoride ions. The task of adjusting agents. When the fluoride ions are excessively present, it is disadvantageous in terms of corrosion resistance and coating adhesion of the damaged portion. The mass ratio (e)/(B) of the solid content of the fluoride ion system to the water-dispersible ceria (B) is preferably from 0.05 to 0.5. It is preferably from 0.1 to 0.4. More preferably, it is from 0.15 to 0.35. Excellent corrosion resistance of the end face and corrosion resistance of the damaged part in such a range The sexual system is good, and it can also have coating adhesion.

When the amount of the component (B) to be added to the acidic inorganic coating material is determined, it is preferable that the amount of the component (U) in the basic organic-inorganic composite coating material is also considered in the same manner as the component (A). . Specifically, the mass ratio of the solid content of the water-dispersible ceria (B) to the component (U) is preferably (B) / (U) = 0.001 to 1. Preferably, (B) / (U) = 0.005 to 0.5, more preferably (B) / (U) = 0.01 to 0.3. When (B)/(U) is less than 0.001, the corrosion resistance including the corrosion resistance of the damaged portion and the corrosion resistance of the end portion is deteriorated as a whole, and when it is more than 1, the corrosion resistance of the damaged portion is deteriorated, and the coating adhesion is also low. .

(ingredient C: magnesium compound)

Further, the acidic inorganic coating agent of the present embodiment contains the magnesium compound (C) as a raw material. The acidic inorganic coating agent obtained by adding the components (A), (B), and (E) is a solution, and the viscosity of the solution rises and gels soon. This is because of the product produced by the reaction of zirconium fluoride with cerium oxide. The acidic inorganic coating agent obtained by adding the above components (A), (B), and (E) is difficult to coexist in an aqueous solution, particularly an acidic aqueous solution having a pH of about 2.0 to 5.0, and the time passes. At the same time, the viscosity of the aqueous solution increases and there is a tendency to gel.

On the other hand, in the acidic inorganic coating agent which added the components (A) to (E), such a phenomenon does not easily occur. Even after a certain period of time (for example, a period of several weeks to several months) after the manufacture, the viscosity can be maintained at a low state (that is, the stability of the coating agent is good) and it can withstand industrial use. The inventors of the present invention presume that this property is the influence of the presence of the magnesium compound (C). This point is disclosed below.

In that acidic inorganic coating agent of the present aspect, since the magnesium compound (C) based easily and F ^- Reaction (trapping), the acidic inorganic covering agent present in the form of in the presence of free F ^- based substantially absent .

On the other hand, when the magnesium compound (C) is not added, it is considered that the fluorine ion (F-) dissolves the solid surface of the water-dispersible ceria (B), so that the water-dispersible ceria (B) The fusion occurs, and a three-dimensional network is slowly formed and the viscosity is increased and gelation occurs.

Since the acidic inorganic coating agent of this embodiment contains the above-mentioned magnesium compound (C), it is considered that the free F ^- system is not present. Therefore, it is considered that the zirconium compound (A) and the water-dispersible cerium oxide (B) can coexist in a stable manner.

Further, it is considered that the above-mentioned magnesium compound (C) is not only capable of trapping F ^- but also acts as an inhibitor for suppressing corrosion, and contributes to improvement of corrosion resistance.

Since these lines that trap F ^- the capacity is relatively high, so that the stability of the coating agent of the present aspect further improved. This is described in more detail. Although the effect derived from the magnesium compound (C) present in the coating layer is not clearly understood, it contributes to the stabilization of the corrosion product generated in a corrosive environment. It is considered that corrosion of the metal is caused by exposure to a corrosive environment, accompanied by a decrease in pH caused by zinc dissolution and reduction reaction of dissolved oxygen, resulting in destruction of corrosion products protecting the zinc surface. However, the magnesium compound (C) can contribute to corrosion resistance even when it is exposed to a high pH environment but produces a stable corrosion product.

The acidic inorganic coating agent of the present form is as follows The form (compound) contains the magnesium element (c), and in the case of such a form (compound), it is preferable in terms of improving the corrosion resistance.

Examples of the magnesium compound (C) include magnesium nitrate, magnesium sulfate, magnesium carbonate, magnesium hydroxide, magnesium fluoride, magnesium ammonium phosphate, magnesium hydrogen phosphate, and magnesium oxide.

These types may be used in combination of one type or two or more types. Further, in the acidic inorganic coating material of the present embodiment, the magnesium element (c) may be contained as a magnesium metal monomer.

Among such forms (compounds) of the magnesium compound (C), oxides and hydroxides are particularly preferred. The reason for this is to have a coating metal material having a treatment film formed using the coating agent of the present embodiment as a base, and the corrosion resistance is further improved. Among these, only one component may be added or a plurality of species may be added.

It is considered that the components derived from the magnesium compound (C) are dissolved in the coating agent of the present form and exist in a molecular or ion state.

In the acidic inorganic coating material of the present aspect, the magnesium element (c) in the magnesium compound (C) contains a molar amount (γ) (mol/L) and a fluorine element containing a molar amount (α) (mol/L) The ratio (γ/α) is preferably 0.001 to 1.7, more preferably 0.005 to 1.4, and most preferably 0.01 to 1.0. In such a range, since the stability of the acidic inorganic coating material of the present embodiment is good, and the corrosion resistance of the coating film formed on the surface of the metal material is further improved by using the acidic inorganic coating material of the present embodiment, good.

Here, when determining the addition amount of the component (C) in the acidic inorganic coating material, the components in the basic organic-inorganic composite coating material are also considered. The amount of addition of (V) is preferably. Specifically, in the acidic inorganic coating material of the present embodiment, the metal component of the magnesium compound (C), that is, the solid content ratio (c)/(V) of the magnesium element (c) and the component (V) is 0.001. It is better to 0.5. It is preferably (c) / (V) = 0.005 to 0.3, more preferably (c) / (V) = 0.01 to 0.1.

When (c)/(V) is less than 0.001, not only the sufficient chemical stability but also the corrosion resistance is not obtained. On the other hand, when (c) / (V) is more than 0.5, the stability of the drug is also poor. This is because the acidic inorganic coating layer is also formulated in the same solid component mass ratio.

(ingredient D: vanadium compound)

Further, the acidic inorganic coating agent of the present embodiment is preferably a vanadium compound (D) as a raw material. The vanadium compound (D) is effective as a corrosion inhibitor and is effective for improving the corrosion resistance level. Further, when the vanadium compound (D) is used, the stability of the acidic inorganic coating material of the present embodiment is preferably good. This effect is particularly advantageous in that the acidic inorganic coating agent is large and contributes to an improvement in stability.

This is because the estimated acidic inorganic coating agent of this embodiment, the vanadium compound (D) will be located with the fluorine compound (E) or a portion of the F ^- the emission of a zirconium compound (A).

Further, it is considered that the vanadium compound (D) further contributes to the improvement of corrosion resistance as a function of an inhibitor of corrosion. Further details this. With the dissolution of zinc in a corrosive environment and the elution of the vanadium compound (D), the vanadium compound (D) is changed to a state in which it is less likely to be eluted in water and is present on the surface of the zinc plating, thereby exhibiting corrosion resistance. .

The vanadium compound (D) has a compounding ability to form a complex The compound of force is especially good. The vanadium compound (D) is not particularly limited as long as it is a compounded vanadium compound, and examples thereof include a compound of propionic acid, oxalic acid, gluconic acid, tartaric acid, malic acid, ascorbic acid, acetamidine acetone, and sulfuric acid. One or two or more.

In the acidic inorganic coating material of the present aspect, the vanadium compound (D) is a solid content ratio of the metal contained in the vanadium compound (D), that is, the vanadium element (d), in the acidic inorganic coating material of the present embodiment. It is preferably (d) / (V) = 0.001 to 0.5, more preferably 0.005 to 0.3, and particularly preferably 0.01 to 0.1. In such a range, it is preferable to achieve the effect of further improving the storage stability and the runnability (operability) of the acidic inorganic coating material of the present embodiment.

(ingredient E: fluorine compound)

Examples of the fluorine compound (E) include hydrofluoric acid, ammonium fluoride, sodium fluoride, zirconium hydrofluoride, titanium hydrofluoride, barium hydrofluoride, ammonium fluorozirconate, ammonium fluorotitanate, and fluoroquinone. Potassium acid, ammonium fluoroantimonate, and the like.

These types may be used in combination of one type or two or more types. When the zirconium compound (A) is a fluorine compound, the fluorine compound (E) may not be mixed.

The fluorine compound (E) has a task of suppressing excessive pH rise by buffering the alkali component generated in the corrosive environment as described above by dissociation of fluoride ions. Therefore, the zinc corrosion-preventing ability can be sufficiently exhibited, and at the same time, the generated corrosion product can be stabilized, and both zinc corrosion and iron corrosion can be exerted.

The solid content ratio (e)/(c) of the fluorine element (e) of the fluorine compound (E) to the metal (c) of the magnesium compound (C) is preferably 0.1 to 30, and is for (e)/( c) The lower limit value is preferably 0.3, more preferably 1 and most preferably 2, and most preferably 3. On the other hand, for the upper limit of (e)/(c), 20 is preferable, 10 is more preferable, 8 is particularly preferable, and 6 is most preferable. When the amount of the fluorine compound (E) is not more than 0.1 in terms of the mass ratio of the solid component, when the (e)/(c) is less than 0.1, sufficient pH buffering ability cannot be exhibited, and the corrosion resistance of the damaged portion and the end surface portion is deteriorated. When (e)/(c) is more than 30, since the amount of the dissociated fluoride ions is excessively increased, the corrosion resistance of the damaged portion is deteriorated.

(ingredient: other optional ingredients)

The optional component of the acidic inorganic coating agent of the present embodiment may be a filler, a surfactant, an antifoaming agent, a leveling agent, an antibacterial agent, a coloring agent, or the like, and may be added in a range that does not impair the performance of the film.

(ingredient: liquid medium)

The acidic inorganic coating agent of this form is an aqueous system. The term "water system" means that the solvent contains 60% or more of water as a main component. The solvent may be water-only, and a water-soluble organic solvent such as one or more kinds of one or more kinds of polyols, ketones, and ethylene glycols may be used in combination for the purpose of adjusting the drying property of the coating film and the viscosity of the coating material.

(total concentration)

The total concentration in the acidic inorganic coating material of the present form {zirconium compound (A), water-dispersible cerium oxide (B), magnesium compound (C), vanadium compound (D), fluorine compound (E), and other components (Total concentration of all of the solvents other than the solvent contained in the acidic inorganic coating material of the present embodiment) is preferably from 1 to 50% by mass. The total concentration is more preferably 2 to 40% by mass, and most preferably 3 to 20% by mass. When such a range is It is preferred that the liquidity of the coating agent and its practical use are reasonable. Here, the total concentration referred to herein is the concentration calculated from the mass of the solid component. More specifically, the concentration is calculated from the mass of the solid component remaining after drying the acidic inorganic coating material of the present form at about 100 °C.

(liquid)

The acidic inorganic coating agent of the present embodiment is an aqueous solution obtained by adding the above-mentioned components, and the pH is preferably 2.0 to 5.0, more preferably 2.5 to 4.5. In such a range, it is preferable to achieve an effect of suppressing etching of the surface of the metal material and further improving the workability.

In the acidic inorganic coating material of the present embodiment, the components (A) to (E) are used as a raw material in an appropriate amount and are appropriately acidic, and the following effects are obtained. A surface-treated zinc-based plated steel sheet having fingerprint resistance can be used without being coated. Therefore, it is necessary and desirable to maintain the appearance of the steel itself after the surface treatment. The reason for the change in the appearance color of the steel material is surface roughness, refractive index change, and the like. In such a case, when the acidic inorganic coating material of the present embodiment is used, the surface of the steel material is appropriately etched due to appropriate acidity. Therefore, even if the component having a refractive index different from that of the steel material is coated, the unevenness of the surface of the steel material increases, and the diffused reflection of light increases and the effect of suppressing the change in appearance color is obtained.

When it is necessary to adjust the pH of the acidic inorganic coating material of this form, it is possible to add an appropriate acid (for example, acetic acid, nitric acid, phosphoric acid, a salt thereof, or the like) or a base (for example, ammonia, an organic amine or a salt thereof). .

<Alkaline organic-inorganic composite coating agent (M)>

The basic organic-inorganic composite coating agent of the present aspect is characterized in that at least an anionic urethane resin (U), an alkali citrate (V), a titanium alkoxide (W) having a weight average molecular weight of 100,000 to 200,000 is added. Polycarbodiimide resin (X), decane coupling agent (Y). The basic organic-inorganic composite coating layer can further contain a water-dispersible wax (Z). The solid content ratio of the component can be adjusted to be within the range described below, and the agent can be prepared into an alkaline organic-inorganic composite coating material, and the agent can be applied to an acidic inorganic coating layer or a zinc-based plating layer. The surface of the steel sheet is dried to form an alkaline organic-inorganic composite coating layer. When the basic organic-inorganic composite coating layer formed on the acidic inorganic coating layer is formed separately from the zinc-based plated steel sheet without forming an acidic inorganic coating layer, any of the flat surface, the alkali degreasing, and the processed portion Corrosion resistance, damage to the damaged portion and end face, chemical resistance, and moldability are improved. Further, it is possible to exhibit an optimum effect including heat yellowing resistance, fingerprint resistance, electrical conductivity, and paintability. In particular, it has a significant effect on the damaged part and the end face, and helps to suppress the occurrence of red rust. Hereinafter, the tasks and addition amounts of the respective components will be described in detail.

(Component U: anionic urethane resin)

The anionic urethane resin (U) used in the basic organic-inorganic composite coating material of the present embodiment forms the main component of the coating layer of the present embodiment, and has corrosion resistance, chemical resistance, moldability, and heat resistance. The basic characteristics of yellow denaturation and coating. Here, the anionic urethane resin (U) is water-dispersible.

Since the urethane resin has high adhesion to the base film layer (here, refers to interlayer adhesion) and can form a dense film, it has zinc to be formed. It is an effect of separating external factors such as water, oxygen, and inorganic salts containing acid and alkali, and has an effect of exhibiting corrosion resistance and chemical resistance. By setting the type of the polyol forming the skeleton of the urethane resin to a polyether type or a polyester type, it is possible to obtain a urethane resin having a balance between flexibility and elasticity, and it is also possible to improve the adhesion. Further, by imparting toughness by appropriately adding branches, a dense film can be formed. By the action of these recombination, effects such as mutual entanglement between polymer chains and interaction between urethane groups are effectively exhibited, and corrosion resistance, chemical resistance, coating properties, and the like are exhibited. The type of the polyol as the urethane resin can be roughly classified into a polyether, a polyester, and a polycarbonate. Since polyester and polycarbonate have a polar group, the intermolecular interaction is strong and is suitable as a strong film. On the other hand, since the polyether does not have a polar group, the intermolecular interaction is a mechanically inferior film when compared with polyester or polycarbonate. However, since it has a chemically stable ether group, it is effective for chemical resistance. On the other hand, polycarbonate-based polyols are advantageous in terms of chemical and mechanical stability, and have the disadvantage of being somewhat expensive. From the above, the water-dispersed urethane resin of the present embodiment is preferably a polyether-based or polyester-based system. Here, the polyether type or the polyester type of the polyol type which forms the skeleton of the urethane resin means that the repeating component of each ether and the component of the repeating unit of the ester are the main polyol components. The term "mainly" as used herein means 50% by mass or more based on the total mass of the polyol.

The weight average molecular weight of the anionic urethane resin (U) used in the basic organic-inorganic composite coating material is preferably from 100,000 to 200,000. The molecular weight of the urethane resin has a great impact on the physical properties of the membrane. ring. The low molecular weight substance causes low Tg and low mechanical properties as a plasticizer in the film, and as a result, various types of film properties such as corrosion resistance, solvent resistance, and chemical resistance are lowered. Further, the weight average molecular weight affects the volume of the urethane resin occupies in the basic organic-inorganic composite coating layer, and the basic organic-inorganic composite coating layer becomes larger as the weight average molecular weight of the urethane resin becomes larger. The volume of the occupied urethane resin becomes large. As a result, high Tg and high physical properties are obtained, and good film properties are exhibited.

Here, the weight average molecular weight of the anionic urethane resin (U) of the present embodiment and the raw material described below, and the weight average molecular weight described in the present specification are based on JIS-K7252-4. The measured value of size exclusion chromatography.

An anionic urethane resin (U) capable of being a polyisocyanate (particularly a diisocyanate); a polyol (particularly a diol); a carboxylic acid or sulfonic acid having 2 or more, preferably 2 hydroxyl groups or These reactive derivatives; and polyamines (especially diamines) are obtained as raw materials and obtained by a usual synthesis method. More specifically, but not to be construed as limiting, for example, a urethane prepolymer having an isocyanate group at both ends can be produced from a diisocyanate and a diol, and can be made with a carboxylic acid having 2 hydroxyl groups or The reactive derivative is reacted to form a derivative having an isocyanate group at both ends, and then a tertiary amine such as triethanolamine is added to form an ionic polymer (triethanolamine salt), and then added to water to form an emulsion, which is further added. The diamine is subjected to chain extension to obtain an anionic urethane resin (U).

The polyisocyanate used in the production of the anionic urethane resin (U) may be any of aliphatic, alicyclic and aromatic polyisocyanates. Specific examples thereof include tetramethylene diisocyanate, hexamethylene diisocyanate, leucine diisocyanate, hydrogenated deuterated diisocyanate, 1,4-cyclohexyl diisocyanate, and 4,4'-. Dicyclohexylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, 1,5 -naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenyl Methane diisocyanate, phenyl diisocyanate, decyl diisocyanate, tetramethylene decyl diisocyanate, and the like. Among these, tetramethylene diisocyanate, hexamethylene diisocyanate, quaternary acid diisocyanate, hydrogenated deuterated diisocyanate, 1,4-cyclohexyl diisocyanate, 4,4'-bicyclic ring are used. Hexyl methane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, 1,6-hexane diisocyanurate (trimer), carbodiimidized diisocyanate When an aliphatic or alicyclic polyisocyanate is obtained, it is preferable because a film excellent in corrosion resistance, heat yellowing resistance, moldability, and the like can be obtained.

As the type of the polyol used in the production of the anionic urethane resin (U), a polyether polyol or a polyester polyol is used. When the polyether or polyester skeleton is in contact with a strongly alkaline or strongly acidic aqueous solution, the bond is not easily broken, and it is important to obtain chemical resistance and corrosion resistance after alkali degreasing.

Used as a polyether polyol or polyester polyol Examples of the diol component include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, and 2-butyl-2-ethyl-1,3- Propylene glycol, 1,4-butanediol, neopentyl glycol, 3-methyl-2,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 3-methyl-1 , 5-pentanediol, 2-methyl-2,4-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptane Aliphatic alcohols such as alcohol, 3,5-heptanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol a diol; an alicyclic diol such as cyclohexane dimethanol or cyclohexane diol; and trimethylolethane, trimethylolpropane, hexitol, pentitol, glycerin, polyglycerin, new A trihydric or higher polyhydric alcohol such as pentaerythritol, dipentaerythritol or tetramethylolpropane.

Examples of the polyether polyols include 1,2-propanediol and 1,3-propanediol; the aforementioned low molecular polyols such as trimethylolpropane, glycerin, polyglycerin, and neopentyl alcohol; and bisphenol. A, an ethylene oxide and/or a propylene oxide adduct such as an amine compound such as ethylenediamine; or a polytetramethylene ether glycol. The weight average molecular weight of the polyether polyol used in the present embodiment is preferably from 300 to 5,000, particularly preferably from 1,000 to 3,000.

Examples of the polyester polyol include polyhydric alcohols such as low molecular weight polyols; and ester-forming derivatives derived from polycarboxylic acids, esters, anhydrides thereof, and/or their carboxylic acid halides, which are less than stoichiometric amounts thereof. And/or γ-caprolactone, δ-caprolactone, ε-caprolactone, dimethyl-ε-caprolactone, δ-valerolactone, γ-valerolactone, γ-butyrolactone The lactones and/or their direct hydrolysis reaction and/or transesterification reaction of the hydroxycarboxylic acid obtained by the hydrolysis ring-opening reaction are obtained. Examples of the polyvalent carboxylic acid or an ester-forming derivative thereof include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and pimelic acid. Suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, 2-methylsuccinic acid, 2-methyladipate, 3-methyladipate, 3-methylglutaric acid, 2 - aliphatic dicarboxylic acids such as methyl suberic acid, 3,8-dimethylsebacic acid, 3,7-dimethylsebacic acid, hydrogenated dimer acid, dimer acid, etc.; An aromatic dicarboxylic acid such as an acid, isophthalic acid or naphthalene dicarboxylic acid; an alicyclic dicarboxylic acid such as cyclohexane dicarboxylic acid; 1,2,4-benzenetricarboxylic acid and 1,3,5-benzene A tricarboxylic acid such as a formic acid or a terpolymer of a castor oil fatty acid; or a polycarboxylic acid such as a tetracarboxylic acid such as pyroic acid. Examples of the ester-forming derivative of the polyvalent carboxylic acid include such an acid anhydride, a chloride of the polyvalent carboxylic acid, a carboxylic acid halide such as a bromide, and a methyl ester, an ethyl ester or a propyl ester of the polyvalent carboxylic acid. A lower aliphatic ester such as isopropyl ester, butyl ester, isobutyl ester or amyl ester.

The carboxylic acid and/or sulfonic acid used in the production of the anionic urethane resin (U) having a carboxyl group or a salt thereof, and the reactive derivatives thereof are used in an anionic urethane resin ( U) is used to introduce an acidic group and to impart water dispersibility to the anionic urethane resin (U). The anionic group is neutralized by using a neutralizing agent to impart dispersibility to water. A polyalkanol group such as dihydroxy ^- methylpropionic acid, dimethylolbutanoic acid, dimethylolpentanoic acid, dimethylolhexanoic acid or 1,4-butanediol-2-sulfonic acid can be exemplified. Organic acids (such as dimethylol alkanoic acid) (such as carboxylic acids, sulfonic acids). Further, examples of the reactive derivative include hydrolyzable esters such as acid anhydrides. As described above, the anionic urethane resin (U) is self-dispersible in water, and a film excellent in corrosion resistance can be obtained without using or using an emulsifier as much as possible. Among these, dimethylolpropionic acid and dimethylolbutanoic acid are preferred. These carboxylic acids and sulfonic acids can be used singly or in combination of several kinds.

A polyamine, water, or the like can be used in the production of the anionic urethane resin (U). The polyamine, water, or the like can be used as a chain extender as a prepared prepolymer. These polyamines can usually be appropriately selected from the polyamines to be used. Examples of the polyamine to be used include ethylenediamine, propylenediamine, hexamethylenediamine, toluenediamine, and piperazine. 2-methylperazine Such as low molecular diamines; polyoxypropylene diamines, polyoxyethylene diamines and the like polyether diamines; Diamine (menthene diamine), isophorone diamine, norbornene diamine, bis(4-amino-3-methyldicyclohexyl)methane, diaminodicyclohexylmethane, bis(aminomethyl) An alicyclic diamine such as cyclohexane or 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro(5,5)undecane; Methylamine, α-(m-/p-aminophenyl)ethylamine, m-phenylenediamine, diaminodiphenylmethane, diaminodiphenyl hydrazine, diaminodiethyldimethylmethane, Aromatic di-diethyldiphenylmethane, dimethylthiotoluenediamine, diethyltoluenediamine, α,α'-bis(4-aminophenyl)-p-diisopropylbenzene Polyamines such as amines; and diterpene succinate, diammonium adipate, diterpene sebacate, diterpene bismuth, hydrazine hydrate, 1,6-hexamethylene double (N, N Anthraquinones such as -dimethylureido), 1,1,1',1'-tetramethylene-4,4'-(methylene-di-p-phenylene)diurea . These chain extenders can be used singly or in combination of several kinds.

The anionic urethane resin (U) may be a decane modified by a hydrolyzable decane compound at the stage of synthesis. The type and amount of the decane compound to be subjected to decane modification are not particularly limited. As the decane compound, a well-known decane coupling agent can be used. Anionic urethane resin (U) and anti-reaction by decane modification The adhesion of the basement membrane layer (interlayer adhesion) is increased, and it is associated with an increase in the compactness of the topcoat film. Thereby, the corrosion resistance and the moldability after the degreasing of the processed portion and the alkali are improved.

The anionic urethane resin (U) is preferably formulated in advance to form a film-forming auxiliary agent in order to improve the stability of the resin during the synthesis or the film formation property in the case where the surrounding environment at the time of film formation is low-temperature drying. Examples of the film-forming auxiliary agent include butyl glycol, N-methyl-2-pyrrolidone, butyl carbitol, and 2,2,4-trimethyl-1,3 pentanediol. Texanol or the like is preferably N-methyl-2-pyrrolidone.

(ingredient V: alkali citrate)

The alkaline organic-inorganic composite coating agent of the present embodiment uses alkali citrate (V) as a raw material. In general, alkali citrate (V) is a very water-soluble component. However, when it comes into contact with a metal ion other than an alkali metal, a salt which is insoluble to water is formed. For example, a salt which is insoluble to water can be formed with a metal ion such as Mg or Ca of an alkaline earth metal. Further, similarly to the above-mentioned organic titanium compound, a salt which is insoluble to water is formed in the same manner. In other words, it forms a salt which is insoluble to water by contact with the hydrofluoric acid zirconium hydroxide, the magnesium compound contained in the acidic inorganic inorganic coating layer of the lower layer, and the organic titanium compound contained in the upper alkaline organic-inorganic composite coating layer. Therefore, the surface-treated zinc-based plated steel sheet of the present embodiment exhibits excellent corrosion resistance.

When the test piece is exposed to a corrosive environment, it is strongly alkaline by dissolving oxygen under the film for reduction reaction. However, since the surface-treated zinc-based plated steel sheet of the present embodiment maintains a relatively high alkalinity under the film by the added alkali silicate, it is possible to suppress an excessive pH rise by the buffering action. Therefore, when the surface treatment agent of the present embodiment is used, even if the zinc basis weight on one side is 1 to 15 g/m ² less than before, excellent corrosion resistance can be obtained in the damaged portion and the end surface portion, and at the same time, after a long period of time, The surface-treated zinc-based plated steel sheet having a zinc basis weight of 20 g/m ² or more can suppress the occurrence of red rust by the same or more.

The alkali silicate (V) used in the present embodiment is preferably in the range of 4 to 1 in terms of SiO ₂ /Na ₂ O. Preferably, the SiO ₂ /Na ₂ O is 4 to 2. When SiO ₂ /Na ₂ O is more than 4, the viscosity becomes extremely high, resulting in deterioration of workability. When SiO ₂ /Na ₂ O is less than 1, sufficient damage resistance of the damaged portion and end surface corrosion resistance cannot be obtained.

In the alkali silicate (V) used in the present embodiment, the mass ratio (V) / (U) of the solid content of the component (U) to the component (V) is preferably 0.01 to 1. Preferably, (V) / (U) is from 0.02 to 0.5. More preferably 0.05 to 0.3. The best is (V) / (U) is 0.1 to 0.2. When (V)/(U) is more than 1, the basic organic-inorganic composite coating layer is brittle, and the corrosion resistance and moldability of the processed portion are deteriorated. When it is less than 0.01, sufficient damage of the damaged portion and the end face cannot be obtained. When the basic organic-inorganic composite coating layer is used, it is also constituted by using the mass ratio of the solid components described above.

(ingredient W: titanium alkoxide)

The basic organic-inorganic composite coating agent of the present embodiment uses titanium alkoxide (W) as a raw material. By using the titanium alkoxide (W), the carbon dioxide present in the skeleton of the anionic urethane resin (U) and the carbon dioxide present in the skeleton of the water-soluble carbodiimide resin (X) are utilized. The metal-crosslinking of the amine group enables densification of the basic organic-inorganic composite coating layer. Thereby, a dense film can be formed and Corrosion resistance and chemical resistance after alkali degreasing. Moreover, the corrosion resistance of the processed portion is improved by the rust-preventing effect derived from the titanium alkoxide (W) itself. Further, by forming a salt which is insoluble to water with the alkali silicate (V), a coating layer having a higher barrier property is formed.

The titanium alkoxide (W) has a structure in which an alkoxy group is coordinated around a titanium atom. Such a compound is easily hydrolyzed in water and condensed. Therefore, it is presumed that the titanium alkoxide (W) forms a plurality of oligomers or polymers which are condensed in water. The titanium alkoxide (W) used in the present application is preferably an alkoxy group and a chelating agent. Specific examples thereof include titanium tetraisopropoxide, titanium tetra-n-butoxide, titanium butoxide butoxide, titanium tetra-2-ethylhexoxide, titanium diisopropoxy acetonate, and tetraethyl hydrazine. Acetone titanium, dioctyloxybis-extension octyl glycolate, titanium diisopropoxy bisethylacetate pyruvate, titanium diisopropoxy bistriethanolamine, titanium ammonium propionate, propionic acid Titanium, titanium polyhydroxystearate, and the like. Particularly preferred are titanium diisopropoxy bisethylacetate pyruvate, titanium diisopropoxy bistriethanolamine and the like.

The basic organic-inorganic composite coating material of the present embodiment is a solid content ratio (w)/(V) of the metal contained in the component (W), that is, titanium (w) and the component (V), in an amount of 0.01 to 1. It is better. Preferably, (w) / (V) is from 0.03 to 0.8. More preferably, (w) / (V) is from 0.06 to 0.6. The best is (w) / (V) is 0.1 to 0.5. When (w)/(V) is more than 1, sufficient corrosion resistance, solvent resistance, and coating adhesion after alkali degreasing cannot be obtained, and sufficient stability of the basic organic-inorganic composite coating material cannot be obtained. When (w) / (V) is less than 0.01, the effect of improving corrosion resistance, solvent resistance, and corrosion resistance of the processed portion after alkali degreasing cannot be sufficiently obtained.

(ingredient X: polycarbodiimide resin)

The basic organic-inorganic composite coating agent of the present embodiment uses a water-soluble carbodiimide resin (X) as a raw material. Here, the water-soluble carbodiimide resin (X) serves as an organic crosslinking agent with a carboxylic acid present in the skeleton of the anionic urethane resin (U). Thereby, a dense film can be formed and the corrosion resistance and chemical resistance after alkali degreasing can be improved. Further, since the carbodiimide group having a relatively high polarity is introduced into the top coat layer, it is also very useful for coating adhesion.

The carbodiimide resin of the polycarbodiimide resin (X) is a polymer having a -N=C=N- group in the molecule, and can be, for example, in the presence of a carbodiimide catalyst. Manufactured by decarbonation condensation reaction of isocyanate. Here, examples of the carbodiimide catalyst include a combination of tin, magnesium oxide, potassium ion, 18-crown-6, and 3-methyl-1-phenyl-2-cyclophosphene oxide. . As the diisocyanate, a diisocyanate which is exemplified as the polyisocyanate is exemplified in the production of the anionic urethane resin (U).

The polycarbodiimide resin (X) is an aqueous polycarbodiimide resin, and is not particularly limited, and is dispersed or dissolved in water. The water-dispersible polycarbodiimide resin is a particle which can be clearly detected using a particle size distribution measuring apparatus (trade name PAR-III manufactured by Otsuka Electronics Co., Ltd.). On the other hand, the water-soluble polycarbodiimide resin is a particle which is detected to a very small extent by the particle size distribution measuring apparatus at the detection limit.

The carbodiimide equivalent of the polycarbodiimide resin (X) (the chemical formula amount of the carbodiimide group per 1 mol of the carbodiimide resin, in other words, The molecular weight of the carbodiimide resin divided by the number of carbodiimide groups contained in the carbodiimide resin is not particularly limited, and is preferably in the range of 100 to 1,000, and in the range of 300 to 700. good.

In the basic organic-inorganic composite coating material of the present embodiment, the solid content ratio of the component (X) to the component (U) is preferably (X) / (U) = 0.001 to 0.5. Preferably, (X) / (U) is from 0.005 to 0.4. More preferably, (X) / (U) is from 0.01 to 0.3. The best is 0.02 to 0.2. When (X) / (U) is more than 0.5, the corrosion resistance is deteriorated. When (X) / (U) is less than 0.001, sufficient coating adhesion cannot be obtained. The basic organic-inorganic composite coating layer is also blended using the mass ratio of the solid components described above.

(ingredient Y: decane coupling agent)

The basic organic-inorganic composite coating agent of the present embodiment uses a decane coupling agent (Y) as a raw material. The decane coupling agent (Y) has a fluorene atom as a center and an alkoxy group and an organic functional group. The alkoxy group bonded directly to the ruthenium atom is readily hydrolyzed in water to provide a stanol group. Because of the unstable functional group of the stanol group, a dehydration condensation is formed to change to a thermodynamically stable siloxane linkage. The polymerized oxime and the remaining stanol group are adsorbed on the substrate, and by interacting with the constituent components of the basic organic-inorganic composite coating layer, a film excellent in toughness and adhesion can be formed. As described above, the decane coupling agent (Y) used in the present embodiment contributes to the adhesion to the acidic inorganic coating layer by the stanol group. Further, a dense film is formed by interacting with a component derived from an anionic urethane resin (U) or an alkali silicate (V) added to an alkaline organic-inorganic composite coating agent. Therefore, excellent corrosion resistance is exhibited.

The decane coupling agent (Y) to be used in the present embodiment is not particularly limited, and examples thereof include the following. Examples thereof include vinyl trimethoxy decane, vinyl triethoxy decane, γ-aminopropyl trimethoxy decane, γ-aminopropyl ethoxy decane, and N-[2-(vinylbenzylamino). Ethyl]-3-aminopropyltrimethoxydecane, γ-methylpropenyloxypropylmethyldimethoxydecane, γ-methylpropenyloxypropyltrimethoxydecane, γ-甲Acryloxypropylmethyldiethoxydecane, γ-methylpropenyloxypropyltriethoxydecane, γ-glycidoxypropyltriethoxydecane, γ-epoxy Propoxypropylmethyldiethoxydecane, γ-glycidoxypropyltrimethoxydecane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxydecane, N-β ( Amine ethyl) γ-aminopropyltrimethoxydecane, N-β-(aminoethyl)-γ-aminopropyltriethoxydecane, N-β-(aminoethyl)-γ-amine cyclopropane Methyl dimethoxy decane, N-phenyl-γ-aminopropyl trimethoxy decane, γ-hydrothiopropyltrimethoxy decane, and the like. The decane coupling agent (Y) may be used singly or in combination of two or more.

The basic organic-inorganic composite coating material of the present embodiment is preferably a solid content ratio of the decane coupling agent (Y) to the component (U), and is preferably (Y) / (U) = 0.001 to 0.5. Preferably, (Y) / (U) is from 0.005 to 0.3. More preferably, (Y) / (U) is from 0.01 to 0.2. The best is 0.02 to 0.1. When (Y) / (U) is more than 0.5, the stability of the coating agent is low. When (Y)/(U) is less than 0.001, the effect of the decane coupling agent (Y) cannot be exhibited, and the film performance of any of corrosion resistance, chemical resistance, solvent resistance, and coating adhesion is lowered.

(ingredient Z: water-dispersible wax)

The water-dispersible wax (Z) used in the present embodiment is for imparting a coating to the coating layer. It is contained in the pre-slip property and improves the moldability. The average particle diameter is preferably in the range of 0.05 to 1.0 μm, preferably 0.1 to 0.6 μm. When the average particle diameter of the water-dispersible wax is more than 1.0 μm, the dispersion stability of the wax is deteriorated. When the average particle diameter of the water-dispersible wax is less than 0.05 μm, sufficient moldability cannot be obtained. Here, the particle diameter of a polyethylene wax means the average particle diameter measured by the particle size distribution measuring apparatus.

The molecular weight and melting point of the water-dispersible wax (Z) are not particularly limited, and the acid value is preferably in the range of 5 to 50, and preferably in the range of 10 to 30. When the acid value is less than 5, since the wax is almost incompatible with the resin, the wax is completely aligned on the surface of the film at the time of formation of the film, and it is easy to be separated from the top coat layer and the molding processability is lowered, which is not preferable. On the other hand, when the acid value is more than 50, since the hydrophilicity of the wax becomes strong, the slipperiness of the wax body is low, and the damage resistance is low, which is not preferable. The water-dispersible wax (Z) is usually an aqueous dispersion prepared by using a surfactant as a dispersing agent. The method of dispersing the water-dispersible wax is not particularly limited and may be in accordance with a method used in the industry.

The acid value of the water-dispersible wax (Z) can be obtained by the following method. A predetermined amount of the sample is dispensed and dissolved in an organic solvent. The phenolphthalein indicator was added to the liquid diluted with the organic solvent and titrated using a 0.1 N KOH ethanol solution. The acid value is obtained according to the following formula.

Acid value = 56.11 × specified concentration × titration / separation of sample weight

The basic organic-inorganic composite coating material of the present embodiment preferably has a mass ratio (Z)/(U) of the component (Z) to the component (U) of from 0.01 to 0.2. Preferably, (Z) / (U) is from 0.02 to 0.1. When (Z)/(U) is greater than 0.2, subject to The effect of the surfactant used in the water-dispersible wax causes the corrosion resistance to be low. When (Z) / (U) is less than 0.01, sufficient moldability cannot be obtained.

(ingredient: colloidal cerium oxide)

The alkaline organic-inorganic composite coating material composed of the components (U) to (Z) may also use colloidal cerium oxide as a raw material. The colloidal cerium oxide system serves as a task for adjusting fingerprint resistance and molding processability. The colloidal cerium oxide is an aqueous dispersion of a stanol group on the surface, and the particle size, shape, and type are not particularly limited, and the particle size is preferably in the range of 20 to 200 nm, and preferably 30 to 100 nm. Here, the particle diameter of cerium oxide refers to an average particle diameter measured by a particle size distribution measuring apparatus.

(ingredient: other optional ingredients)

The optional component of the basic organic-inorganic composite coating material of the present embodiment may be a filler, a surfactant, an antifoaming agent, a leveling agent, an antibacterial agent, a coloring agent, or the like, and may be added in a range that does not impair the performance of the film.

(ingredient: liquid medium)

The basic organic-inorganic composite coating agent of the present embodiment is an aqueous system. The term "water system" means that the solvent contains 60% or more of water as a main component. In order to adjust the drying property of the film, the viscosity of the coating agent, etc., it is also possible to use one or a combination of two or more kinds of one or more kinds of water-soluble organic substances such as a polyhydric alcohol, a ketone, or an ethylene glycol. Solvent.

(total concentration)

The solid content concentration of the basic organic-inorganic composite coating material of the present embodiment is preferably in the range of 5 to 30% by mass, and preferably 10 to 25% by mass in terms of the total solid content of each component. Solid formation The concentration is a concentration calculated from the mass of the residual solid component after drying the basic organic-inorganic composite coating material of the present form at about 100 °C.

(liquid)

The pH of the basic organic-inorganic composite coating material of the present embodiment is preferably in the range of 9 to 12. When it is necessary to adjust the pH, an alkaline substance such as ammonia, dimethylamine or triethylamine; or an acidic substance such as acetic acid, nitric acid or phosphoric acid can be added without impairing the effect range of the present embodiment. Further, the pH of the basic organic-inorganic composite coating material can also be adjusted by adding a metal salt such as Mg, Al or Zn.

<Modulation method of two doses>

The method for preparing the two coating agents (the acidic inorganic coating agent and the basic organic-inorganic composite coating agent) of the present embodiment is not particularly limited, and any of them can be produced by a conventionally known method. Here, a suitable example of the preparation method of the acidic inorganic coating material (L) will be described first. First, an aqueous solution obtained by adding an arbitrary amount of the zirconium compound (A) is prepared. In this case, as the zirconium compound (A), a fluorine-containing substance (such as zirconium fluoride) may be used, or a substance containing no fluorine may be used. When the fluorine-free zirconium compound (A) is used, a fluorine compound (E) (HF or the like) is further added as described later. Next, any amount of the magnesium compound (C) is added thereto and mixed. Further, in the aqueous solution, a water-dispersible cerium oxide (B), a vanadium compound (D), a compound containing a fluorine compound (E), and the like as necessary are added in an arbitrary amount and mixed. In this manner, it is possible to prepare a formulation in which the solid content concentration is a predetermined value and the components are dissolved or dispersed. Next, a suitable example of the method of adjusting the basic organic-inorganic composite coating material (M) will be described. First, an arbitrary amount of the component (U) is added to the deionized water, and an arbitrary amount of the component (V) is added and mixed. Subsequently, any amount of ingredients (W) is added and mixed. An arbitrary amount of the component (X) is added and mixed, and an arbitrary amount of the component (Y) is added and mixed, and an arbitrary amount of the component (Z) is added and mixed, and finally adjusted so as to become a predetermined solid component concentration. By doing so, it is possible to obtain a formulation in which the solid content concentration is a predetermined value and the components are dissolved or dispersed.

<Substrate>

As the substrate used in the production method of the present embodiment, a zinc-based plated steel sheet is preferred from the viewpoint of use. Examples of the plating method of the zinc-based plated steel sheet include melt plating, electroplating, and vapor deposition plating. Although not particularly specified, zinc-based plating is preferably subjected to plating treatment.

<Application order of two doses>

The surface treatment layer (the acidic inorganic coating layer and the basic organic-inorganic composite coating layer) having the two-layer structure of the present embodiment can be dried and made alkaline organic and inorganic by contacting the acidic inorganic coating material with the zinc plating surface. The composite coating agent is brought into contact with the layer and dried. Hereinafter, each step will be described in detail.

<Acid inorganic coating layer forming step>

First, the step of forming an acidic inorganic coating layer will be described.

(cleaning step)

When oil or dirt adheres to the surface of the zinc-based plated steel sheet, after solvent degreasing, alkali degreasing, and acid degreasing, after washing with water to clean the surface, it is preferred to contact the coating agent acidic inorganic coating agent. It is also possible to dry it after washing as needed.

(contact step)

The manufacturing method of the present aspect is the zinc system after the cleaning step as described above. The surface of the plated steel sheet was brought into contact with the acidic inorganic coating material of the present embodiment as described above.

The method of bringing it into contact is not particularly limited, and for example, a previously known method can be applied. For example, a method of roll coating, curtain coating, air spray, airless spray, dipping, bar coating, and brush coating can be applied. Further, before the acidic inorganic coating material of the present embodiment is brought into contact with the surface of the zinc-based plated steel sheet by such a method, hot water washing, alkali degreasing, and surface treatment may be applied to the zinc-based plated steel sheet as needed in other production lines. Adjust the usual pre-processing.

(drying step)

In the production method of the present embodiment, the acidic inorganic coating material of the present embodiment is dried by contacting the surface of the zinc-based plated steel sheet by the method described above. The drying method is also not particularly limited, and for example, a previously known method can be applied. For example, a method using a blowing method or a dryer (an oven or the like) can be mentioned. The drying temperature and the drying time are not particularly limited as long as the drying method is carried out using a dryer. For example, the highest temperature of the surface of the zinc-based plated steel sheet can be set to 60 to 120 ° C and dried for about 1 to 120 seconds.

<Alkaline organic-inorganic composite coating layer forming step>

Next, the step of forming an alkaline organic-inorganic composite coating layer will be described.

(contact step)

In the production method of the present embodiment, the basic organic-inorganic composite coating material of the present embodiment described above is brought into contact with the surface of the acidic inorganic coating layer formed as described above.

The method of bringing it into contact is not particularly limited, and for example, a previously known method can be applied. For example, a method of roll coating, curtain coating, air spraying, airless spraying, dipping, bar coating, and brush coating can be employed.

(drying step)

In the production method of the present embodiment, the basic organic-inorganic composite coating material of the present embodiment is dried by using the surface of the acidic inorganic coating layer after contacting the surface as described above. The method of drying is also not particularly limited, and for example, a previously known method can be applied. The drying temperature and the drying time are not particularly limited as long as the drying method is carried out using a dryer. For example, the highest temperature of the surface of the zinc-based plated steel sheet on which the acidic inorganic coating layer is formed can be set to 100 to 180 ° C, and dried. 1 to 120 seconds or so. The preferred maximum temperature is from 120 to 150 °C.

"Structure and Properties of Surface Treatment Zinc Plated Steel Plate" <layer composition>

The surface-treated zinc-based plated steel sheet of the present embodiment is a two-layered film having an acidic inorganic coating layer and an alkaline organic-inorganic composite coating layer. Here, from the viewpoint of performance balance, the present embodiment is preferably a two-layered film-treated zinc-based plated steel sheet formed by coating and coating a two-layered film, wherein the two-layered acidic inorganic coating layer is a lower layer and an alkaline organic inorganic layer. The composite coating layer is the upper layer. The alkaline organic-inorganic composite coating layer preferably contains a water-dispersible wax (Z).

<film weight>

The film weight of the present embodiment can be appropriately determined depending on the use and the like. However, the range of the dry film weight of the surface-treated zinc-based plated steel sheet which is composed of the two layers of the acidic inorganic coating layer and the basic organic-inorganic composite coating layer, which is the best effect of the present embodiment, is an acidic inorganic coating layer. It is preferably 0.01 to 0.5 g/m ² , more preferably 0.03 to 0.3 g/m ² . Particularly preferred is 0.05 to 0.2 g/m ² . When the film weight is less than 0.01 g/m ² , it is disadvantageous in terms of corrosion resistance and moldability. When the film weight is more than 0.5 g/m ² , in terms of productivity, not only the cost becomes high, but also the film properties such as coating adhesion and solvent resistance are low. In the basic organic-inorganic composite coating layer, the film weight is preferably from 0.5 to 3 g/m ² , preferably from 0.7 to 2 g/m ² . It is particularly preferably from 0.8 to 1.5 g/m ² . When the dry film weight is less than 0.5 g/m ² , the corrosion resistance, the damaged portion and the end surface corrosion resistance, the chemical resistance, the moldability, and the fingerprint resistance are lowered. On the other hand, when the film weight is more than 3.0 g/m ² , heat-resistant yellowing, electrical conductivity, and paintability are low, and the cost is also high.

<properties>

The surface-treated zinc-based plated steel sheet of the present embodiment is excellent in balance of properties, and has good corrosion resistance, solvent resistance, moldability, electrical conductivity, and coating property in any of the flat portion, the alkali degreasing, and the processed portion. The damage portion and the end face are excellent in corrosion resistance, and red rust does not easily occur over a long period of time. Further, the glass transition temperature of the basic organic-inorganic composite coating layer is preferably 100 ° C or higher. The coating layer of the topcoat (upper side) having a glass transition temperature of less than 100 ° C is liable to cause physical property changes in an actual use environment. The reason for this is that the cohesive force in the film is insufficient and sufficient barrier properties cannot be obtained. However, when the glass transition temperature is 100 ° C or more, since the cohesive force becomes high, the barrier property of the film is improved. Needless to say, of course, the high Tg of the film is derived from the anionic urethane resin (U). This can be achieved by a method of changing to a short-chain polyol, increasing the amount of branching, and increasing the urethane group.

"Use of Surface Treatment Zinc Plated Steel Plate"

The combination of the acidic inorganic coating layer and the basic organic-inorganic composite coating layer of the present embodiment is not particularly limited, and a zinc-based plated steel sheet having a zinc basis weight of 1 to 15 g/m ² on one side is used and is required to be resistant. Fingerprint steel sheets (fingerprint resistant steel sheets) are preferred. The surface-treated zinc-based plated steel sheet of the present embodiment has excellent corrosion resistance, coating adhesion, solvent resistance, and heat-resistant yellowing resistance, and is excellent in moldability. Since the surface-treated zinc-based plated steel sheet having a zinc basis weight of 20 g/m ² or more can maintain the corrosion resistance of the damage portion and the end portion of the same or more, the film performance is not lowered, and Zinc-coated steel sheets are treated with a surface that is effective in the use of the environment and resources.

"Other forms of surface-treated zinc-based plated steel sheets" (layering order of the coating layer)

In the surface-treated zinc-based plated steel sheet of the present invention, the order of lamination of the acidic inorganic coating layer and the basic organic-inorganic composite coating layer may be different from the above-described embodiment. In other words, an alkaline organic-inorganic composite coating layer may be formed as a lower layer on the surface of the zinc-based plated steel sheet, and an acidic inorganic coating layer may be formed as the upper layer. However, in order to more effectively exhibit various properties obtained by the above-described acidic inorganic coating layer and basic organic-inorganic composite coating layer, the above layer is an acidic inorganic coating layer and the upper layer is an alkaline organic-inorganic composite coating. The layer is better.

(application method of two doses)

In addition, the acidic inorganic coating material and the basic organic-inorganic composite coating material described above are "coating type coating agents", but may be as described above. "Coating agent other than coating type" having different forms.

In general, the surface coating agent of a general metal material has a reaction type (self-precipitation type, electro-analytical type, etc.) in addition to a coating type. In addition to the coating type, for example, after the coating agent is brought into contact with the surface of the metal material (zinc-based plated steel sheet) of the above-mentioned substrate, it is usually subjected to a water washing treatment and then dried. This is because the film formed by contacting the coating agent with the surface of the metal material contains unnecessary components (or components for lowering the performance) for achieving the desired properties, so that it is removed by water washing. good. The "coating type coating agent" of the coating material of the above-described embodiment may be subjected to such a water washing treatment, but it is not necessarily required to form a film which can achieve desired properties without being subjected to a water washing treatment (however, It can be washed before drying). On the other hand, the "coating agent other than the coating type" is preferably subjected to such a water washing treatment, and when the water washing treatment is performed, a film capable of achieving the desired performance can be formed, and when the water washing treatment is not performed, only the formation cannot be achieved. The performance required, or the performance of the film.

Therefore, the coating agent of the present embodiment preferably contains a component (nitrate, sulfate, or the like) which has a possibility of deteriorating the properties of the film as much as possible.

[Examples]

Hereinafter, the effects of the present invention will be specifically exemplified using the examples and comparative examples. The examples are merely illustrative of the invention, and the invention is not limited at all. In the examples, % means mass% unless otherwise specified.

[Manufacture of test panels] (1) Test board

A zinc plated steel sheet having a plate thickness of 0.8 mm (zinc adhesion amount of 10 g/m ² and 20 g/m ² per side) was used.

(2) Degreasing

Alkali degreasing is performed to remove the dirt of the test plate. Specifically, the alkali degreaser PALGLIN N364S (manufactured by Nippon Parkerzing Co., Ltd.) was adjusted to a concentration of 20 g/L using deionized water, and spray treatment was carried out at a temperature of 60 ° C for 10 seconds. Subsequently, after washing with tap water, extrusion was carried out using a water removal roller and hot air drying was carried out at 50 ° C for 30 seconds.

(3) Preparation and coating method of acidic inorganic coating agent

First, an aqueous solution prepared by adding an arbitrary amount of the zirconium compound (A) is prepared. Next, any amount of the magnesium compound (C) is added thereto and mixed. Further, a compound containing water-dispersible ceria (B), a vanadium compound (D), an optional fluorine compound (E), or the like is added to the aqueous solution and mixed. It can be obtained by dissolving or dispersing, and finally, the acidic inorganic coating agent shown in Table 1 is prepared so that the solid content concentration is 3%. The dry film weight of the acidic inorganic coating layer was adjusted by adjusting the solid content concentration by diluting the acidic inorganic coating material, or changing the type of the bar coater to have the film weight shown in Table 1. One side of the zinc plated steel sheet was coated with a bar coater and heated and dried using a hot air drying oven to reach a predetermined plate temperature.

(4) Modification and coating method of alkaline organic-inorganic composite coating agent

Anionic urethane resin (U), alkali citrate (V), titanium alkoxide (W), polycarbodiimide resin (X), decane coupling agent (Y), water-dispersible wax (Z) The alkaline organic-inorganic composite coating agent shown in Table 2 was produced. Out of Any amount of anionic urethane resin (U) is added to the water. Further, any amount of alkali citrate (V) is added and mixed. Subsequently, any amount of titanium alkoxide (W) is added and mixed. Any amount of polycarbodiimide resin (X) is added and mixed. Any amount of decane coupling agent (Y) is added and mixed. Any amount of water-dispersible wax (Z) is added and mixed. The adjustment was made so that the final solid content concentration was 16%. The dry film weight of the basic organic-inorganic composite coating layer was adjusted by adjusting the solid content concentration by diluting the above-mentioned basic organic-inorganic composite coating material, or changing the type of the bar coater to obtain the film weight shown in Table 2. One side of the test plate on which the acidic inorganic coating layer was formed was applied using a bar coater, and dried at a predetermined plate temperature using a hot air drying oven.

(5) Raw materials of acidic inorganic coating materials Zirconium compound (A)

(A1) Zirconium hydrofluoride (manufactured by Morita Chemical Industry, trade name, zirconium hydrofluoride 40%)

(A2) Zirconium carbonate (made by Japan Light Metal, trade name Basic Zirconium Carbonate)

(A3) Zirconium hydroxide (manufactured by Japan Light Metal, trade name zirconium hydroxide)

Water-dispersible cerium oxide (B)

(B1) Colloidal cerium oxide, average particle size 20 μm (manufactured by Nissan Chemical Industry, product name SNOWTEX O)

(B2) Colloidal cerium oxide, average particle size 5 μm (manufactured by Nissan Chemical Industry, product name SNOWTEX NSX)

(B3) Colloidal cerium oxide, average particle size 50 μm (manufactured by Nissan Chemical Industry, product name SNOWTEX L)

Magnesium compound (C)

(C1) Magnesium oxide (made by Kyowa Chemical Industry Co., Ltd., trade name KYOWAMAG30)

(C2) Magnesium carbonate (manufactured by Kyowa Chemical Industry, trade name Industrial magnesium carbonate)

(C3) Magnesium hydroxide (manufactured by Kyowa Chemical Industry Co., Ltd., trade name KYOWASUIMAG F)

Vanadium compound (D)

(D1) Ethyl acetonide vanadium (manufactured by Emerging Chemical Industry, trade name acetonitrile acetone vanadium 50D)

(D2) Vanadium sulfate (manufactured by Emerging Chemical Industry, trade name vanadium sulfate)

(D3) Vanadium oxalate (manufactured by Sanjin and Chemicals, trade name vanadium oxalate (IV))

Fluorine compound other than zirconium hydrofluoride (E)

(E1) Hydrofluoric acid (manufactured by Morita Chemical Industry, trade name 55% hydrofluoric acid)

(E2) ammonium fluoride (manufactured by Morita Chemical Industry, trade name ammonium fluorozirconate)

(E3) Titanium hydrofluoride (manufactured by Morita Chemical Industry, trade name titanium hydrofluoride)

(6) Raw materials of alkaline organic-inorganic composite coating agent Anionic urethane resin (U)

(U1) Polyether-based water-dispersible urethane resin: glass transition temperature of 90 ° C, acid value of 5 (carboxyl: derived from dimethylolpropionic acid), weight average molecular weight of 100,000 (first industrial pharmaceutical manufacturing, trade name SUPERFLEX130)

(U2) Polyester-based water-dispersible urethane resin: glass transition temperature: 95 ° C, acid value of 15 (carboxyl: derived from dimethylolpropionic acid), weight average molecular weight of 100,000 (made by Adeka, trade name ADEKA BONTIGHTER HUX -320)

(U3) Polyester water-dispersible urethane resin: glass transition temperature: 130 ° C, acid value of 20 (carboxyl: derived from dimethylolpropionic acid), weight average molecular weight of 150,000 (manufactured by DIC, trade name HYDRAN WLS- 210)

Alkali citrate (V)

(V1) No. 4 sodium citrate (manufactured by Nippon Chemical Industry Co., Ltd., trade name: sodium citrate No. 4)

(V2) No. 3 sodium citrate (manufactured by Nippon Chemical Industry Co., Ltd., trade name J Sodium Hydrate No. 3)

(V3) As a comparative component which is not an alkali silicate, water-dispersible cerium oxide (manufactured by Nissan Chemical Industries, trade name SNOWTEX N)

Titanium alkoxide (W)

(W1) Titanium diisopropoxy acetoacetate (manufactured by Matsumoto Fine Chemical, trade name TC-100)

(W2) Titanium diisopropoxy bistriethanolamine (manufactured by Matsumoto Fine Chemical, trade name TC-400)

(W3) Titanium diisopropoxide dipropoxide (manufactured by Matsumoto Fine Chemical, trade name TC-315)

Carbodiimide resin (X)

(X1) carbodiimide equivalent 430 (produced by Nissin, trade name CARBODILITE SV-02)

(X2) carbodiimide equivalent 380 (produced by Nissin, trade name CARBODILITE V-02-L2)

(X3) As a comparative component which is not a carbodiimide resin, the isocyanate is blocked (manufactured by Daiichi Kogyo Co., Ltd. under the trade name Elastron BN-04)

Decane coupling agent (Y)

(Y1) γ-glycidoxypropyltrimethoxydecane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBM-403)

(Y2) Tetraethoxydecane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBE-04)

Wax (Z)

(Z1) polyolefin wax, particle size 0.2 μm (manufactured by Mitsui Chemicals, trade name CHEMIPEARL W950)

(Z2) polyolefin wax, particle size 0.3μm (manufactured by Mitsui Chemicals, trade name CHEMIPEARL W900)

(Z3) polyolefin wax, particle size 0.3μm (manufactured by Mitsui Chemicals, trade name CHEMIPEARL W401)

(7) Method for measuring physical properties and resin film physical properties of the basic organic-inorganic composite coating layer (A) of the obtained test material (a) Glass transition temperature (Tg)

The measurement was carried out using a dynamic viscoelasticity measuring apparatus (manufactured by RSAG2 Co., Ltd., TA INSTRUMENTS). Tan δ max is set as Tg.

[evaluation test]

A coating layer composed of one layer of components (A) to (E) or components (U) to (Z) on the surface of the test plate, and an acidic inorganic coating layer and an alkaline organic-inorganic composite coating layer The test panels formed by the layer structure were evaluated for performance as described below. The evaluation results of the respective examples and comparative examples are shown in Tables 3 and 4.

(7)-1 plane corrosion resistance

The salt spray test prescribed in JIS-Z2371:2000 was carried out for 240 hours, and the area ratio of white rust occurrence was visually evaluated.

<Evaluation criteria>

◎: The area ratio of white rust is less than 5%

○: White rust occurrence area ratio is 5% or more and less than 10%

○△: The area ratio of white rust is 10% or more and less than 30%.

△: The area ratio of white rust is 30% or more and less than 50%.

×: The area ratio of white rust is 50% or more

(7)-2 Corrosion resistance after alkali degreasing

The alkali degreaser PALGLIN N364S (manufactured by Parkerzing Co., Ltd., Japan) was adjusted to a concentration of 20 g/L using deionized water, and spray treatment (spray pressure: 0.5 kg/cm ² ) was carried out at a temperature of 60 ° C for 2 minutes. Subsequently, after washing with tap water, the water was squeezed using a water removal roller. Subsequently, a salt spray test in accordance with JIS-Z2371 was carried out for 240 hours, and the white rust occurrence area ratio was visually evaluated.

<Evaluation criteria>

◎: The area ratio of white rust is less than 5%

○: White rust occurrence area ratio is 5% or more and less than 10%

○△: The area ratio of white rust is 10% or more and less than 30%.

△: The area ratio of white rust is 30% or more and less than 50%.

×: The area ratio of white rust is 50% or more

(7)-3 Processing section corrosion resistance

6 mm extrusion processing was performed using an Erichsen tester (Erichsen tester), followed by a salt spray test in accordance with JIS-Z2371 for 240 hours, and the white rust occurrence area ratio was visually evaluated.

<Evaluation criteria>

◎: The area ratio of white rust is less than 5%

○: White rust occurrence area ratio is 5% or more and less than 10%

○△: The area ratio of white rust is 10% or more and less than 30%.

△: The area ratio of white rust is 30% or more and less than 50%.

×: The area ratio of white rust is 50% or more

(7)-4 Corrosion resistance of damaged parts

After cross cutting was performed using an NT cutter (A300 type manufactured by NT Co., Ltd.), a salt spray test according to JIS-Z2371 was carried out for 120 hours, and the maximum rust width on one side was visually evaluated.

<Evaluation criteria>

◎: rust width is less than 5mm

○: rust width 5mm or more and less than 7mm

○△: rust width 7mm or more and less than 8.5mm

△: rust width 8.5mm or more and less than 10mm

×: rust width 10mm or more

(7)-5 end face corrosion resistance

A salt spray test in accordance with JIS-Z2371 was carried out for 72 hours, and the rust width from the end surface was visually evaluated.

<Evaluation criteria>

◎: rust width is less than 10mm

○: rust width 10mm or more and less than 12mm

○△: The rust width is 12 mm or more and less than 13.5 mm.

△: The rust width is 13.5 mm or more and less than 15 mm.

×: rust width 15mm or more

(7)-6 red rust resistance

A salt spray test in accordance with JIS-Z2371 was carried out for 72 hours, and the area of occurrence of red rust generated from the end surface was visually evaluated.

<Evaluation criteria>

◎: Red rust occurrence area rate is 0%

○: The area ratio of red rust is 1% or more and less than 5%.

○ △: The area ratio of red rust occurrence is 5% or more and less than 10%.

△: The area ratio of red rust is 10% or more and less than 20%.

×: The area ratio of red rust is 20% or more

(8) Solvent resistance

Methyl ethyl ketone (MEK), ethanol, and hexane were permeated into the gauze, and the surface of the alkaline organic-inorganic composite coating layer of each test plate was subjected to a friction test for 20 times and the surface was observed.

<Evaluation criteria>

◎: no change in appearance

○: There are several changes

△: There is a slight change

×: There is a change

(9) Formability (die scratch resistance)

A test piece (with a thickness of 0.8 mm) cut into 30 mm × 150 mm was formed using a 200-ton crank press. The shape (the shoulder of the extrusion die and the punch R = 5 mm, the gap: the thickness of the plate - 20%), and the appearance of the molded article (the portion subjected to the sliding caused by the mold) was visually evaluated.

<Evaluation criteria>

◎: No change at all

○: Part of the micro-discoloration (can observe scratches)

△: Part of the discoloration (scratch is conspicuous),

×: Total discoloration (scratch is very conspicuous)

(10) Conductivity

Surface resistance tester (SQ meter / Yamazaki Seiki Institute) System) Evaluation of surface resistance. The pressing load was set to 300 g, the contact area was set to a diameter of 0.9 mm, and the operating speed was set to 10 mm/min.

<Evaluation criteria>

○: Surface resistance is less than 100Ω

△: The surface resistance is 100 Ω or more and less than 300 Ω.

×: The surface resistance is 300 Ω or more

(11) Coating adhesion

Referring to the old JIS K5400, spray coating was carried out using a melamine alkyd paint (GLIMIN #500 manufactured by Shinto Paint Co., Ltd.). Subsequently, baking was performed at 120 ° C for 20 minutes, and after drying, a 25 μm coating film was formed. Subsequently, 100 1 mm checkerboards were applied and tape peeling was performed.

<Evaluation criteria>

○: no peeling

△: The number of remaining checkerboards is 80 or more and less than 100

×: The number of remaining checkerboards is less than 80

(12) Fingerprint resistance

After measuring the hue of the predetermined portion (in the Hunter color system L1, a1, b1) using ZE2000 (Nippon Electric Color), Vaseline was coated here and KIMGIPE (trademark; wiping paper) was used (Tech-Jam Co., Ltd.)擦), and then measure the hue (L2, a2, b2) of the same part and evaluate the color difference at this time (ΔE=√{(L2-L1) ² +(a2-a1) ² +(b2-b1 ) ² }.

<Evaluation criteria>

○: △E is 1.5 or less

△: ΔE is greater than 1.5 and less than 2

×: ΔE is greater than 2

(13) Stability of the coating agent

Each of the acidic inorganic coating agent and the basic organic-inorganic composite coating agent was allowed to stand in a thermostat at 40 ° C for one month, and then the appearance was visually evaluated.

<Evaluation criteria>

○: No change in appearance

△: a little white turbid or trace precipitate

×: a large amount of precipitation or gelation

As can be seen from Table 3, the surface-treated zinc-based plated steel sheet coated in Example 2 exhibited superior performance compared to the surface-treated zinc-based plated steel sheet of the first coating, and the basis weight of the zinc was 20 g/%. For the steel of m ² , any evaluation item is equivalent or more. In other words, since the surface-treated steel sheets of the examples have the same film properties as those of the zinc-coated steel sheets having the previous zinc basis weight, the use amount of zinc can be suppressed while maintaining excellent quality. On the other hand, it was found that in the comparative example, one of them was inferior. Specifically, it is as follows. As shown in Table 4, Comparative Examples 1 to 5, Comparative Example 7, and Comparative Example 8 removed one of the components (A) to (E), resulting in a poor performance. Comparative Examples 9 to 12 and Comparative Examples 14 to 16 removed one of the components (U) to (Z), resulting in a poor performance. In Comparative Examples 17 to 22, the amount of the acidic inorganic coating layer and the basic organic-inorganic composite coating layer was out of the range of the invention, and it was not possible to satisfy various properties. Comparative Examples 23 and 24 are prior art, zinc units, in which the zinc basis weight of the steel material is the previous steel of 20 g/m ² and 10 g/m ² , and the component (E) is removed and the type of the component (V) is different. When the steel material having an area weight of 10 g/m ² is inferior to the performance of the surface-treated steel sheet of the example. In Comparative Examples 25 and 26, when the previous chemical treatment was carried out in the lower layer, the phosphate-based conductivity was insufficient, and even in the case of forming Zr, it was inferior to the performance of the surface-treated steel sheet of the example. Further, in Comparative Examples 17 and 18, although the film weight of the acidic inorganic coating layer was less than 0.01 g/m ² , the evaluation of the workability was excellent for the following reasons. The molding processability depends on the amount of the film of the upper layer (the basic organic-inorganic composite coating layer of the present embodiment), and the molding processability is improved because the amount of the film is large, and the comparative examples 17 and 18 are based on the alkaline organic-inorganic composite. The amount of coating on the coating is large.

Claims (8)

A surface-treated zinc-based plated steel sheet having a zinc plating layer on both surfaces of a steel sheet, and further comprising a two-layer film composed of an acidic inorganic coating layer and an alkaline organic-inorganic composite coating layer on the surface of the zinc plating layer The weight of the acidic inorganic coating layer is 0.01 to 0.5 g/m ² ; and the weight of the alkaline organic-inorganic composite coating layer is 0.5 to 3 g/m ² , wherein the acidic inorganic coating layer is added at least The acidic inorganic coating agent (L) having a pH of 2 to 5, which is a zirconium compound (A), a water-dispersible cerium oxide (B), a magnesium compound (C), a vanadium compound (D), and a fluorine compound (E), is coated. The layer formed; the alkaline organic-inorganic composite coating layer is an anionic urethane resin (U), an alkali citrate (V), a titanium alkoxide to which at least a weight average molecular weight of 100,000 to 200,000 is added. (W), a layer formed by coating a basic organic-inorganic composite coating material (M) having a pH of 9 to 12 and having a polycarbodiimide resin (X) and a decane coupling agent (Y). The surface-treated zinc-based plated steel sheet according to the first aspect of the invention, wherein the one surface of the zinc-based plated steel sheet has a zinc basis weight of 1 to 15 g/m ² . The surface-treated zinc-based plated steel sheet according to the first aspect of the invention, wherein the alkaline organic inorganic coating layer contains a water-dispersible wax (Z). The surface-treated zinc-based plated steel sheet according to the first aspect of the invention, wherein the anionic urethane resin (U) has a carboxyl group or a salt thereof. The surface-treated zinc-based plated steel sheet according to the third or fourth aspect of the invention, wherein the solid component of the metal (a) and the anionic urethane resin (U) contained in the zirconium compound (A) The mass ratio is (a) / (U) = 0.001 to 0.4; the mass ratio of the solid component of the water-dispersible cerium oxide (B) to the anionic urethane resin (U) is (B) / (U) = 0.001 to 1; the mass ratio of the metal (c) contained in the magnesium compound (C) to the solid content of the alkali silicate (V) is (c) / (V) = 0.001 to 0.5; the metal contained in the vanadium compound (D) (d) The mass ratio of the solid component to the alkali silicate (V) is (d) / (V) = 0.001 to 0.5; the fluorine element (e) of the fluorine compound (E) and the metal contained in the magnesium compound (C) The mass ratio of the solid component of (c) is (e) / (c) = 0.1 to 30; the mass ratio of the metal (w) contained in the titanium alkoxide (W) to the solid component of the alkali citrate (V) is ( w) / (V) = 0.01 to 1; the mass ratio of the solid content of the polycarbodiimide resin (X) to the anionic urethane resin (U) is (X) / (U) = 0.001 to 0.5; The mass ratio of the solid component of the decane coupling agent (Y) to the anionic urethane resin (U) is (Y) / (U) = 0.001 to 0.5; the water-dispersible wax (Z) and the anionic amine A Solid content by mass of polyester resin (U) ratio of (Z) / (U) = 0.01 to 0.2. The surface-treated zinc-based plated steel sheet according to any one of claims 1 to 4, wherein the alkaline organic-inorganic composite coating layer has a glass transition temperature of more than 100 °C. The surface-treated zinc-based plated steel sheet according to any one of claims 1 to 4, wherein the zinc-based plated steel sheet is a zinc-based plated steel sheet. Method for manufacturing surface-treated zinc-based plated steel sheet, which is included in steel The surface of the zinc-based plated steel sheet having the zinc-plated layer on both sides of the sheet, and the acidic inorganic coating layer and the basic organic-inorganic composite coating layer according to any one of the above claims 1 to 7 In the step of forming a two-layer film, the step of forming the two-layer film includes the step of forming an acidic inorganic coating layer, and applying the acidic inorganic coating (L) to the zinc-based plated steel sheet at 50 ° C or more and 100 ° C or less. The step of forming the basic organic-inorganic composite coating layer is carried out by coating the upper layer of the acidic inorganic coating layer and coating the basic organic-inorganic composite coating material (M), and then reaching at 100 ° C or more and less than 200 ° C. The temperature is dried.