JP5461115B2 - High corrosion resistance surface-treated steel sheet - Google Patents

Description

  The present invention relates to a highly corrosion-resistant surface-treated steel sheet that is optimal for applications such as automobiles, home appliances, and building materials, and particularly relates to an environment-friendly surface-treated steel sheet that does not contain hexavalent chromium in a coating film.

  Conventionally, for steel sheets for automobiles, steel sheets for household appliances, and steel sheets for building materials, hexavalent chromium is used for the purpose of improving corrosion resistance (white rust resistance, red rust resistance) on the surface of zinc-plated steel sheets or aluminum-based plated steel sheets. Steel plates that have been subjected to chromate treatment with a treatment liquid containing as a main component have been widely used. However, since chromate treatment uses hexavalent chromium, which is a pollution-controlling substance, recently there has been a movement to regulate its use. On the other hand, instead of chromate treatment, surface treatment technology that does not use hexavalent chromium at all is used. Development is actively underway. Among these, several techniques using an organic compound or an organic resin have been proposed, and examples include the following.

(1) Technology for forming a film from an aqueous resin composition obtained by reacting an epoxy resin with a hydrazine derivative having active hydrogen, a surface treatment composition containing a silane coupling agent, phosphoric acid, and the like (for example, Patent Document 1)
(2) A resin composition in which a composite oxide film containing fine oxide particles, phosphoric acid and a specific metal is formed as a lower layer, and an hydrazine derivative having active hydrogen is reacted with an organic resin such as an epoxy resin on the upper layer. Of forming an organic film with a coating composition containing a rust preventive additive and a specific anticorrosive additive (for example, Patent Document 2)
(3) Technology for forming a lower layer film composed of a titanium compound, an organic phosphate compound, a water-soluble resin, a vanadate and a zirconium salt, and forming a fingerprint-resistant film on the upper layer (for example, Patent Document 3)
In order to improve the curability of the epoxy resin constituting the organic film, the following techniques have been proposed.
(4) Technology for forming a film with a coating material comprising a titanium compound, an organic phosphoric acid compound, and inorganic phosphoric acid on a metal substrate (for example, Patent Document 4)

JP 2003-105554 A JP 2002-53979 A JP 2006-22370 A WO2003-37996

However, these conventional techniques have the following problems.
First, in the techniques (1) and (2), a dense organic polymer film (barrier layer) is formed by imparting a hydrazine derivative to an epoxy resin, thereby imparting desired corrosion resistance. Furthermore, the barrier property is reinforced by crosslinking using a curing agent such as polyisocyanate. However, with such an organic polymer film, it is difficult to ensure barrier properties over a long period of time and suppress corrosion. Moreover, when severe processing is applied to the steel sheet, a sufficiently satisfactory coating film performance cannot be obtained even if a high molecular weight epoxy resin is used.

On the other hand, although the technique (3) can provide a certain degree of corrosion resistance by the lower layer film, the adhesiveness is greatly inferior, and a peeling interface is formed between the plating film and the lower layer film.
The technique (4) is based on a titanium-containing aqueous solution and an organic acid, and allows the addition of inorganic phosphoric acid to improve the corrosion resistance. Then, it was found that there is a region where the adhesiveness is greatly inferior.

  Accordingly, an object of the present invention is to solve such a problem of the prior art, and is a surface-treated steel sheet that does not contain hexavalent chromium in the film, and is subjected to alkaline degreasing by a user or exposed to a corrosive environment for a long period of time. However, it is to provide a surface-treated steel sheet having excellent flat plate and post-processing corrosion resistance, and excellent adhesive bondability.

  As a result of intensive studies by the present inventors in order to solve the above problems, an organic phosphate compound and an inorganic phosphate compound with respect to a specific titanium-based aqueous liquid on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet The above-mentioned problem is solved by forming a film with a surface treatment composition in which a specific amount is added and further forming an upper film with a coating composition containing a specific high molecular weight epoxy group-containing resin on the upper layer. It has been found that very excellent corrosion resistance and adhesive bondability can be obtained.

The present invention has been made on the basis of such knowledge and has the following gist.
[1] At least one selected from a hydrolyzable titanium compound, a hydrolyzable titanium compound low-condensate, titanium hydroxide, and a titanium hydroxide low-condensate on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet 1 to 400 parts by mass of an organic phosphoric acid compound (B) with respect to 100 parts by mass of a solid content of a titanium-containing aqueous liquid (A) obtained by mixing a seed titanium compound with hydrogen peroxide water, an inorganic phosphoric acid compound By applying and drying a surface treatment composition (X) containing 50 to 150 parts by mass of (C) (excluding a surface treatment composition containing a vanadic acid compound, a zirconium fluoride compound and a zirconium carbonate compound) The formed film has a surface-treated film having a thickness of 0.01 to 1.0 μm, and an upper layer thereof has a high molecular weight epoxy group-containing resin (D Applying a coating composition (Y) containing, high corrosion resistance surface treated steel sheet, wherein a film thickness formed by drying has a layer film of 0.3 to 2.0 .mu.m.

[2] In the surface-treated steel sheet according to [1], the coating composition (Y) further includes a polyethylene lubricant (e1) and a polytetrafluoroethylene lubricant (e2) (e1) / (e2) = A highly corrosion-resistant surface-treated steel sheet comprising a composite lubricant (E) contained in a ratio (mass ratio) of 5/5 to 1/9.
[3] In the surface-treated steel sheet according to the above [2], the coating composition (Y) is 10 to 30 parts by mass of the composite lubricant (E) in a solid content ratio of 100 parts by mass of the resin composition. A highly corrosion-resistant surface-treated steel sheet characterized by containing.
[4] The surface-treated steel sheet according to [2] or [3], wherein the polyethylene lubricant (e1) in the composite lubricant (E) has a melting point of 100 to 130 ° C. steel sheet.

[5] In the surface-treated steel sheet according to any one of [2] to [4], the average particle size of the polytetrafluoroethylene-based lubricant (e2) in the composite lubricant (E) is 1 to 7 μm. High corrosion resistance surface-treated steel sheet.
[6] In the surface-treated steel sheet according to any one of [1] to [5], the surface treatment composition (X) further contains a water-soluble organic resin and / or a water-dispersible organic resin (F) in a titanium-containing aqueous solution. A highly corrosion-resistant surface-treated steel sheet comprising 2000 parts by mass or less in a solid content ratio with respect to 100 parts by mass of the solid content of the liquid (A).
[7] In the surface-treated steel sheet according to any one of [1] to [6], the coating composition (Y) further contains a non-chromium-based anticorrosive additive (G) in a solid content of 100 parts by mass. A highly corrosion-resistant surface-treated steel sheet, which is contained in an amount of 0.1 to 50 parts by mass with respect to the solid content.

[8] In the surface-treated steel sheet according to [7], the coating composition (Y) contains at least one selected from the following (g1) to (g5) as the non-chromium-based anticorrosive additive (G). A highly corrosion-resistant surface-treated steel sheet characterized by:
(G1) silicon oxide (g2) calcium compound (g3) phosphate compound (g4) molybdate compound (g5) one or more organic compounds selected from triazoles, thiols, thiadiazoles, thiazoles, thiurams [9] In the surface-treated steel sheet according to any one of [1] to [8], the coating composition (Y) further contains a curing agent (H) having a group that crosslinks with a hydroxyl group, a high molecular weight epoxy group-containing resin ( A highly corrosion-resistant surface-treated steel sheet, which is contained in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the solid content of D).

[10] The surface-treated steel sheet according to [9], wherein the curing agent (H) having a group that crosslinks with a hydroxyl group is an amino resin (I) having an average of one or more imino groups in one molecule. High corrosion resistance surface-treated steel sheet.
[11] The surface-treated steel sheet according to [9], wherein the curing agent (H) having a group that crosslinks with a hydroxyl group is a polyisocyanate compound (J) having an average of 4 or more isocyanate groups in one molecule. High corrosion resistance surface treated steel sheet.
[12] The surface-treated steel sheet according to [11], wherein the polyisocyanate compound (J) has at least a part of isocyanate groups blocked with a blocking agent.
[13] In the surface-treated steel sheet according to any one of [1] to [12] above, the high molecular weight epoxy group-containing resin (D) in the coating composition (Y) has a part or all of the compounds having active hydrogen. A highly corrosion-resistant surface-treated steel sheet, which is a modified epoxy group-containing resin modified with an active hydrogen-containing compound (K) comprising a hydrazine derivative (L).

  The surface-treated steel sheet of the present invention has a very excellent flat plate and corrosion resistance after processing, and also has excellent adhesion and bondability, and weldability and paintability, despite the fact that it does not contain hexavalent chromium in the film. Also excellent. For this reason, the surface-treated steel sheet of the present invention is particularly useful for automobile applications.

The details of the present invention and the reasons for limitation will be described below.
Examples of the galvanized steel sheet used as the base of the surface-treated steel sheet of the present invention include a galvanized steel sheet, a Zn—Ni alloy plated steel sheet, a Zn—Fe alloy plated steel sheet (electroplated steel sheet, galvannealed steel sheet), Zn -Cr alloy plated steel sheet, Zn-Mn alloy plated steel sheet, Zn-Co alloy plated steel sheet, Zn-Co-Cr alloy plated steel sheet, Zn-Cr-Ni alloy plated steel sheet, Zn-Cr-Fe alloy plated steel sheet, Zn-Al Alloy-plated steel sheet (for example, Zn-5% Al alloy-plated steel sheet, Zn-55% Al alloy-plated steel sheet), Zn-Mg alloy-plated steel sheet, Zn-Al-Mg alloy-plated steel sheet (for example, Zn-6% Al-3) % Mg alloy-plated steel sheet, Zn-11% Al-3% Mg alloy-plated steel sheet), and metal oxides and polymers in the plating film of these plated steel sheets Etc. can be used as dispersed zinc composite-plated steel sheet (for example, Zn-SiO ₂ dispersion plating steel plate).

In addition, among the above-described plating, a multi-layer plated steel sheet in which two or more layers of the same type or different types are plated can be used.
Moreover, as an aluminum system plated steel plate used as the base of the surface treatment steel plate of this invention, an aluminum plating steel plate, an Al-Si alloy plating steel plate, etc. can be used.
Moreover, as a plated steel plate, the steel plate surface may be plated in advance with thinning such as Ni, and the above-described various plating may be performed thereon.
As a plating method, any feasible method among an electrolytic method (electrolysis in an aqueous solution or electrolysis in a nonaqueous solvent), a melting method, and a gas phase method can be employed.
Furthermore, in order to prevent blackening of the plating, about 1 to 2000 ppm of one or more trace elements of Ni, Co, and Fe are deposited in the plating film, or one of Ni, Co, and Fe is deposited on the surface of the plating film. You may make it precipitate these elements by performing the surface adjustment process by the alkaline aqueous solution or acidic aqueous solution containing the above.

Next, the surface treatment film formed as the first layer film and the surface treatment composition for forming this film on the surface of the zinc-based plated steel sheet or the aluminum-based plated steel sheet will be described.
In the surface-treated steel sheet of the present invention, the surface-treated film formed on the surface of the zinc-based plated steel sheet or the aluminum-based plated steel sheet is composed of a specific titanium-containing aqueous liquid (A), an organic phosphate compound (B), and an inorganic phosphate compound. The surface treatment composition (X) containing (C) as an essential component is applied and dried. This surface treatment film does not contain chromium (except for chromium as an inevitable impurity).

  This surface treatment film is dense and excellent in adhesion to the base metal. The reason for this is not necessarily clear, but in the process in which a treatment solution in which an appropriate amount of an organic phosphate compound and an inorganic phosphate compound are added to a specific titanium-based aqueous solution is applied to the plating surface and dried, The plating surface is etched, resulting in the formation of a composite salt of the metal ions eluted and the metal ions and phosphoric acid contained in the treatment solution, and the deposition of a dense titanium oxide-based film component. This is considered to be because a film having a high corrosion inhibition ability is formed.

The titanium-containing aqueous liquid (A) contains at least one titanium compound selected from hydrolyzable titanium compounds, hydrolyzable titanium compound low condensates, titanium hydroxide, and titanium hydroxide low condensates. It is an aqueous liquid containing titanium obtained by mixing with hydrogen oxide water.
The hydrolyzable titanium compound is a titanium compound having a hydrolyzable group directly bonded to titanium, and generates titanium hydroxide by reacting with water such as water or water vapor. The hydrolyzable titanium compound may be one in which all of the groups bonded to titanium are hydrolyzable groups, or a part of the groups bonded to titanium may be hydrolyzable groups.
The hydrolyzable group is not particularly limited as long as it generates titanium hydroxide by reacting with moisture as described above. For example, a lower alkoxyl group or a group that forms a salt with titanium (for example, Halogen atoms such as chlorine, hydrogen atoms, sulfate ions, etc.).

The hydrolyzable titanium compound containing a lower alkoxyl group as the hydrolyzable group is particularly represented by the general formula Ti (OR) ₄ (wherein R represents the same or different alkyl groups having 1 to 5 carbon atoms). Tetraalkoxy titanium is preferred. Examples of the alkyl group having 1 to 5 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, and a tert-butyl group. Can be mentioned.
Typical examples of the hydrolyzable titanium compound having a group capable of forming a salt with titanium as a hydrolyzable group include titanium chloride and titanium sulfate.

Moreover, the low condensate of a hydrolysable titanium compound is a low condensate of the above-mentioned hydrolysable titanium compounds. The low condensate may be one in which all of the groups bonded to titanium are hydrolyzable groups, or a part of the groups bonded to titanium may be hydrolyzable.
For hydrolyzable titanium compounds whose hydrolyzable group forms a salt with titanium (for example, titanium chloride, titanium sulfate, etc.), an aqueous solution of the hydrolyzable titanium compound and an alkaline solution such as ammonia or caustic soda are used. Orthotitanic acid (titanium hydroxide gel) obtained by the reaction can also be used as a low condensate.

As the low condensate of the hydrolyzable titanium compound and the low condensate of titanium hydroxide, a compound having a condensation degree of 2 to 30 can be used, and a compound having a condensation degree of 2 to 10 is particularly preferable. When the condensation degree exceeds 30, a white precipitate is formed when mixed with hydrogen peroxide, and a stable titanium-containing aqueous liquid cannot be obtained.
The hydrolyzable titanium compounds listed above, low-condensates of hydrolyzable titanium compounds, titanium hydroxide, and low-condensates of titanium hydroxide can be used alone or in combination of two or more thereof. Tetraalkoxy titanium which is a hydrolyzable titanium compound represented by the formula is particularly preferable.

As the titanium-containing aqueous liquid (A), any conventionally known liquid can be used without particular limitation as long as it is an aqueous liquid containing titanium obtained by mixing the above-described titanium compound and hydrogen peroxide solution. Specifically, the following can be mentioned.
(I) A titanyl ion hydrogen peroxide complex or an aqueous solution of titanic acid (peroxotitanium hydrate) obtained by adding hydrogen peroxide to a hydrous titanium oxide gel or sol (JP-A 63-35419, JP 1-2224220 gazette).

(Ii) A liquid for forming a titania film obtained by synthesizing a titanium hydroxide gel produced from an aqueous solution of titanium chloride or titanium sulfate and a basic solution with a hydrogen peroxide solution (Japanese Patent Laid-Open No. 9-71418, (See Kaihei 10-67516).
When obtaining this titania film-forming liquid, titanium hydroxide gel called orthotitanic acid is precipitated by reacting an aqueous solution of titanium chloride or titanium sulfate having a salt-forming group with titanium and an alkaline solution such as ammonia or caustic soda. Let Next, the titanium hydroxide gel is separated by decantation with water, washed thoroughly with water, further added with hydrogen peroxide water, and excess hydrogen peroxide is decomposed and removed, whereby a yellow transparent viscous liquid can be obtained.

The precipitated orthotitanic acid is in a gel state polymerized by polymerization of OH or hydrogen bonds, and cannot be used as an aqueous liquid containing titanium as it is. When hydrogen peroxide solution is added to this gel, a part of OH is in a peroxidized state, dissolved as a peroxotitanate ion or in a kind of sol state in which the polymer chain is divided into low molecules, and excess hydrogen peroxide Is decomposed into water and oxygen, and can be used as an aqueous liquid containing titanium for forming an inorganic film.
Since this sol contains only oxygen and hydrogen atoms in addition to titanium atoms, when it is changed to titanium oxide by drying or firing, only water and oxygen are generated, so carbon components necessary for thermal decomposition such as sol-gel method and sulfate Further, it is not necessary to remove the halogen component, and a titanium oxide film having a relatively high density can be formed even at a low temperature.

(Iii) Hydrogen peroxide is added to an aqueous solution of an inorganic titanium compound such as titanium chloride or titanium sulfate to form peroxotitanium hydrate, and then the resulting solution obtained by adding a basic substance is allowed to stand or be heated. A titanium oxide forming solution obtained by forming a precipitate of a titanium hydrate polymer, and then removing hydrogen and other dissolved components derived from at least a titanium-containing raw material solution (Japanese Patent Application Laid-Open 2000-247638, JP-A-2000-247639).

The titanium-containing aqueous liquid (A) using a hydrolyzable titanium compound and / or a low condensate thereof as a titanium compound (hereinafter referred to as “hydrolyzable titanium compound a” for convenience of explanation) contains hydrolyzable titanium compound a. It can be obtained by reacting with hydrogen oxide water at a reaction temperature of 1 to 70 ° C. for about 10 minutes to 20 hours.
In the titanium-containing aqueous liquid (A) using the hydrolyzable titanium compound a, the hydrolyzable titanium compound a is hydrolyzed with water by reacting the hydrolyzable titanium compound a with hydrogen peroxide. A product obtained by producing a hydroxyl group-containing titanium compound and then coordinating hydrogen peroxide to this hydroxyl group-containing titanium compound, and this hydrolysis reaction and coordination by hydrogen peroxide occur simultaneously. It produces a chelate solution that is extremely stable at room temperature and can withstand long-term storage. The titanium hydroxide gel used in the conventional manufacturing method is partially three-dimensionalized by Ti—O—Ti bonds, and the titanium-containing aqueous liquid (A) obtained by reacting this gel with hydrogen peroxide is composition and stable. Sex is essentially different.

  Further, when the titanium-containing aqueous liquid (A) using the hydrolyzable titanium compound a is heated or autoclaved at 80 ° C. or higher, a titanium oxide dispersion liquid containing ultrafine particles of crystallized titanium oxide is obtained. When the heat treatment or autoclave treatment is less than 80 ° C., crystallization of titanium oxide does not proceed sufficiently. The titanium oxide dispersion thus produced has an average particle diameter of titanium oxide ultrafine particles of 10 nm or less, preferably about 1 to 6 nm. When the average particle diameter of the titanium oxide ultrafine particles is larger than 10 nm, the film forming property is deteriorated (when the film is dried after coating to form a film, cracking occurs at a film thickness of 1 μm or more), which is not preferable. The appearance of this titanium oxide dispersion is translucent. Such a titanium oxide dispersion can also be used as the titanium-containing aqueous liquid (A).

By applying and drying the surface treatment composition (X ₀ ) containing the titanium-containing aqueous liquid (A) using the hydrolyzable titanium compound a on the surface of the plated steel sheet (for example, heat drying at a low temperature), the surface treatment composition (X ₀ ) A dense titanium oxide-containing film (surface treatment film) having excellent adhesion can be formed.
The heating temperature after applying the surface treatment composition (X ₀ ) is, for example, preferably 200 ° C. or lower, particularly preferably 150 ° C. or lower. ) Of titanium oxide containing film can be formed.
Moreover, when the titanium oxide dispersion obtained through the heat treatment or autoclave treatment as described above at 80 ° C. or more is used as the titanium-containing aqueous liquid (A), only the surface treatment composition (X ₀ ) is applied. Since a crystalline titanium oxide-containing film can be formed, it is useful as a coating material for materials that cannot be heat-treated.

Further, as the titanium-containing aqueous liquid (A), a titanium-containing aqueous liquid (A1) obtained by reacting the hydrolyzable titanium compound a with hydrogen peroxide in the presence of a titanium oxide sol can also be used. .
The titanium oxide sol is a sol in which amorphous titania fine particles and / or anatase titania fine particles are dispersed in water (for example, an aqueous organic solvent such as an alcohol or alcohol ether may be added if necessary). As this titanium oxide sol, conventionally known ones can be used. For example, (i) a titanium oxide aggregate obtained by hydrolyzing a titanium-containing solution such as titanium sulfate or titanyl sulfate, (ii) titanium alkoxide, etc. Titanium oxide aggregates obtained by hydrolyzing organic titanium compounds of (ii), titanium oxide aggregates obtained by hydrolyzing or neutralizing titanium halide solutions such as titanium tetrachloride, etc. An amorphous titania sol dispersed in water, or a sol in which the titanium oxide aggregates are calcined to form anatase-type titanium fine particles and this is dispersed in water can be used.

In the firing of the amorphous titania, the amorphous titania can be converted into anatase titania by firing at a temperature of at least the crystallization temperature of anatase, for example, a temperature of 400 ° C. to 500 ° C. or more. Examples of the aqueous sol of titanium oxide include, for example, TKS-201 (trade name, manufactured by Teika, anatase crystal form, average particle diameter 6 nm), TA-15 (trade name, manufactured by Nissan Chemical Co., anatase crystal form). STS-11 (trade name, manufactured by Ishihara Sangyo Co., Ltd., anatase type crystal form) and the like.
In the titanium-containing aqueous liquid (A1), the mass ratio x / y between the titanium oxide sol x and the titanium hydrogen peroxide reactant y (reaction product of the hydrolyzable titanium compound a and hydrogen peroxide solution) is 1 / A range of 99 to 99/1, preferably about 10/90 to 90/10 is suitable. If the mass ratio x / y is less than 1/99, the effect of adding the titanium oxide sol cannot be sufficiently obtained in terms of stability, photoreactivity, etc. Absent.

The titanium-containing aqueous liquid (A1) can be obtained by reacting the hydrolyzable titanium compound a with hydrogen peroxide at a reaction temperature of 1 to 70 ° C. for about 10 minutes to 20 hours in the presence of a titanium oxide sol.
The production form and characteristics of the titanium-containing aqueous liquid (A1) are the same as those of the titanium-containing aqueous liquid (A) using the hydrolyzable titanium compound a described above, but in particular, by using a titanium oxide sol. , It is possible to suppress a partial condensation reaction during the synthesis to increase the viscosity. The reason is considered to be that the condensation reaction product is adsorbed on the surface of the titanium oxide sol, and polymerization in a solution state is suppressed.

  Further, when the titanium-containing aqueous liquid (A1) is subjected to a heat treatment or autoclave treatment at 80 ° C. or higher, a titanium oxide dispersion containing ultrafine particles of crystallized titanium oxide is obtained. The titanium-containing aqueous liquid (A) using the hydrolyzable titanium compound a described above also describes the temperature conditions for obtaining this titanium oxide dispersion, the particle diameter of the crystallized titanium oxide ultrafine particles, the appearance of the dispersion, etc. It is the same. Such a titanium oxide dispersion can also be used as the titanium-containing aqueous liquid (A1).

Like the titanium-containing aqueous liquid (A) using the hydrolyzable titanium compound a described above, the surface treatment composition (X ₀ ) containing the titanium-containing aqueous liquid (A1) is applied to the surface of the plated steel sheet and dried ( For example, by performing heat drying at a low temperature, a dense titanium oxide-containing film (surface treatment film) having excellent adhesion can be formed.
The heating temperature after applying the surface treatment composition (X ₀ ) is, for example, preferably 200 ° C. or less, particularly preferably 150 ° C. or less. By heating and drying at such a temperature, anatase-type titanium oxide containing some hydroxyl groups. A contained film can be formed.
As described above, of the titanium-containing aqueous liquid (A), the titanium-containing aqueous liquid (A) and the titanium-containing aqueous liquid (A1) using the hydrolyzable titanium compound a are excellent in storage stability, corrosion resistance, and the like. It is particularly preferable to use these in the present invention.

  The compounding ratio of hydrogen peroxide water to at least one titanium compound selected from hydrolyzable titanium compounds, hydrolyzable titanium compound low condensates, titanium hydroxide, titanium hydroxide low condensates is titanium compounds It is preferably 0.1 to 100 parts by mass, preferably 1 to 20 parts by mass in terms of hydrogen peroxide with respect to 10 parts by mass. If the blending ratio of the hydrogen peroxide solution is less than 0.1 parts by mass in terms of hydrogen peroxide, chelate formation is not sufficient and white turbid precipitation occurs. On the other hand, if it exceeds 100 parts by mass, unreacted hydrogen peroxide tends to remain, and dangerous active oxygen is released during storage, which is not preferable.

The hydrogen peroxide concentration of the hydrogen peroxide solution is not particularly limited, but it is preferably about 3 to 30% by mass from the viewpoint of ease of handling and the solid content of the product liquid related to coating workability.
Other sols and pigments can be added and dispersed in the titanium-containing aqueous liquid (A) as necessary. Examples of the additive include commercially available titanium oxide sol, titanium oxide powder, mica, talc, silica, barita, clay, and the like, and one or more of these can be added.
The content of the titanium-containing aqueous liquid (A) in the surface treatment composition (X) is 1 to 100 g / L, preferably 5 to 50 g / L in terms of solid content. It is preferable from the point.

  Examples of the organic phosphate compound (B) include 1-hydroxymethane-1,1-diphosphonic acid, 1-hydroxyethane-1,1-diphosphonic acid, 1-hydroxypropane-1,1-diphosphonic acid, and the like. Suitable examples include hydroxyl group-containing organic phosphorous acid; carboxyl group-containing organic phosphorous acid such as 2-hydroxyphosphonoacetic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, and salts thereof. These 1 type (s) or 2 or more types can be used.

The organic phosphoric acid compound (B) has a large effect of improving the storage stability of the titanium-containing aqueous liquid (A). Among them, 1-hydroxyethane-1,1-diphosphonic acid has a particularly large effect. It is particularly preferred to use this.
The compounding amount of the organic phosphoric acid compound (B) is 1 to 400 parts by mass, particularly 20 to 300 parts by mass in terms of the solid content with respect to 100 mass parts of the solid content of the titanium-containing aqueous liquid (A). This is preferable from the viewpoint of water resistance adhesion. If the amount of the organic phosphoric acid compound (B) is less than 1 part by mass with respect to 100 parts by mass of the solid content of the titanium-containing aqueous liquid (A), the corrosion resistance is inferior. However, it is not preferable because water adhesion and corrosion resistance are inferior.

The inorganic phosphate compound (C) improves adhesion by etching (reacting) the surface of the plating film, and forms a composite film of the eluted metal ions and phosphoric acid, titanium compounds, etc. By doing so, a dense barrier film is formed.
Examples of the inorganic phosphoric acid compound (C) include phosphorous acid, strong phosphoric acid, triphosphoric acid, hypophosphorous acid, hypophosphoric acid, trimetaphosphoric acid, diphosphorous acid, diphosphoric acid, pyrophosphorous acid, List monophosphoric acids such as pyrophosphoric acid, metaphosphorous acid, metaphosphoric acid, orthophosphoric acid, derivatives and salts of monophosphoric acid, condensed phosphoric acids such as tripolyphosphoric acid, tetraphosphoric acid, hexaphosphoric acid, derivatives and salts of condensed phosphoric acids, etc. 1 type, or 2 or more types of these can be used. Of these, phosphoric acids are more preferable than phosphoric acid derivatives and salts from the viewpoint of reactivity with plating. It is preferable to use an inorganic phosphate compound that is soluble in water. In particular, orthophosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, tetraphosphoric acid, metaphosphoric acid, hexametaphosphoric acid and the like are preferable from the viewpoint of storage stability, corrosion resistance, and adhesiveness of the treatment liquid.

  The compounding amount of the inorganic phosphoric acid compound (C) is 50 to 150 parts by mass, particularly 70 to 120 parts by mass in terms of the solid content with respect to 100 mass parts of the solid content of the titanium-containing aqueous liquid (A). It is preferable from the viewpoint of adhesive bondability. If the blending amount of the inorganic phosphate compound (C) is less than 50 parts by mass with respect to 100 parts by mass of the solid content of the titanium-containing aqueous liquid (A), the adhesive bondability is inferior. Is lowered, the adhesiveness is inferior, and the water adhesion and corrosion resistance are inferior.

The surface treatment composition (X) can further contain a water-soluble organic resin and / or a water-dispersible organic resin (F), thereby improving paintability.
This water-soluble organic resin and / or water-dispersible organic resin (F) is an organic resin that can be dissolved or dispersed in water, and a conventionally known method for water-solubilizing or dispersing an organic resin in water is known. The method can be applied. Specifically, the organic resin contains a functional group (for example, a hydroxyl group, a polyoxyalkylene group, a carboxyl group, an amino (imino) group, a sulfide group, a phosphine group, etc.) that can be water-soluble or water-dispersed independently. And, if necessary, part or all of these functional groups may be converted to acidic compounds (such as carboxyl group-containing resins) with amine compounds such as ethanolamine and triethylamine; ammonia water; lithium hydroxide, sodium hydroxide, water Neutralized with alkali metal hydroxides such as potassium oxide, and fatty acids such as acetic acid and lactic acid for basic resins (amino group-containing resins); those neutralized with mineral acids such as phosphoric acid Can be used.

Examples of water-soluble or water-dispersible organic resins include epoxy resins, phenol resins, acrylic resins, urethane resins, olefin-carboxylic acid resins, nylon resins, resins having a polyoxyalkylene chain, and polyvinyl alcohol. , Polyglycerin, carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose and the like. The said organic resin can use 1 type (s) or 2 or more types.
Among these, in particular, the storage stability of the surface treatment composition (X) is obtained by using at least one organic resin selected from water-soluble or water-dispersible acrylic resins, urethane resins and epoxy resins. In view of the above, it is particularly preferable to use a water-soluble or water-dispersible acrylic resin as a main component from the viewpoint of the balance between the storage stability of the surface treatment composition (X) and the coating film performance.

A water-soluble or water-dispersible acrylic resin is synthesized by a conventionally known method, for example, an emulsion polymerization method, a suspension polymerization method, or a polymer having a hydrophilic group by solution polymerization. Or the like.
The polymer having a hydrophilic group includes, for example, an unsaturated monomer having a hydrophilic group such as a carboxyl group, an amino group, a hydroxyl group, and a polyoxyalkylene group, and, if necessary, other unsaturated monomers. It can be obtained by polymerizing the monomer.
The water-soluble or water-dispersible acrylic resin is preferably obtained by copolymerizing styrene from the viewpoint of corrosion resistance and the like. The amount of styrene in the total unsaturated monomer is 10 to 60% by mass, particularly 15 to 50% by mass. It is preferable that Moreover, it is preferable from points, such as toughness of the film obtained, that Tg (glass transition point) of the acrylic resin obtained by copolymerization is 30-80 degreeC, especially 40-70 degreeC.

Examples of the carboxyl group-containing unsaturated monomer include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, crotonic acid, and itaconic acid.
Examples of the nitrogen-containing unsaturated monomer such as the amino group-containing unsaturated monomer include N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, Nt- Nitrogen-containing alkyl (meth) acrylates such as butylaminoethyl (meth) acrylate; acrylamide, methacrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl Polymerization of (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylamide, etc. Amides; 2-vinylpyridine, - vinyl-2-pyrrolidone, aromatic nitrogen-containing monomers such as 4-vinylpyridine; and allylamine and the like.

  Examples of the hydroxyl group-containing unsaturated monomer include 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2,3-dihydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, polyethylene glycol mono Monoesterified product of polyhydric alcohol such as (meth) acrylate and polypropylene glycol mono (meth) acrylate and acrylic acid or methacrylic acid; ε-caprolactone is opened to monoesterified product of polyhydric alcohol and acrylic acid or methacrylic acid. Examples include a ring-polymerized compound.

Other unsaturated monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, 1 carbon number such as tert-butyl (meth) acrylate, 2-ethylhexyl acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, octadecyl (meth) acrylate, isostearyl (meth) acrylate -24 alkyl (meth) acrylates; vinyl acetate and the like.
The unsaturated monomer mentioned above can use 1 type (s) or 2 or more types. In the description of the present application, “(meth) acrylate” means “acrylate or methacrylate”.

  Examples of the urethane resin include a chain extender that is a low molecular weight compound having two or more active hydrogens such as a diol and a diamine, if necessary, and a polyurethane comprising a polyol and a diisocyanate such as a polyester polyol and a polyether polyol. Those which are chain-extended in the presence and stably dispersed or dissolved in water can be suitably used, and conventionally known ones can be widely used (for example, Japanese Patent Publication No. 42-24192, Japanese Patent Publication No. 42-24194, (See JP-B-42-5118, JP-B-49-986, JP-B-49-33104, JP-B-50-15027, JP-B-53-29175).

As a method for stably dispersing or dissolving the polyurethane resin in water, for example, the following method can be used.
(1) A method of imparting hydrophilicity by introducing an ionic group such as a hydroxyl group, an amino group or a carboxyl group into the side chain or terminal of a polyurethane polymer, and dispersing or dissolving in water by self-emulsification.
(2) A polyurethane polymer whose reaction has been completed or a polyurethane polymer whose terminal isocyanate group is blocked with a blocking agent such as oxime, alcohol, phenol, mercaptan, amine or sodium bisulfite is forcibly submerged in water using an emulsifier and mechanical shearing force. How to disperse. Further, a method in which a urethane polymer having a terminal isocyanate group is mixed with water, an emulsifier and a chain extender, and dispersion and high molecular weight are simultaneously performed using mechanical shearing force.
(3) A method in which a water-soluble polyol such as polyethylene glycol is used as a polyol as a main polyurethane material and is dispersed or dissolved in water as a water-soluble polyurethane.
In addition, as the polyurethane resin, those obtained by different methods among the above-described dispersion or dissolution methods can be mixed and used.

Examples of the diisocyanate that can be used for the synthesis of the polyurethane resin include aromatic, alicyclic or aliphatic diisocyanates. Specifically, hexamethylene diisocyanate, tetramethylene diisocyanate, 3,3′-dimethoxy-4, 4'-biphenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, 1,3- (diisocyanatomethyl) cyclohexanone, 1,4- (diisocyanatomethyl) cyclohexanone, 4,4'-diisocyanato Cyclohexanone, 4,4'-methylenebis (cyclohexyl isocyanate), isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-phenylene diisocyanate, diphenylmethane Isocyanate, m- phenylene diisocyanate, 2,4-naphthalene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 4,4'-biphenylene diisocyanate and the like. Among these, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate are particularly preferable.
Examples of commercially available polyurethane resins include Hydran HW-330, HW-340, HW-350 (both trade names, manufactured by Dainippon Ink and Chemicals), Superflex 100, 150, E-2500, F-3438D (all are trade names, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

  As the epoxy resin, a cationic epoxy resin obtained by adding an amine to an epoxy resin; a modified epoxy resin such as an acrylic modification or a urethane modification can be suitably used. Examples of cationic epoxy resins include adducts of epoxy compounds with primary mono- or polyamines, secondary mono- or polyamines, and primary and secondary mixed polyamines (see, for example, US Pat. No. 3,984,299). An adduct of an epoxy compound with a secondary mono- or polyamine having a ketiminated primary amino group (see, for example, US Pat. No. 4,017,438); having an epoxy compound and a primary amino group ketiminated Examples include etherification reaction products with hydroxyl compounds (see, for example, JP-A-59-43013).

The epoxy resin preferably has a number average molecular weight of 400 to 4000, particularly 800 to 2000, and an epoxy equivalent of 190 to 2000, particularly 400 to 1000. Such an epoxy resin can be obtained, for example, by a reaction between a polyphenol compound and epichlorohydrin. Examples of the polyphenol compound include bis (4-hydroxyphenyl) -2,2-propane and 4,4-dihydroxybenzophenone. Bis (4-hydroxyphenyl) -1,1-ethane, bis (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-tert-butylphenyl) -2,2-propane, bis (2 -Hydroxynaphthyl) methane, 1,5-dihydroxynaphthalene, bis (2,4-dihydroxyphenyl) methane, tetra (4-hydroxyphenyl) -1,1,2,2-ethane, 4,4-dihydroxydiphenylsulfone, Phenol novolak, cresol novolak, etc. That.
The blending amount of the water-soluble organic resin and / or the water-dispersible organic resin (F) is 2000 parts by mass or less, particularly 5 to 1500 in terms of the solid content with respect to 100 mass parts of the solid content of the titanium-containing aqueous liquid (A). It is preferable to set it as a mass part from points, such as corrosion resistance after alkali degreasing. When the blending amount of the water-soluble organic resin and / or water-dispersible organic resin (F) exceeds 2000 parts by mass with respect to 100 parts by mass of the solid content of the titanium-containing aqueous liquid (A), the corrosion resistance after alkali degreasing is reduced. Since it is inferior, it is not preferable.

A silane coupling agent can be further added to the surface treatment composition (X) as necessary. Examples of the silane coupling agent include N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N- β (N-vinylbenzylaminoethyl) γ-aminopropyltrimethoxysilane hydrochloride, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopyrrolotrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, methyltrimethoxy Silane, vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane, hexamethyldisilazane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, octadecyldimethyl [3- (trimethoxysilane Yl) propyl] ammonium chloride, trimethylchlorosilane, and the like, and one or more of these may be used.
The compounding amount of the silane coupling agent is 1 to 400 parts by weight, particularly 10 to 400 parts by weight, based on 100 parts by weight of the solid content of the titanium-containing aqueous liquid (A). From the point of view, it is preferable.

If necessary, organic fine particles and / or inorganic fine particles can be further added to the surface treatment composition (X). By adding such fine particles, the transparency of the coating film is lowered, and nitrite (interference color) that tends to occur in the thin film can be suppressed. The fine particles preferably have an average particle size of 3 to 1000 nm, particularly 3 to 500 nm, from the viewpoint of sedimentation stability and corrosion resistance of the particles.
Examples of the organic fine particles include resin fine particles such as acrylic, polyurethane, nylon, and polyethylene glycol. Examples of the inorganic fine particles include silica, titanium dioxide, barium sulfate, and calcium carbonate. From the viewpoint of cost, silica, titanium dioxide, barium sulfate and the like are particularly preferable.
The blending amount of the organic fine particles and / or inorganic fine particles is preferably 1 to 30% by mass, particularly 1 to 20% by mass in the solid content of the surface treatment composition (X) from the viewpoint of corrosion resistance and the like.

In the surface treatment composition (X), if necessary, an etching agent such as hydrofluoric acid, a heavy metal compound other than the components specified by the present invention, an aqueous organic polymer compound, a thickener, a surfactant, Rust preventives (tannic acid, phytic acid, benzotriazole, etc.), colored pigments, extender pigments, silica, rust preventive pigments and the like can be added.
The surface treatment composition (X) is usually diluted with water and used. If necessary, for example, a hydrophilic solvent such as methanol, ethanol, isopropyl alcohol, an ethylene glycol solvent, or a propylene glycol solvent. It may be diluted with.
Since the surface treatment composition (X) becomes a stable liquid in a neutral or acidic region, pH 1 to 7, particularly 1 to 5 is particularly preferable.
The film thickness of the surface treatment film formed by the surface treatment composition (X) is 0.01 to 1.0 μm, preferably 0.05 from the viewpoints of economy and film performance, particularly corrosion resistance, adhesion and weldability. ˜0.7 μm. If the film thickness is less than 0.01 μm, sufficient corrosion resistance cannot be obtained. On the other hand, if it exceeds 1.0 μm, the weldability is inferior, and the post-processing corrosion resistance and electrodeposition coating properties also deteriorate.

Next, in the surface-treated steel sheet of the present invention, the upper layer film formed on the surface-treated film described above will be described.
This upper layer film is formed by applying and drying a coating composition (Y) containing a high molecular weight epoxy group-containing resin (D) having a number average molecular weight of 6000 to 20000, preferably using this as a main component resin. The film thickness is 0.3 to 2.0 μm. This upper layer film also does not contain chromium (except for chromium as an inevitable impurity). By forming such a specific resin film on the upper layer of the specific surface treatment film (lower film), particularly high corrosion resistance of the processed part can be obtained by the combined action of both films.

In the present invention, the reason why the epoxy group-containing resin (D) is used for the upper layer film is that the aspects such as reactivity, easiness of reaction, and corrosion resistance are superior to other resins. Examples of the epoxy group-containing resin (D) include an epoxy resin, a modified epoxy resin, an acrylic copolymer resin copolymerized with an epoxy group-containing monomer, a polybutadiene resin having an epoxy group, a polyurethane resin having an epoxy group, and Examples include adducts or condensates of these resins. One of these epoxy group-containing resins can be used alone or in admixture of two or more.
Of these epoxy group-containing resins (D), epoxy resins and modified epoxy resins are particularly preferred from the viewpoints of adhesion to the plating surface and corrosion resistance. Of these, thermosetting epoxy resins and modified epoxy resins that have excellent barrier properties against corrosive factors such as oxygen are optimal, and in particular, the coating amount is low to obtain high spot weldability. This is particularly advantageous.

As the epoxy group-containing resin (D), a high molecular weight epoxy group-containing resin having a number average molecular weight of 6000 to 20000, preferably 7000 to 12000 is used. Among these, bisphenol type epoxy resins are preferable. Generally used bisphenol type epoxy resins have a number average molecular weight of 5500 or less, but if the number average molecular weight is less than 6000, the processability of the resulting film is not sufficient, especially for automotive press dies. The film damage when subjected to severe processing by a certain wrinkle presser bead is large, and the corrosion resistance of the processed part is inferior. On the other hand, when the number average molecular weight exceeds 20000, it is very difficult to produce an epoxy resin, and it becomes difficult to obtain a product having a stable quality due to gelation or the like.
As the bisphenol type epoxy resin, for example, a resin obtained by condensing epichlorohydrin and bisphenol to a high molecular weight in the presence of a catalyst such as an alkali catalyst, if necessary, epichlorohydrin and bisphenol, if necessary, an alkali catalyst Any of the resins obtained by condensation in the presence of a catalyst to form a low molecular weight epoxy resin and a polyaddition reaction of this low molecular weight epoxy resin and bisphenol may be used. The latter method is preferred for obtaining the above.

  Examples of the bisphenol include bis (4-hydroxyphenyl) methane [bisphenol F], 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane [bisphenol A], 2,2-bis (4-hydroxyphenyl) butane [bisphenol B], bis (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-tert-butyl-phenyl) -2,2-propane, Examples thereof include p- (4-hydroxyphenyl) phenol, oxybis (4-hydroxyphenyl), sulfonylbis (4-hydroxyphenyl), 4,4′-dihydroxybenzophenone, bis (2-hydroxynaphthyl) methane, and the like. Bis (4-hydroxyphenyl) methane Bisphenol F] and 2,2-bis (4-hydroxyphenyl) propane [bisphenol A] is preferable. The said bisphenol can be used individually by 1 type or in mixture of 2 or more types.

As said modified | denatured epoxy resin, an acrylic modified epoxy resin, a polyester modified epoxy resin, a urethane modified epoxy resin etc. can be mentioned, for example. Also, a polyalkylene glycol-modified epoxy resin obtained by reacting polyalkylene glycol, polyisocyanate and an epoxy resin, or a modification obtained by reacting an epoxy resin with an active hydrogen-containing compound comprising a hydrazine derivative in which some or all of the compounds have active hydrogen. Epoxy resins (hydrazine derivative-modified epoxy resins) can also be used. Of these, hydrazine derivative-modified epoxy resins are particularly preferred from the standpoint of improving corrosion resistance.
The modified epoxy resin may be one in which various modifiers are reacted with the epoxy group or hydroxyl group in the epoxy resin, and includes, for example, an epoxy ester resin reacted with a dry oil fatty acid, acrylic acid or methacrylic acid, etc. Examples thereof include an epoxy acrylate resin modified with a polymerizable unsaturated monomer component and a urethane-modified epoxy resin reacted with an isocyanate compound.

As the acrylic copolymer resin copolymerized with the epoxy group-containing monomer, an unsaturated monomer having an epoxy group and a polymerizable unsaturated monomer component essentially comprising an acrylic ester or a methacrylic ester, a solution polymerization method, Examples thereof include resins synthesized by an emulsion polymerization method or a suspension polymerization method.
Examples of the polymerizable unsaturated monomer component include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-, iso- or tert-butyl (meth) acrylate, hexyl (meth) acrylate, C1-24 alkyl ester of acrylic acid or methacrylic acid such as 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate; acrylic acid, methacrylic acid, styrene, vinyltoluene, acrylamide, acrylonitrile, N- Examples thereof include methylol (meth) acrylamide, C1-4 alkyl etherified product of N-methylol (meth) acrylamide; N, N-diethylaminoethyl methacrylate and the like.
The unsaturated monomer having an epoxy group is not particularly limited as long as it has an epoxy group and a polymerizable unsaturated group, such as glycidyl methacrylate, glycidyl acrylate, and 3,4-epoxycyclohexylmethyl (meth) acrylate. .

  Modified epoxy obtained by reacting an active hydrogen-containing compound (K) composed of a hydrazine derivative (L) in which some or all of the compounds have active hydrogen, represented by the hydrazine derivative-modified epoxy resin, with a high molecular weight epoxy group-containing resin. The group-containing resin may form a film with improved adhesion and excellent corrosion resistance when the hydrazine derivative (L) having active hydrogen reacts with the epoxy group of the high molecular weight epoxy group-containing resin. it can.

Examples of the active hydrogen-containing compound (K) that reacts with the epoxy group of the high molecular weight epoxy group-containing resin include those shown below, and one or more of these compounds can be used. At least a part (preferably all) of the hydrogen-containing compound (K) needs to be a hydrazine derivative (L) having active hydrogen. That is, among these, a hydrazine derivative (L) having active hydrogen is an essential component, and an active hydrogen-containing compound other than the hydrazine derivative (L) is used as necessary.
・ Hydrazine derivatives with active hydrogen ・ Primary or secondary amine compounds with active hydrogen ・ Organic acids such as ammonia and carboxylic acids ・ Halogen halides such as hydrogen chloride ・ Alcohols and thiols ・ Having active hydrogen Quaternary chlorinating agent which is a mixture of hydrazine derivative or tertiary amine and acid

Examples of the hydrazine derivative (L) having active hydrogen include the following.
(1) Carbohydrazide, propionic acid hydrazide, salicylic acid hydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanoic acid dihydrazide, isophthalic acid dihydrazide, thiocarbohydrazide, 4,4'-oxybisbenzenesulfonylhydrazide, benzophenone hydrazone, aminopolyacrylamide Hydrazide compounds such as;
(2) pyrazole compounds such as pyrazole, 3,5-dimethylpyrazole, 3-methyl-5-pyrazolone, 3-amino-5-methylpyrazole;
(3) 1,2,4-triazole, 3-amino-1,2,4-triazole, 4-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole, 5-amino -3-mercapto-1,2,4-triazole, 2,3-dihydro-3-oxo-1,2,4-triazole, 1H-benzotriazole, 1-hydroxybenzotriazole (monohydrate), 6- Triazole compounds such as methyl-8-hydroxytriazolopyridazine, 6-phenyl-8-hydroxytriazolopyridazine, 5-hydroxy-7-methyl-1,3,8-triazaindolizine;

(4) tetrazole compounds such as 5-phenyl-1,2,3,4-tetrazole and 5-mercapto-1-phenyl-1,2,3,4-tetrazole;
(5) thiadiazole compounds such as 5-amino-2-mercapto-1,3,4-thiadiazole and 2,5-dimercapto-1,3,4-thiadiazole;
(6) Maleic hydrazide, 6-methyl-3-pyridazone, 4,5-dichloro-3-pyridazone, 4,5-dibromo-3-pyridazone, 6-methyl-4,5-dihydro-3-pyridazone, etc. Pyridazine compounds;
Of these, pyrazole compounds and triazole compounds having a 5-membered or 6-membered ring structure and having a nitrogen atom in the ring structure are particularly suitable.
These hydrazine derivatives can be used individually by 1 type or in mixture of 2 or more types.

Typical examples of the amine compound having active hydrogen that can be used as a part of the active hydrogen-containing compound (K) include the following.
(1) a primary amino group of an amine compound containing one secondary amino group and one or more primary amino groups, such as diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine, etc .; A compound modified with aldimine, ketimine, oxazoline or imidazoline by heat reaction with aldehyde or carboxylic acid at a temperature of about 100 to 230 ° C., for example;
(2) Secondary monoamines such as diethylamine, diethanolamine, di-n- or -iso-propanolamine, N-methylethanolamine, N-ethylethanolamine;
(3) a secondary amine-containing compound obtained by adding a monoalkanolamine such as monoethanolamine and a dialkyl (meth) acrylamide by a Michael addition reaction;
(4) A compound obtained by modifying a primary amino group of an alkanolamine such as monoethanolamine, neopentanolamine, 2-aminopropanol, 3-aminopropanol, 2-hydroxy-2 '(aminopropoxy) ethyl ether to ketimine;

The quaternary chlorinating agent that can be used as a part of the active hydrogen-containing compound (K) is a hydrazine derivative or a tertiary amine that does not have active hydrogen and is not reactive with an epoxy group by itself. In order to be able to react with the acid. The quaternary chlorinating agent reacts with an epoxy group in the presence of water as necessary to form a quaternary salt with the epoxy group-containing resin.
The acid used to obtain the quaternary chlorinating agent may be any of organic acids such as acetic acid and lactic acid, and inorganic acids such as hydrochloric acid. Examples of the hydrazine derivative having no active hydrogen used for obtaining a quaternary chlorinating agent include 3,6-dichloropyridazine, and examples of the tertiary amine include dimethylethanolamine, triethylamine, Examples include trimethylamine, triisopropylamine, and methyldiethanolamine.

The reaction product of the high molecular weight epoxy group-containing resin and the active hydrogen-containing compound (K) consisting of a hydrazine derivative (L) in which some or all of the compounds have active hydrogen is obtained from the high molecular weight epoxy group-containing resin and the active hydrogen-containing compound. It is obtained by reacting (K) at 10 to 300 ° C., preferably 50 to 150 ° C. for about 1 to 8 hours.
This reaction may be performed by adding an organic solvent, and the type of the organic solvent to be used is not particularly limited. For example, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, dibutyl ketone, cyclohexanone; ethanol, butanol, 2-ethylhexyl alcohol, benzyl alcohol, ethylene glycol, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether , Propylene glycol, propylene glycol monomethyl ether, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether and other alcohols and ethers containing hydroxyl groups; ethyl acetate, butyl acetate, ethylene glycol monobutyl ether acetate and other esters; toluene, xylene Aromatic hydrocarbons etc. Illustration can, it is possible to use one or more of these. Of these, ketone-based or ether-based solvents are particularly preferred from the standpoints of solubility with an epoxy resin and film-forming properties.

The blending ratio of the high molecular weight epoxy group-containing resin and the active hydrogen-containing compound (K) composed of a hydrazine derivative (L) in which some or all of the compounds have active hydrogen is a solid content ratio and the high molecular weight epoxy group-containing resin 100 The active hydrogen-containing compound (K) is preferably 0.5 to 20 parts by mass, particularly preferably 1.0 to 10 parts by mass with respect to parts by mass.
The blending ratio of the high molecular weight epoxy group-containing resin and the active hydrogen-containing compound (K) is the ratio between the number of active hydrogen groups in the active hydrogen-containing compound (K) and the number of epoxy groups in the high molecular weight epoxy group-containing resin. It is appropriate from the viewpoint of corrosion resistance and the like that [the number of active hydrogen groups / the number of epoxy groups] is 0.01 to 10, more preferably 0.1 to 8, and still more preferably 0.2 to 4.
Moreover, the ratio of the hydrazine derivative (L) having active hydrogen in the active hydrogen-containing compound (K) is 10 to 100 mol%, more preferably 30 to 100 mol%, still more preferably 40 to 100 mol%. Is appropriate. If the ratio of the hydrazine derivative (L) having active hydrogen is less than 10 mol%, the upper layer film cannot be provided with a sufficient rust prevention function, and the resulting rust prevention effect is simply mixing the film-forming organic resin and the hydrazine derivative. It is no different from the case of using it.

  The coating composition for an upper film of the present invention contains a high molecular weight epoxy group-containing resin (D) as an essential component, but a curing agent capable of reacting with a hydroxyl group in the high molecular weight epoxy group-containing resin ( By containing H), the film is crosslinked at the time of heat-drying after coating, and a film having a dense barrier property with better workability can be formed. As a curing method for forming a resin composition film, a curing method using a urethanization reaction between a polyisocyanate compound (J) and a hydroxyl group in an epoxy group-containing resin, an amino resin (I) and an epoxy group-containing resin A curing method using an etherification reaction with a hydroxyl group can be mentioned as a preferable one.

  Examples of the amino resin (I) include methylol obtained by reacting an amino component such as melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine, and dicyandiamide with an aldehyde component such as formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde. An amino acid resin is mentioned. Those obtained by etherifying the methylol group of this methylolated amino resin with a lower alcohol having 1 to 6 carbon atoms are also included in the amino resin.

Further, among the amino resins, a part or all of the methylol group of the methylol melamine resin is a methyl ether melamine resin etherified with methyl alcohol, a butyl ether melamine resin butyl etherified with butyl alcohol, or methyl alcohol. Particularly preferred is a mixed etherified melamine resin of methyl ether and butyl ether etherified with both of butyl alcohol. Among these, by using a methyl etherified melamine resin containing 1 or more, preferably 1.5 or more imino groups in one molecule, a low temperature with a high molecular weight epoxy group-containing resin (D). The reactivity is improved, and the toughness of the film can be greatly improved. Specific examples of commercially available products include, for example, Cymel 325, Cymel 327, Cymel 703 (all trade names) manufactured by Mitsui Cytec.
The above amino resins can be used individually by 1 type or in mixture of 2 or more types.

  Examples of the polyisocyanate compound (J) include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; cycloaliphatic diisocyanates such as hydrogenated xylylene diisocyanate and isophorone diisocyanate; Aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate; triphenylmethane-4,4 ', 4 "-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-tri Organic polyisocyanates such as polyisocyanate compounds having three or more isocyanate groups, such as isocyanatotoluene and 4,4'-dimethyldiphenylmethane-2,2 ', 5,5'-tetraisocyanate Or the adduct of each of these organic polyisocyanates with a polyhydric alcohol, a low molecular weight polyester resin or water, or a cyclized polymer of each of the above organic polyisocyanates, further, an isocyanurate body, Biuret bodies can be mentioned.

  Furthermore, among them, a polyisocyanate compound having 4 or more, particularly preferably 6 to 10 isocyanate groups in one molecule is a high molecular weight epoxy group-containing resin (D) even when the reaction temperature is lowered. )), A tough film can be formed, and the corrosion resistance of the processed part when subjected to severe processing can be made particularly good. Examples of such a polyisocyanate compound include adducts of 4,4′-dimethyldiphenylmethane-2,2 ′, 5,5′-tetraisocyanate, adducts of hexamethylene diisocyanate, and the like.

The polyisocyanate compound (J) may be obtained by blocking part or all of the isocyanate groups of the polyisocyanate compound with a blocking agent. Examples of the blocking agent include phenols such as phenol, cresol and xylenol; Lactams such as caprolactam, δ-valerolactam, γ-butyrolactam, β-propiolactam; methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, ethylene glycol monoethyl Alcohols such as ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, benzyl alcohol; formamide Oximes such as shim, acetaldoxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime; active methylenes such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, methyl acetoacetate, etc. A blocking agent can be mentioned.
Specific examples of commercial products of polyisocyanate compounds containing four or more isocyanate groups in one molecule include, for example, MF-B80M, MF-B60X, MF-K60X, ME20-B80S (all products manufactured by Asahi Kasei Corporation) Name).

As content of the said hardening | curing agent (H) in the coating composition for upper layer membrane | film | coats, 1-50 mass parts with respect to solid content of 100 mass parts of high molecular weight epoxy group containing resin (D), Preferably it is 5-30 masses. It is suitable from the viewpoint of curability.
The high molecular weight epoxy group-containing resin (D) is sufficiently cross-linked by the addition of the cross-linking agent (curing agent) as described above. However, in order to further increase the low-temperature cross-linking property, a known curing accelerating catalyst may be used. desirable. Examples of the curing accelerating catalyst include N-ethylmorpholine, dibutyltin dilaurate, cobalt naphthenate, stannous chloride, zinc naphthenate, and bismuth nitrate.
In addition, for the purpose of slightly improving physical properties such as adhesion, a known resin such as acrylic, alkyd, or polyester can be mixed and used together with the high molecular weight epoxy group-containing resin (D).

In the upper layer film (coating composition (Y)), if necessary, a solid lubricant can be blended for the purpose of improving the workability of the film.
Examples of the solid lubricant applicable to the present invention include the following, and one or more of these can be used.
(1) Polyolefin wax, paraffin wax: For example, polyethylene wax, synthetic paraffin, natural paraffin, micro wax, chlorinated hydrocarbon, etc. (2) Fluororesin fine particles: For example, polyfluoroethylene resin (polytetrafluoroethylene resin, etc.) , Polyvinyl fluoride resin, polyvinylidene fluoride resin, etc.

In addition, fatty acid amide compounds (eg, stearic acid amide, palmitic acid amide, methylene bis stearoamide, ethylene bis stearoamide, oleic acid amide, esylic acid amide, alkylene bis fatty acid amide), metal Soaps (eg, calcium stearate, lead stearate, calcium laurate, calcium palmitate, etc.), metal sulfides (eg, molybdenum disulfide, tungsten disulfide, etc.), graphite, graphite fluoride, boron nitride, polyalkylene glycol, You may use 1 type, or 2 or more types, such as an alkali metal sulfate.
Among the above solid lubricants, polyethylene wax and fluororesin fine particles (in particular, polytetrafluoroethylene resin fine particles) are particularly suitable.
It is preferable that the compounding quantity of a solid lubricant shall be 1-30 mass parts in the ratio of solid content with respect to 100 mass parts of solid content of the resin composition in coating composition (Y). If the blending amount of the solid lubricant is less than 1 part by mass, the lubricating effect is poor. On the other hand, if the blending amount exceeds 30 parts by mass, the paintability is lowered, which is not preferable.

  In order to obtain particularly excellent processability, a composite (solid) lubricant containing a polyethylene lubricant (generally polyethylene wax) and a polytetrafluoroethylene lubricant (generally polytetrafluoroethylene resin fine particles) ( It is preferable to blend E). This composite (solid) lubricant (E) comprises a polyethylene lubricant (e1) and a polytetrafluoroethylene lubricant (e2) in a ratio (mass) of (e1) / (e2) = 5/5 to 1/9. Ratio). By using such a composite lubricant (E), particularly excellent workability can be obtained as compared with the case where each solid lubricant is used alone. Here, when the ratio (mass ratio) of (e1) / (e2) is out of the range of 5/5 to 1/9, the workability improvement effect cannot be sufficiently obtained due to the combination of both lubricants. Not much different from the case of single addition.

The polyethylene lubricant (e1) preferably has a melting point of 100 to 130 ° C. If the melting point is less than 100 ° C. or more than 130 ° C., the workability obtained by combining both lubricants is lowered. The polytetrafluoroethylene-based lubricant (e2) preferably has an average particle size of 1 to 7 μm. If the particle size is less than 1 μm, the workability obtained by combining both lubricants is reduced, while if it exceeds 7 μm, the lubricant is easily removed from the organic coating layer, and the workability is lowered, which is not preferable.
Examples of the polyethylene lubricant (e1) include Clariant 9615A, 3715, 3620, 3910 (all trade names) manufactured by Clariant, Sun wax 131-P manufactured by Sanyo Chemical Co., Ltd., 161- Use P (all trade names), Chemipearl W-100, W-200, W-500, W-800, W-800, W-950 (all trade names) manufactured by Mitsui Petrochemical Co., Ltd. Can do.

Examples of the polytetrafluoroethylene-based lubricant (e2) include Lubron L-2 and L-5 (both trade names) manufactured by Daikin Industries, Ltd., MP1100 manufactured by Mitsui DuPont Co., Ltd., MP1200 (all trade names), Fullon L150J manufactured by Asahi Glass Co., Ltd., L155J (all trade names) and SST-3 (trade name) manufactured by Shamrock are suitable.
It is preferable that the compounding quantity of a composite lubricant (E) shall be 10-30 mass parts in the ratio of solid content with respect to 100 mass parts of solid content of the resin composition in coating composition (Y). If the blending amount of the solid lubricant is less than 10 parts by mass, the lubricating effect is poor. On the other hand, if the blending amount exceeds 30 parts by mass, the paintability is unfavorable.
In addition, you may mix | blend suitably 1 type or more of the other solid lubricant mentioned above with the composite lubricant (E) as needed.

In the upper layer film (coating composition (Y)), for the purpose of improving the corrosion resistance, a non-chromium rust preventive additive (G) can be contained as necessary. By including such a non-chromium-based anticorrosive additive in the upper layer film, more excellent anticorrosion performance (self-repairability) can be obtained.
As this non-chromium rust preventive additive (G), it is particularly preferable to use one or more selected from the following (g1) to (g5).
(G1) silicon oxide (g2) calcium compound (g3) phosphate compound (g4) molybdate compound (g5) one or more organic compounds selected from triazoles, thiols, thiadiazoles, thiazoles, thiurams

Details of these (g1) to (g5) non-chromium rust preventive additives and anticorrosion mechanisms are as follows.
First, as the component (g1), colloidal silica or dry silica, which is fine particle silica, can be used. From the viewpoint of corrosion resistance, calcium ion-exchanged silica in which calcium is bonded to the surface is used. Is desirable.
As colloidal silica, for example, SNOWTEX O, 20, 30, 40, C, S (all trade names) manufactured by Nissan Chemical Co., Ltd. can be used, and as fumed silica, Nippon Aerosil ( AEROSIL R971, R812, R811, R974, R202, R805, 130, 200, 300, 300CF (all trade names) manufactured by Co., Ltd. can be used. As calcium ion exchange silica, WRGrace & Co. SHIELDEX C303, SHIELDEX AC3, SHIELDEX AC5 (all are trade names) manufactured by SHIELDEX, SHIELDEX SY710 (all are trade names) manufactured by Fuji Silysia Chemical Co., Ltd., and the like can be used. These silicas contribute to the production of dense and stable zinc corrosion products in a corrosive environment, and the corrosion products are formed densely on the plating surface, thereby suppressing the promotion of corrosion.

In addition, the above components (g2) and (g3) exhibit particularly excellent anticorrosion performance (self-repairing property) due to precipitation.
The calcium compound as the component (g2) may be any of calcium oxide, calcium hydroxide, and calcium salt, and one or more of these can be used. In addition, there are no particular restrictions on the type of calcium salt. In addition to simple salts containing only calcium as a cation such as calcium silicate, calcium carbonate, and calcium phosphate, calcium and calcium such as calcium phosphate / zinc, calcium phosphate / magnesium, etc. Double salts containing other cations may be used. This (g2) component is preferentially dissolved in the base metal over zinc and aluminum, which are plating metals, in a corrosive environment, and this seals the defective part as a dense and sparingly soluble product with OH ⁻ produced by the cathode reaction. And suppress the corrosion reaction. Moreover, when it mix | blends with the above silicas, a calcium ion adsorb | sucks to the surface and neutralizes a surface charge electrically and aggregates. As a result, a dense and sparingly soluble protective film is formed to block the corrosion and suppress the corrosion reaction.

  Moreover, a phosphate can be used as a phosphoric acid compound which is said (g3). This phosphate includes all kinds of salts such as simple salts and double salts. Moreover, there is no limitation in the metal cation which comprises it, and any metal cation, such as zinc phosphate, magnesium phosphate, calcium phosphate, and aluminum phosphate, may be used. Further, there is no limitation on the skeleton or the degree of condensation of phosphate ions, and any of normal salt, dihydrogen salt, monohydrogen salt or phosphite may be used. In addition, orthophosphate may be polyphosphate other than orthophosphate. Includes all condensed phosphates such as salts. In this phosphate compound, zinc or aluminum of the plating metal eluted by corrosion forms a dense and sparingly soluble protective film by a complexing reaction with phosphate ions dissociated by hydrolysis, thereby blocking the corrosion starting point, Suppresses the reaction.

  As the molybdate compound (g4), for example, molybdate can be used. The molybdate is not limited in its skeleton and degree of condensation, and examples thereof include orthomolybdate, paramolybdate, and metamolybdate. Moreover, all salts, such as a single salt and a double salt, are included, and a phosphomolybdate etc. are mentioned as a double salt. Molybdate compounds exhibit self-repairing properties due to the passivating effect. That is, by forming a dense oxide on the plating film surface together with dissolved oxygen in a corrosive environment, the corrosion starting point is blocked and the corrosion reaction is suppressed.

  Examples of the organic compound (g5) include the following. That is, as triazoles, 1,2,4-triazole, 3-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole, 5-amino-3-mercapto-1,2 1,4-triazole, 1H-benzotriazole, etc., and as thiols, 1,3,5-triazine-2,4,6-trithiol, 2-mercaptobenzimidazole, etc., and as thiadiazoles, 5- Amino-2-mercapto-1,3,4-thiadiazole, 2,5-dimercapto-1,3,4-thiadiazole and the like, and as thiazoles, 2-N, N-diethylthiobenzothiazole, 2-mercapto Examples include benzothiazoles, and examples of thiurams include tetraethylthiuram disulfide. It is. These organic compounds exhibit self-repairing properties due to the adsorption effect. That is, zinc and aluminum eluted by corrosion are adsorbed on polar groups containing sulfur contained in these organic compounds to form an inert film, thereby blocking the corrosion starting point and suppressing the corrosion reaction.

The blending amount of the non-chromium-based rust preventive additive (G) is 0.1 to 50 parts by mass, preferably 100 to 50 parts by mass of the solid content of the resin composition in the coating composition (Y). Is suitably 0.5 to 30 parts by mass. If the blending amount of the non-chromium rust preventive additive (G) is less than 0.1 parts by mass, the effect of improving the corrosion resistance after alkaline degreasing cannot be sufficiently obtained. In addition, not only the weldability decreases, but also the corrosion resistance tends to decrease.
In addition, two or more kinds of the anticorrosive additives (g1) to (g5) may be added in combination. In this case, since the inherent anticorrosive action is combined, higher corrosion resistance can be obtained. In particular, calcium ion-exchanged silica is used as the component (g1) and one or more of the components (g3), (g4), and (g5), particularly preferably the components (g3) to (g5). When all are added in combination, particularly excellent corrosion resistance is obtained.

Further, in the upper film (coating composition (Y)), other oxide fine particles (for example, aluminum oxide, zirconium oxide, titanium oxide, cerium oxide, antimony oxide, etc.), phosphomolybdate as corrosion inhibitors. One or more kinds of organic inhibitors (for example, hydrazine and its derivatives, thiol compounds, thiocarbamates, etc.) can be added.
For the upper layer film (coating composition (Y)), if necessary, organic coloring pigments (for example, condensed polycyclic organic pigments, phthalocyanine organic pigments), coloring dyes (for example, organic solvents) may be added as necessary. Soluble azo dyes, water-soluble azo metal dyes, etc.), inorganic pigments (eg titanium oxide, etc.), chelating agents (eg thiols, etc.), conductive pigments (eg, metal powders such as zinc, aluminum, nickel etc., phosphorus 1 type, or 2 or more types, such as an iron fluoride, an antimony dope-type tin oxide, a coupling agent (for example, a silane coupling agent, a titanium coupling agent, etc.), a melamine cyanuric acid adduct, etc. can be added.

Moreover, the coating composition for film formation containing the said main component and an additional component normally contains a solvent (an organic solvent and / or water), and also a neutralizer etc. are added as needed.
The organic solvent is not particularly limited as long as it can dissolve or disperse the high molecular weight epoxy group-containing resin (D) and can be prepared as a coating composition.
The neutralizing agent is blended as necessary to neutralize the high molecular weight epoxy group-containing resin (D) to make it water-based, and the high molecular weight epoxy group-containing resin (D) is a cationic resin. In some cases, acids such as acetic acid, lactic acid and formic acid can be used as neutralizing agents.
The dry film thickness of the upper layer film is 0.3 to 2.0 μm, preferably 0.4 to 1.5 μm. When the film thickness of the upper layer film is less than 0.3 μm, the corrosion resistance is insufficient. On the other hand, when the film thickness exceeds 2.0 μm, the weldability and the electrodeposition coating property are deteriorated.
Further, from the viewpoint of weldability and electrodeposition coating properties, the total film thickness of the surface treatment film of the first layer and the upper film of the second layer is preferably 2.0 μm or less.

In order to produce the surface-treated steel sheet of the present invention as described above, a surface treatment composition (X) (treatment liquid) in which the above-described components are blended on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet. It is applied and dried, and then a coating composition (Y) for forming an upper film containing the above-described components is applied and dried.
As a method of coating the surface treatment composition (X) on the surface of the plated steel plate, any method such as a coating method, a dipping method, a spray method, or the like can be adopted. As a coating method, any method such as a roll coater (3-roll method, 2-roll method, etc.), a squeeze coater, or a die coater may be used. In addition, after the coating process, dipping process or spraying process using a squeeze coater or the like, the coating amount can be adjusted, the appearance can be made uniform, and the film thickness can be made uniform by an air knife method or a roll drawing method.

After coating the surface treatment composition (X), it is usually heated and dried without washing with water. For the heat drying treatment, a dryer, a hot air furnace, a high-frequency induction heating furnace, an infrared furnace, or the like can be used. The heat drying is desirably performed in the range of 30 to 200 ° C., preferably 40 ° C. to 140 ° C., at the ultimate plate temperature. If the heating and drying temperature is less than 30 ° C., a large amount of moisture remains in the film, resulting in insufficient corrosion resistance. In addition, when the heating and drying temperature exceeds 200 ° C., not only is it uneconomical, but there is a possibility that defects occur in the film and the corrosion resistance decreases.
As a method for forming the coating composition (Y), any method such as a coating method, a dipping method, or a spray method can be employed. As a coating method, any method such as a roll coater (3-roll method, 2-roll method, etc.), a squeeze coater, or a die coater may be used. In addition, after the coating process, dipping process or spraying process using a squeeze coater or the like, the coating amount can be adjusted, the appearance can be made uniform, and the film thickness can be made uniform by an air knife method or a roll drawing method.

  After coating the coating composition (Y), it is usually heated and dried without washing with water, but it may be washed with water after application of the coating composition (Y). As the heating and drying means, a dryer, a hot air furnace, a high frequency induction heating furnace, an infrared furnace, or the like can be used, but a high frequency induction heating furnace is particularly preferable from the viewpoint of corrosion resistance. The heat treatment is desirably performed in the range of 50 to 350 ° C., preferably 80 to 250 ° C., at the ultimate plate temperature. When the heating temperature is less than 50 ° C., a large amount of solvent remains in the film, resulting in insufficient corrosion resistance. Further, when the heating temperature exceeds 350 ° C., not only is it uneconomical, but there is a possibility that defects occur in the film and the corrosion resistance is lowered.

The present invention includes a surface-treated steel sheet having a coating as described above on both sides or one side. Therefore, examples of the form of the surface-treated steel sheet according to the present invention include the following.
(1) One side: plating film-surface treatment film-upper layer film, one side: plating film (2) One side: plating film-surface treatment film-upper layer film, one side: plating film-known phosphate treatment film, etc. (3) Both sides: plating film-surface treatment film-upper layer film (4) Single side: plating film-surface treatment film-upper layer film, one side: plating film-surface treatment film (film corresponding to the surface treatment film of the present invention)
(5) One side: plating film-surface treatment film-upper layer film, one side: plating film-organic film (film corresponding to the upper layer film of the present invention)

<Example 1>
[Surface treatment composition for first layer (surface treatment film)]
Titanium-containing aqueous liquids A1 to A7, organic phosphoric acid compounds B1 to B6, inorganic phosphoric acid compounds C1 to C5, and aqueous organic resins F1 to F7 (water-soluble or water-dispersible organic resins) used for the surface treatment composition are as follows. Show. These components were blended in the proportions shown in Tables 2 and 3 to obtain surface treatment compositions P1 to P42.

(1) Production and production example 1 of titanium-containing aqueous liquids A1 to A7
Ammonia water (1: 9) was added dropwise to a solution in which 5 cc of a titanium tetrachloride 60% solution was made 500 cc with distilled water to precipitate titanium hydroxide. After washing with distilled water, 10 cc of a 30% hydrogen peroxide solution was added and stirred to obtain a yellow translucent viscous titanium-containing aqueous liquid A1 containing titanium.
・ Production example 2
A mixture of 10 parts by mass of tetraiso-propoxytitanium and 10 parts by mass of iso-propanol was dropped into a mixture of 10 parts by mass of 30% hydrogen peroxide and 100 parts by mass of deionized water while stirring at 20 ° C. over 1 hour. . Thereafter, the mixture was aged at 25 ° C. for 2 hours to obtain a yellow transparent, slightly viscous titanium-containing aqueous liquid A2.

・ Production Example 3
A titanium-containing aqueous liquid A3 was obtained under the same production conditions as in Production Example 2 except that tetra-n-butoxytitanium was used instead of tetraiso-propoxytitanium used in Production Example 2.
・ Production Example 4
A titanium-containing aqueous liquid A4 was obtained under the same production conditions as in Production Example 2 except that a tetramer of tetraiso-propoxytitanium was used instead of tetraiso-propoxytitanium used in Production Example 2.
・ Production Example 5
A titanium-containing aqueous liquid was produced under the same production conditions as in Production Example 2, except that hydrogen peroxide was used in 3 times the amount of Production Example 2, dropped at 50 ° C over 1 hour, and further aged at 60 ° C for 3 hours. A5 was obtained.

・ Production Example 6
The titanium-containing aqueous liquid A3 produced in Production Example 3 was further heat-treated at 95 ° C. for 6 hours to obtain a white-yellow translucent titanium-containing aqueous liquid A6.
・ Production Example 7
A mixture of 10 parts by mass of tetraiso-propoxytitanium and 10 parts by mass of iso-propanol was mixed with 5 parts by mass of “TKS-203” (trade name, manufactured by Teica, titanium oxide sol), 30% hydrogen peroxide solution 10 The mixture was added dropwise to a mixture of parts by mass and 100 parts by mass of deionized water at 10 ° C. with stirring for 1 hour. Thereafter, the mixture was aged at 10 ° C. for 24 hours to obtain a yellow transparent slightly viscous titanium-containing aqueous liquid A7.

(2) Organophosphate compounds B1 to B6
B1: 1-hydroxymethane-1,1-diphosphonic acid B2: 1-hydroxyethane-1,1-diphosphonic acid B3: 1-hydroxypropane-1,1-diphosphonic acid B4: 2-hydroxyphosphonoacetic acid B5: 3 -Phosphonobutane-1,2,4-tricarboxylic acid B6: Potassium 2-hydroxyphosphonoacetate (3) Inorganic phosphate compounds C1 to C5
C1: 10% orthophosphoric acid C2: 10% metaphosphoric acid C3: tripolyphosphoric acid C4: sodium pyrophosphate C5: ammonium metaphosphate

(4-1) Synthesis / Synthesis Example 1 of water-based organic resins F1 to F4
In a flask equipped with a nitrogen-filled tube, a ball condenser, a dropping funnel and a mechanical stirrer, 200 parts by mass of propylene glycol monomethyl ether was heated to 90 ° C., and then the temperature was maintained at 90 ° C., and styrene was added to the flask. A mixture of 10 parts by mass, 80 parts by mass of tert-butyl acrylate, 10 parts by mass of 2-hydroxyethyl acrylate, and 1 part by mass of azobisisobutyronitrile was added dropwise over 3 hours, and after completion of the addition, maintained at 90 ° C. for 2 hours. Then, it was cooled to room temperature to obtain an aqueous organic resin (acrylic resin solution) F1. The obtained acrylic resin has a Tg (glass transition point) of 33 ° C.
Synthesis example 2
In a flask equipped with a nitrogen-filled tube, a ball condenser, a dropping funnel and a mechanical stirrer, 200 parts by mass of propylene glycol monomethyl ether was heated to 90 ° C., and then the temperature was maintained at 90 ° C., and styrene was added to the flask. A mixture of 25 parts by mass, 60 parts by mass of methyl acrylate, 15 parts by mass of acrylamide and 1 part by mass of azobisisobutyronitrile was added dropwise over 3 hours. After completion of the addition, the mixture was further maintained at 90 ° C. for 2 hours and then cooled to room temperature. Thus, an aqueous organic resin (acrylic resin solution) F2 was obtained. The obtained acrylic resin has a Tg of 46 ° C.

Synthesis example 3
In a flask equipped with a nitrogen-filled tube, a ball condenser, a dropping funnel and a mechanical stirrer, 200 parts by mass of propylene glycol monomethyl ether was heated to 90 ° C., and then the temperature was maintained at 90 ° C., and styrene was added to the flask. A mixture of 55 parts by mass, 5 parts by mass of n-butyl acrylate, 20 parts by mass of 2-hydroxyethyl methacrylate, 20 parts by mass of N-methylacrylamide and 1 part by mass of azobisisobutyronitrile was added dropwise over 3 hours, and the addition was completed. Thereafter, the mixture was further maintained at 90 ° C. for 2 hours, and then cooled to room temperature to obtain an aqueous organic resin (acrylic resin solution) F3. The obtained acrylic resin has a Tg of 78 ° C.
Synthesis example 4
In a flask equipped with a nitrogen-filled tube, a ball condenser, a dropping funnel and a mechanical stirrer, 200 parts by mass of propylene glycol monomethyl ether was heated to 90 ° C., and the temperature was maintained at 90 ° C. A mixture of 80 parts by weight of methacrylate, 10 parts by weight of n-butyl acrylate, 10 parts by weight of 2-hydroxyethyl acrylate, and 1 part by weight of azobisisobutyronitrile is dropped over 3 hours. After being held, it was cooled to room temperature to obtain an aqueous organic resin (acrylic resin solution) F4. The obtained acrylic resin has a Tg of 56 ° C.

(4-2) Water-based organic resins F5 to F7
F5: “Superflex E-2500” (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., water-based polyurethane resin)
F6: “Vaironal MD-1100” (trade name, manufactured by Toyobo Co., Ltd., water-based polyester resin)
F7: “Adeka Resin EM-0718” (trade name, manufactured by ADEKA Corporation, water-based epoxy resin)

[Coating composition for second layer (upper layer film)]
As for the coating composition for the upper layer film, the resin composition shown in Table 4 and Table 5 is used, and a non-chromium rust preventive additive (Table 6) is appropriately blended therein, and a coating disperser (sand grinder) is used. ) Was used for a predetermined time to prepare a coating composition.
The base resins (reaction products) of the resin compositions shown in Table 4 and Table 5 were synthesized as follows.

<Synthesis Example 1>
634 parts of jER828 (Japan Epoxy Resin, Epoxy Equivalent 187), 366 parts of bisphenol A, 8 parts of 50% tetraethylammonium bromide aqueous solution and 180 parts of cyclohexanone were charged into a four-necked flask and heated to 150 ° C. and reacted for 5 hours. Then, 300 parts of methyl isobutyl ketone and 1843 parts of cyclohexanone were added while cooling to obtain an epoxy resin solution M1 (resin composition (1)) having a solid content of 30%. The number average molecular weight of this resin was 7600.
<Synthesis Example 2>
347 parts of jER1256 (Japan Epoxy Resin, epoxy equivalent 7880) and 543 parts of cyclohexanone were charged into a four-necked flask, heated to 130 ° C., and completely dissolved the epoxy resin in 2 hours. This was cooled to 120 ° C., 3.7 parts of 3-amino-1,2,4-triazole (molecular weight 84) was added and reacted for 6 hours until the epoxy group disappeared. 78 parts of ketone and 197 parts of cyclohexanone were added to obtain a triazole-modified epoxy resin solution M2 (resin composition (2)) having a solid content of 30%. The number average molecular weight of this resin was 10100.

<Synthesis Example 3>
637 parts of jER828 (manufactured by Japan Epoxy Resin Co., Epoxy Equivalent 187), 363 parts of bisphenol A, 10 parts of 50% tetraethylammonium bromide aqueous solution and 175 parts of cyclohexanone were charged into a four-necked flask and heated to 160 ° C. and reacted for 4 hours. An epoxy resin solution having a solid content of 85% was obtained. To this, 1315 parts of cyclohexanone was added and then cooled to 100 ° C., 9.7 parts of 3,5-dimethylpyrazole and 13 parts of dibutylamine were added and reacted for 6 hours until the epoxy group disappeared. While adding 908 parts of methyl isobutyl ketone, a 30% solid content pyrazole-modified epoxy resin solution M3 (resin composition (3)) was obtained. The number average molecular weight of this resin was 6300.
<Synthesis Example 4>
jER828 (manufactured by Japan Epoxy Resin Co., Ltd., epoxy equivalent 187), 1833 parts, 894 parts of bisphenol A, 1.96 parts of tetraethylammonium bromide and 294 parts of methyl isobutyl ketone were charged into a four-necked flask and heated to 140 ° C. for 4 hours. While cooling, 3795 parts of ethylene glycol monobutyl ether was added to obtain an epoxy resin solution M4 (resin composition (4)) having an epoxy equivalent of 1388 and a solid content of 40%. The number average molecular weight of this resin was 3100.

[Manufacture of surface-treated steel sheets]
The plated steel sheet shown in Table 1, which is a plated steel sheet for home appliances, building materials, and automobile parts based on cold-rolled steel sheets, was used as a processing original sheet. In addition, the thing of predetermined | prescribed board thickness was employ | adopted for the board thickness of the steel plate according to the objective of evaluation. After the surface of this plated steel sheet was subjected to alkali degreasing treatment, washed with water and dried, the surface treatment composition for forming the first layer was applied with a roll coater and dried by heating at various temperatures. The film thickness of the film was adjusted by the solid content (heating residue) of the surface treatment composition or coating conditions (rolling force of the roll, rotation speed, etc.).
Next, the coating composition for forming the second layer was applied by a roll coater and dried by heating at various temperatures. The film thickness of the film was adjusted by the solid content (heating residue) of the coating composition or application conditions (rolling force of roll, rotation speed, etc.).

Tables 7 to 10 show the results of evaluating the film composition and quality performance (corrosion resistance, corrosion resistance after alkaline degreasing, corrosion resistance after processing, weldability, electrodeposition coating property, adhesive bondability) of the obtained surface-treated steel sheet. The quality performance was evaluated as follows.
(1) Corrosion resistance About each sample, the following combined cycle test (CCT) was given, and the white rust generation | occurrence | production area ratio and red rust generation | occurrence | production area ratio after 81-cycle progress evaluated.
Salt spray (based on JIS-Z-2371): 2 hours ↓
Dry (60 ° C): 4 hours ↓
Wet (50 ° C., ≧ 95% RH): 2 hours The evaluation criteria are as follows.
◎: White rust generation area ratio less than 5% ○ +: White rust generation area ratio of 5% or more and less than 10% ○: White rust generation area ratio of 10% or more and less than 30%, no red rust generation Red rust is not generated when the area ratio is 30% or more. △: Red rust is generated, Red rust generation area ratio is less than 10% ×: Red rust generation area ratio is 10% or more

(2) Corrosion resistance after alkaline degreasing Each sample was degreased under the conditions of spray treatment at 60 ° C for 2 minutes using "FC-4460" manufactured by Nippon Parker Lines Co., Ltd., and then subjected to the following combined cycle test (CCT) And the white rust generation area ratio and red rust generation area ratio after 81 cycles were evaluated.
Salt spray (based on JIS-Z-2371): 2 hours ↓
Dry (60 ° C): 4 hours ↓
Wet (50 ° C., ≧ 95% RH): 2 hours The evaluation criteria are as follows.
◎: White rust generation area ratio less than 5% ○ +: White rust generation area ratio of 5% or more and less than 10% ○: White rust generation area ratio of 10% or more and less than 30%, no red rust generation Red rust is not generated when the area ratio is 30% or more. △: Red rust is generated, Red rust generation area ratio is less than 10% ×: Red rust generation area ratio is 10% or more

(3) Corrosion resistance after processing For each sample, deformation and sliding were added with a draw bead according to the following conditions, and this sample was subjected to spray treatment at 60 ° C. for 2 minutes using “FC-4460” manufactured by Nihon Parkerizing Co., Ltd. After degreasing under the conditions, the CCT performed in “(1) Corrosion resistance” was performed, and the white rust generation area ratio and the red rust generation area ratio after 42 cycles were evaluated.
Pressing load: 800kgf
Drawing speed: 1000mm / min
Bead shoulder R: male side 2mmR, female side 3mmR
Pushing depth: 7mm
Oil used: “Preton R-352L” manufactured by Sugimura Chemical Co., Ltd.
The evaluation criteria are as follows.
◎: White rust generation area ratio less than 5% ○ +: White rust generation area ratio of 5% or more and less than 10% ○: White rust generation area ratio of 10% or more and less than 30%, no red rust generation Red rust is not generated when the area ratio is 30% or more. △: Red rust is generated, Red rust generation area ratio is less than 10% ×: Red rust generation area ratio is 10% or more

(4) Weldability For each sample, a welding test with continuous spotting was performed under the conditions of electrode used: CF-type Cr—Cu electrode, applied pressure: 200 kgf, energization time: 10 cycles / 50 Hz, welding current: 10 kA. The score was evaluated. The evaluation criteria are as follows.
◎: 2000 points or more ○: 1000 points or more, less than 2000 points △: 500 points or more, less than 1000 points ×: Less than 500 points (5) Electrodeposition coating property Cationic electrodeposition paint (manufactured by Kansai Paint Co., Ltd.) After coating “GT-10”) to a film thickness of 30 μm, baking was performed at 170 ° C. for 20 minutes. The coated sample was immersed in warm water at 40 ° C. for 240 hours, immediately cut into grids (10 × 10, 1 mm interval), attached and peeled off with adhesive tape, and the peeled area ratio of the coating film was measured. . The evaluation criteria are as follows.
◎: No peeling ○: Peeling area ratio less than 5% △: Peeling area ratio of 5% or more, less than 20% ×: Peeling area ratio of 20% or more

(6) Adhesive bondability Each sample was sheared to 25 mm × 200 mm, and 1 g / m ² of cleaning oil (“Preton 303P” manufactured by Sugimura Chemical Co., Ltd.) was applied to the surface. After standing for one day, apply the adhesive ("Macroplast PV5308" manufactured by Cemedine Henkel) to a range of 25mm x 150mm of the sample, and overlap the other sample with three 0.15mm piano wires sandwiched between them. , Fixed with clips. A baking treatment was performed at 170 ° C. for 20 minutes, and the sample was left standing for one day to prepare a sample. A 25 mm × 50 mm portion to which no adhesive was applied was bent at 90 degrees, and a T peel test was conducted with a tensile tester at 200 mm / min, and the peel strength at that time was measured. The evaluation criteria are as follows.
◎: 125N / 25mm or more ○: 118N / 25mm or more, less than 125N / 25mm △: 80N / 25mm or more, less than 118N / 25mm ×: Less than 80N / 25mm

In Tables 2 and 3, * 1 to * 5 indicate the following contents.
* 1 Titanium-containing aqueous liquids A1 to A7 described in the main text of the specification
* 2 Organophosphate compounds B1 to B6 described in the specification text
* 3 Inorganic phosphate compounds C1 to C5 described in the specification text
* 4 Water-soluble or water-dispersible organic resins F1 to F7 described in the main text of the specification
* 5 Mass parts of solid content

In Tables 7 to 10, * 1 to * 5 indicate the following contents.
* 1 Plated steel plate No. 1-No. 9
* 2 Surface treatment compositions P1 to P42 described in Tables 2 and 3
* 3 Resin composition Nos. Listed in Tables 4 and 5 1-No. 23
* 4 Rust prevention additive No. described in Table 6 1-No. 7
* 5 Mass parts of solid content

<Example 2>
[Coating composition for second layer (upper layer film)]
A non-chromium antirust additive (Table 6) and a solid lubricant (Table 11) are appropriately blended into the resin compositions shown in Tables 4 and 5, and stirred for a predetermined time using a paint disperser (sand grinder). Then, a surface treatment composition was prepared.

[Manufacture of surface-treated steel sheets]
The plated steel sheet shown in Table 1, which is a plated steel sheet for home appliances, building materials, and automobile parts based on cold-rolled steel sheets, was used as a processing original sheet. In addition, the thing of predetermined | prescribed board thickness was employ | adopted for the board thickness of the steel plate according to the objective of evaluation. After the surface of this plated steel sheet was subjected to alkaline degreasing treatment, washed with water and dried, the surface treatment composition for forming the first layer described in Example 1 was applied with a roll coater and dried by heating at various temperatures. The film thickness of the film was adjusted by the solid content (heating residue) of the surface treatment composition or coating conditions (rolling force of the roll, rotation speed, etc.).

Next, the coating composition for forming the second layer was applied by a roll coater and dried by heating at various temperatures. The film thickness of the film was adjusted by the solid content (heating residue) of the coating composition or application conditions (rolling force of roll, rotation speed, etc.).
Table 12 shows the results of evaluating the film composition and quality performance (corrosion resistance, corrosion resistance after alkaline degreasing, corrosion resistance after processing, weldability, electrodeposition coating property, adhesive bondability) of the obtained surface-treated steel sheet. The quality performance was evaluated as follows.

(1) Corrosion resistance About each sample, the following combined cycle test (CCT) was given, and it evaluated by the white rust generation | occurrence | production area rate and red rust generation | occurrence | production area rate after 90 cycles progress.
Salt spray (based on JIS-Z-2371): 2 hours ↓
Dry (60 ° C): 4 hours ↓
Wet (50 ° C., ≧ 95% RH): 2 hours The evaluation criteria are as follows.
◎: White rust generation area ratio less than 5% ○ +: White rust generation area ratio of 5% or more and less than 10% ○: White rust generation area ratio of 10% or more and less than 30%, no red rust generation Red rust is not generated when the area ratio is 30% or more. △: Red rust is generated, Red rust generation area ratio is less than 10% ×: Red rust generation area ratio is 10% or more

(2) Corrosion resistance after alkaline degreasing Each sample was degreased under the conditions of spray treatment at 60 ° C for 2 minutes using "FC-4460" manufactured by Nippon Parker Lines Co., Ltd., and then subjected to the following combined cycle test (CCT) And the white rust generation area ratio and the red rust generation area ratio after 90 cycles were evaluated.
Salt spray (based on JIS-Z-2371): 2 hours ↓
Dry (60 ° C): 4 hours ↓
Wet (50 ° C., 95% RH): 2 hours The evaluation criteria are as follows.
◎: White rust generation area ratio less than 5% ○ +: White rust generation area ratio of 5% or more and less than 10% ○: White rust generation area ratio of 10% or more and less than 30%, no red rust generation Red rust is not generated when the area ratio is 30% or more. △: Red rust is generated, Red rust generation area ratio is less than 10% ×: Red rust generation area ratio is 10% or more

(3) Corrosion resistance after processing For each sample, deformation and sliding were added with a draw bead according to the following conditions, and this sample was subjected to spray treatment at 60 ° C. for 2 minutes using “FC-4460” manufactured by Nihon Parkerizing Co., Ltd. After degreasing under the conditions, the CCT performed in “(1) Corrosion resistance” was performed, and the white rust generation area ratio and red rust generation area ratio after 48 cycles were evaluated.
Pressing load: 800kgf
Drawing speed: 1000mm / min
Bead shoulder R: male side 2mmR, female side 3mmR
Pushing depth: 7mm
Oil used: “Preton R-352L” manufactured by Sugimura Chemical Co., Ltd.
The evaluation criteria are as follows.
◎: White rust generation area ratio less than 5% ○ +: White rust generation area ratio of 5% or more and less than 10% ○: White rust generation area ratio of 10% or more and less than 30%, no red rust generation Red rust is not generated when the area ratio is 30% or more. △: Red rust is generated, Red rust generation area ratio is less than 10% ×: Red rust generation area ratio is 10% or more

(4) Weldability The same as in Example 1.
(5) Electrodeposition paintability Same as Example 1.
(6) Adhesive bondability Same as Example 1.

In Table 12, * 1 to * 7 indicate the following contents.
* 1 Plated steel plate No. 1-No. 8
* 2 Surface treatment compositions P1 to P42 described in Tables 2 and 3
* 3 Resin composition Nos. Listed in Tables 4 and 5 1-No. 23
* 4 Rust prevention additive No. described in Table 6 1-No. 7
* 5 Solid lubricant no. 1-No. 9
* 6 Mass part of solid content * 7 Mass ratio

Claims (13)

At least one titanium selected from a hydrolyzable titanium compound, a hydrolyzable titanium compound low condensate, titanium hydroxide, and a titanium hydroxide low condensate on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet 1 to 400 parts by mass of an organic phosphoric acid compound (B) and an inorganic phosphoric acid compound (C) with respect to 100 parts by mass of the solid content of the titanium-containing aqueous liquid (A) obtained by mixing the compound with hydrogen peroxide. Is formed by applying and drying a surface treatment composition (X) containing 50 to 150 parts by weight (excluding a surface treatment composition containing a vanadic acid compound, a zirconium fluoride compound and a zirconium carbonate compound) It has a surface-treated film having a film thickness of 0.01 to 1.0 μm, and an upper layer thereof contains a high molecular weight epoxy group-containing resin (D) having a number average molecular weight of 6000 to 20000. A highly corrosion-resistant surface-treated steel sheet having an upper film having a film thickness of 0.3 to 2.0 μm formed by applying and drying the coating composition (Y).   The coating composition (Y) further comprises a polyethylene lubricant (e1) and a polytetrafluoroethylene lubricant (e2) in a ratio (mass ratio) of (e1) / (e2) = 5/5 to 1/9. The high corrosion resistance surface-treated steel sheet according to claim 1, comprising a composite lubricant (E) contained in   The coating composition (Y) contains 10 to 30 parts by mass of the composite lubricant (E) in a ratio of the solid content to 100 parts by mass of the solid content of the resin composition. High corrosion resistance surface-treated steel sheet.   The highly corrosion-resistant surface-treated steel sheet according to claim 2 or 3, wherein the melting point of the polyethylene-based lubricant (e1) in the composite lubricant (E) is 100 to 130 ° C.   The high corrosion resistance surface-treated steel sheet according to any one of claims 2 to 4, wherein the polytetrafluoroethylene-based lubricant (e2) in the composite lubricant (E) has an average particle size of 1 to 7 µm.   In the surface treatment composition (X), the water-soluble organic resin and / or the water-dispersible organic resin (F) is 2000 mass in terms of the solid content with respect to 100 mass parts of the solid content of the titanium-containing aqueous liquid (A). The highly corrosion-resistant surface-treated steel sheet according to any one of claims 1 to 5, wherein the highly corrosion-resistant surface-treated steel sheet is contained.   The coating composition (Y) further contains 0.1 to 50 parts by mass of the non-chromium rust preventive additive (G) in a ratio of solid content to 100 mass parts of solid content of the resin composition. The highly corrosion-resistant surface-treated steel sheet according to any one of claims 1 to 6. The coating composition (Y) contains at least one selected from the following (g1) to (g5) as the non-chromium-based anticorrosive additive (G). Corrosion-resistant surface-treated steel sheet.
(G1) silicon oxide (g2) calcium compound (g3) phosphoric acid compound (g4) molybdate compound (g5) one or more selected from triazoles, thiols, thiadiazoles, thiazoles, thiurams, S Organic compounds containing atoms   The coating composition (Y) further has a curing agent (H) having a group that crosslinks with a hydroxyl group in a proportion of 1 to 50 mass in terms of solid content with respect to 100 mass parts of the solid content of the high molecular weight epoxy group-containing resin (D). The highly corrosion-resistant surface-treated steel sheet according to any one of claims 1 to 8, which is contained in a part.   The highly corrosion-resistant surface-treated steel sheet according to claim 9, wherein the curing agent (H) having a group capable of crosslinking with a hydroxyl group is an amino resin (I) having an average of one or more imino groups in one molecule.   The highly corrosion-resistant surface-treated steel sheet according to claim 9, wherein the curing agent (H) having a group capable of crosslinking with a hydroxyl group is a polyisocyanate compound (J) having an average of 4 or more isocyanate groups in one molecule. .   The high-corrosion-resistant surface-treated steel sheet according to claim 11, wherein the polyisocyanate compound (J) has at least a part of isocyanate groups blocked with a blocking agent.     Modified epoxy in which the high molecular weight epoxy group-containing resin (D) in the coating composition (Y) is modified with an active hydrogen-containing compound (K) comprising a hydrazine derivative (L) in which some or all of the compounds have active hydrogen The highly corrosion-resistant surface-treated steel sheet according to any one of claims 1 to 12, which is a group-containing resin.