JPH07242833A - Aqueous coating composition excellent in corrosion resistance and solvent resistance - Google Patents

Abstract

PURPOSE:To obtain an aqueous coating composition forming a coating film having excellent corrosion resistance and solvent resistance on a metal material. CONSTITUTION:The characteristic of this aqueous coating composition forming a coating film having excellent corrosion resistance and solvent resistance comprises containing (a) one or two or more kinds of a resin components selected from a water-soluble or water-dispersible urethane resin, epoxy resin, polyester resin and acrylic resin, composed of at least one side chain having 200-5000 molecular weight and a main skeleton chain having >=1000 molecular weight and having 55 ratio of (molecular weight of a main skeleton chain)/(total molecular weight of side chains), (b) a curing agent component and (c) a silica component so that a ratio of solid content [a+b] of the components (a) and (b) to total solid content [a+b+c] is 50-97wt.% and a ratio of solid content [c] of the component (c) to total solid content [a+b+c] is 3-50wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous coating composition having excellent corrosion resistance (corrosion resistance) and solvent resistance. More specifically, the present invention relates to an aqueous coating composition which forms a coating film having excellent corrosion resistance and solvent resistance on the surface of a metal material.

[0002]

2. Description of the Related Art In recent years, a functional surface-treated steel sheet having excellent corrosion resistance obtained by subjecting a surface of a zinc- or zinc-based alloy-plated steel sheet to a chromate treatment and further forming and coating an organic resin film thereon, Developed and widely used.

As conventional techniques relating to this functional surface-treated steel sheet, there are (1) JP-A-03-57639, (2) JP-A-04-6280, and (3) JP-A-62-152578.
No. 4, (4) JP-A-63-99938, (5) JP-A-0.
3-17189, and (6) Japanese Patent Laid-Open No. 04-288878.
The following techniques are disclosed in the issue.

(1) Japanese Patent Application Laid-Open No. 03-57639 relates to a coating composition prepared by adding silica to a resin composition obtained by adding an alkanolamine to an epoxy group of a urethane-modified bisphenol A type epoxy resin. The film obtained by using this coating composition was excellent in corrosion resistance and coating adhesion, but was unsatisfactory in the high solvent resistance aimed at by the present invention.

(2) Japanese Unexamined Patent Publication No. 04-6280 discloses a method in which the surface of a zinc-plated steel sheet is subjected to chromate treatment, and an organic film (epoxy-based, urethane-based, acrylic-based resin, etc.) is further formed thereon. It is disclosed. However, the coating film obtained with this component system was not satisfactory with respect to the high corrosion resistance aimed at by the present invention.

(3) JP-A-62-152578 discloses a method in which an aqueous composition containing silicic acid sol is applied to a carboxylated polyolefin resin-epoxy resin mixed system on a metal material and dried at a plate temperature of 60 ° C. or higher. Is disclosed.
This invention utilizes a crosslinking reaction between a carboxyl group and an epoxy group, but is unsatisfactory in the high corrosion resistance and high solvent resistance aimed at by the present invention.

(4) Japanese Patent Laid-Open No. 63-99938 discloses a basic epoxy resin film in which one or two kinds of silica and aluminum phosphomolybdate are mixed with an epoxy resin. Since the cross-linking density of the coating film obtained from this component system is not sufficient, it was unsatisfactory in the high corrosion resistance and high solvent resistance aimed at by the present invention.

(5) Japanese Patent Application Laid-Open No. 03-17189 discloses a resin film in which a urethane-modified polyolefin resin is mixed with fluorine resin particles and silica particles. This was unsatisfactory in the high corrosion resistance aimed at by the present invention because no crosslinking agent was used.

(6) Japanese Patent Application Laid-Open No. 04-288878 discloses a method of coating an acrylic resin, polyethylene resin, epoxy resin, polyester resin or the like on a chromate film containing silica. However, the film thus obtained was unsatisfactory in the high corrosion resistance intended by the present invention.

Generally, the corrosion resistance of the surface-treated steel sheet largely depends on the water resistance and the adhesiveness of the organic resin film. Therefore, in order to improve the water resistance of the resin film, the content of the hydrophobic portion in the resin is increased, or It is necessary to reduce the content of the hydrophilic part as much as possible by using a crosslinking agent. However, if the content of the hydrophobic portion is increased, the resin gels at the stage of making the resin system water-based (dissolving or dispersing), which makes it unusable. On the other hand, when a cross-linking agent is used, a long time and a high reaction temperature are required to perform sufficient cross-linking, but in many cases, the baking time of the surface-treated steel sheet coating is 30 seconds or less, It is difficult to fully exhibit the performance of the resin itself.

Further, when solvent coating is performed after coating with the resin film, the resin film must have solvent resistance. In general, the solvent resistance is also greatly affected by the adhesiveness and crosslink density of the organic resin film.
Generally, in order to improve the solvent resistance of the resin, a three-dimensional network structure is formed in the resin structure by a chemical bond. However, in the case of conventional paints for surface-treated steel sheets, sufficient cross-linking is often not performed, and thus the organic resin film obtained generally has low solvent resistance. Therefore, at present, no water-based coating composition having good corrosion resistance and solvent resistance has been found.

[0012]

As is apparent from the above description of the prior art, in the prior art, a resin film that simultaneously satisfies both excellent corrosion resistance and solvent resistance within a short baking time of 30 seconds or less. No water-based coating composition capable of forming the above is obtained. Also, to improve the coating application work environment,
There is a great demand for water-based solvent-based treatment agents. The present invention is intended to solve the above-mentioned problems of the prior art and provide an aqueous coating composition capable of forming a resin film having excellent corrosion resistance and solvent resistance on a metal material.

[0013]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies on a water-based coating composition capable of forming a resin film on a metal material that simultaneously satisfies both the corrosion resistance and the solvent resistance. As a result, they have found that the above problems can be solved mainly by specifying the skeletal structure of the resin polymer molecule, and have completed the present invention.

That is, the aqueous composition excellent in corrosion resistance and solvent resistance of the present invention is (a) at least one selected from water-soluble or water-dispersible urethane resin, epoxy resin, polyester resin, and acrylic resin. A resin component comprising the above, (b) a curing agent component comprising at least one curing agent for resin component, and (c) an inorganic component comprising silica, The molecule has (i) a main skeleton chain having a molecular weight of 1000 or more;
(Ii) one or more side chains bonded to this main skeleton and having a molecular weight of 200 to 5,000, and the sum of the molecular weights of the side chains of the molecular weight [M _Wi ] of the main skeleton. the ratio [M _Wii] [M _Wi] / [M _Wii] is 5 or less, the resin component (a) and the curing agent component (b)
Of the total solid content weight [a + b] of the component (a),
The content ratio [a + b] / [a + b + c] with respect to the total solid weight [a + b + c] of (b) and (c) is 50 to 97.
% Of the solid content weight [c] of the inorganic component (c),
Content [c] / [a + b + c] of the total solid content [a + b + c] of the components (a), (b) and (c)
Is 3 to 50%.

In the water-based coating composition of the present invention, each side chain of each resin molecule of the resin component (a) is one selected from a bisphenol compound, a polyester compound, an acrylic compound, and an isocyanate compound, and It is preferably a residue formed by a binding reaction with the main skeleton-forming compound.

In the water-based coating composition of the present invention,
It is preferable that the curing agent component (b) contains at least one selected from water-dispersible or water-soluble polyfunctional epoxy resins and isocyanate compounds.

Furthermore, in the water-based coating composition of the present invention, the silica in the inorganic component (c) is 3 to 30 nm.
It is preferably a fine powder having an average particle size of (millimicron).

Further, in the water-based coating composition of the present invention, in addition to the components (a), (b) and (c), one or more polyolefin waxes having a saponification value of 0 or 30 or less are further added. Including a lubricant component (d) including
Of the solid content weight [d] of the lubricant component (d), the total solid content weight [a + b] of the components (a), (b) and (c).
+ C] is preferably 1 to 30%.

[0019]

The structure of the present invention will be described in detail below. The first characteristic of the water-based coating composition of the present invention is that the resin molecule of the resin component has a skeletal structure composed of a main skeleton and one or more side chains bonded to the main skeleton. The resin having a specific skeleton structure is blended in a constant weight ratio. The resin that can be used as a resin component in the present invention needs to be selected from resins having excellent corrosion resistance, solvent resistance, chemical resistance, adhesion, and the like, and a well-balanced resin. In order to satisfy these performances, it is necessary to use the specific resin component of the present invention in combination with other components.

In order to form a coating film having high corrosion resistance and high solvent resistance, it is a prerequisite that the coating film is uniformly formed and has excellent adhesiveness, and it is sufficient that the coating film has sufficient resistance. It is important that a mesh structure is formed. For this purpose, it is necessary to use a resin component having a specific chemical structure and a curing agent component together. The base resin molecule is (i) 100
A main skeleton chain having a molecular weight [M _Wi ] of 0 or more, and (ii) a main skeleton chain having one or more side chains bonded to this main skeleton and having a molecular weight of 200 to 5,000. The ratio [M _Wi ] / [M _Wii ] of the molecular weight [M _Wi ] of the above to the total value [M _Wii ] of the molecular weights of the side chains must be 5 or less, and preferably 5 to 0.1 It is preferably 5 to 1. That is, the resin component used in the present invention comprises at least one selected from water-soluble or water-dispersible urethane resins, epoxy resins, polyester resins, and acrylic resins that satisfy the above molecular skeleton requirements. Known resins can be widely used as long as the molecular structure satisfies the above conditions. A coating film formed by using such a resin component can easily form a sufficient network structure, and even in the case of a thin film having a coating film amount of about 0.3 to 6 g / m ² , uniform physical properties can be obtained. Of.

In the present invention, the main skeleton chain is a straight-chain main structure portion having the largest molecular weight when the resin molecule does not form a three-dimensional network structure even when intramolecularly crosslinked, and When the resin forms a three-dimensional network structure by intramolecular crosslinking, it refers to a main structure portion containing a cyclic chain. Further, the side chain refers to a branched chain structure portion which is bonded to the main skeleton chain and branched and extends from this.

The molecular weight of the main skeleton chain of the resin molecule of the resin component contained in the water-based coating composition of the present invention is 1,000 or more, preferably 3,000 to 200,000. If the molecular weight is less than 1,000, the cross-linking efficiency of the resin molecules will be insufficient, and the solvent resistance of the resulting coating film will be insufficient. The molecular weight of the side chain is 200 to 500.
It is in the range of 0, and preferably 200 to 2,000. If the side chain molecular weight is less than 200, the crosslinking density becomes excessively high during the crosslinking of the resin component, and the internal strain increases due to the shrinkage that occurs during curing, so that the resulting coating film is prone to cracking and its corrosion resistance is unsatisfactory. become. On the other hand, when the side chain molecular weight exceeds 5,000, the crosslinking density of the resin component becomes excessively low, and the solvent resistance of the resulting coating film becomes insufficient. Ratio [M _Wi ] / of molecular weight of main skeleton chain [M _Wi ] to total molecular weight of all side chains [M _Wii ] /
[M _Wii ] is 5 or less, preferably 5 to 0.1. If this ratio [M _Wi ] / [M _Wii ] exceeds 5, the cross-linking density of the resin component will be low, and the resulting coating film will have insufficient corrosion resistance.

In the present invention, a coating film having excellent corrosion resistance and solvent resistance can be formed on a metal material by using the resin specified above. It is preferable that each side chain of such a specific resin has at least one selected from an epoxy group, a hydroxyl group, a carboxyl group, and an isocyanate group. Such a side chain is preferably a residue formed by reacting one kind selected from a bisphenol type compound, a polyester compound, a polyacrylic compound and an isocyanate compound with a main skeleton forming compound. By using such a resin, a coating film having more excellent corrosion resistance and solvent resistance can be obtained. The reason for this is that a resin film having a network structure is easily obtained by a crosslinking reaction due to an epoxy group, a hydroxyl group, a carboxyl group or an isocyanate group in the side chain. If the side chain does not have a reactive functional group (epoxy group, isocyanate group, etc.), the crosslinking density will be insufficient, and the resulting coating film will have a low solvent resistance level.

The resin used in the water-based coating composition of the present invention can be self-crosslinked by heating, but since the degree of crosslinking is not sufficient only by heating, the resulting coating film has insufficient corrosion resistance and solvent resistance. It is easy to become. Therefore, in the present invention, the curing agent component is mixed in the coating composition. Examples of the curing agent include epoxy compounds, amines, polyhydric alcohols, polybasic acids, and isocyanate compounds. However, in order to obtain a coating film having more excellent corrosion resistance and solvent resistance, it is preferable to use one or more selected from water-dispersible or water-based epoxy resins and isocyanate compounds as the curing agent. As other curing agents,
Amines, polyhydric alcohols, polybasic acids, etc. are known, but since these have highly hydrophilic functional groups (amino group, hydroxyl group, carboxyl group, etc.), the water resistance of the resulting coating film is high. The sex is insufficient. When an epoxy resin is used as a curing agent, the resulting coating film has excellent chemical resistance and adhesiveness, and the epoxy group at the terminal thereof is highly reactive, which facilitates the crosslinking reaction. Further, the isocyanate compound used as a crosslinking agent, the crosslinking density in the resin molecule is increased by the reaction of the terminal isocyanate group, as a result, the tensile strength of the resulting coating film, solvent resistance, and heat resistance and the like. It is expected to improve.

The compounding amount of the curing agent component is such that the equivalent ratio of the functional group (amino group, carboxyl group, hydroxyl group, etc.) of the resin component to the functional group of the curing agent is 1/10 to 1/1, and the total solid content. The ratio of the solid content weight of the curing agent component to the partial weight is 2 to 3
It is preferably 0%. The functional group equivalent ratio is 1 /
When it is less than 10, or when the ratio of the solid content of the curing agent component to the total weight of solids is less than 2%, the compounding effect of the curing agent component is insufficient and the ratio of functional group equivalents exceeds 1/1. ,
Alternatively, when the ratio of the solid content of the curing agent component to the total solid content weight exceeds 30%, the characteristics of the specific resin component in the coating composition of the present invention cannot be sufficiently exhibited, and one of the resin components cannot be sufficiently exhibited. Since some of the curing agent and the unreacted curing agent remain in the coating film and act as a plasticizer, the resulting coating film has insufficient corrosion resistance and solvent resistance. The functional group of the base resin that reacts with the curing agent may be present in either the main skeleton chain or the side chain, but it is preferable to have a reactive functional group in at least the side chain. The corrosion resistance and solvent resistance of the film are improved.

Total solids weight of the water-based coating composition [a + b +
The ratio of the total solid content weight [a + b] of the component (a) and the component (b) to c] is specified to be 50 to 97%. If it is less than 50%, a desired coating film having high corrosion resistance and high solvent resistance cannot be obtained. Also, if it exceeds 97%, the desired coating film having high corrosion resistance cannot be obtained.

In the present invention, in order to improve the corrosion resistance of the coating film, an inorganic component composed of silica (SiO ₂ ) is added to the total solid weight [a + b].
+ C] is blended in an amount of 3 to 50%. The solid content weight [c] of silica is 3 with respect to the total solid content weight [a + b + c].
%, The effect of improving the corrosion resistance of the obtained coating film is small,
On the other hand, if it exceeds 50%, the binder effect of the resin component on the coating film becomes small, and the corrosion resistance of the resulting coating film decreases. The particle size of silica is 3 to 3
It is preferably 0 nm. If the average particle size is less than 3 nm or more than 30 nm, it may not be possible to obtain a coating film having high corrosion resistance aimed at by the present invention. As the type of silica, liquid phase colloidal silica and vapor phase silica can be used, but the type of silica is not particularly limited in the present invention.

Further, the water-based coating composition of the present invention further contains a lubricating additive, so that the metal material coated with the water-based coating composition, for example, the surface-treated steel material, does not use press oil or the like. Molding process is possible and degreasing process and coating base treatment are unnecessary. Examples of such lubricant additives include inorganic solid lubricants such as graphite and molybdenum disulfide, and organic lubricants such as natural wax and synthetic wax. As a result of examination by the present inventors, the saponification value is 0 or 3
A polyolefin wax having a branched chain structure, which is 0 or less, and preferably has a branched chain structure, is added to the total solid weight [a
+ B + c], it was found to be preferable to contain 1 to 30% by weight. When the saponification value exceeds 30, the resulting wax has an excessive polarity and is likely to be compatible with the resin component, so that it is difficult for the wax to be concentratedly distributed on the resin surface during film formation. It is not appropriate when a processing performance level is required. A more preferable lubricant is a wax having a lower compatibility with a resin component, having no ester bond, and having a saponification value of 0. The blending amount [d] / [a + b + c] of the polyolefin wax is 1
If the amount is less than 10% by weight, the effect of improving the moldability of the coated metal material is small, and if the amount exceeds 30% by weight, the wax is scattered around the press machine during the forming process of the coated metal material. Therefore, it is not preferable in the working environment, and the corrosion resistance of the obtained metal material is lowered. The average particle size of the wax is preferably 0.1 to 7.0 μm. If the average particle size is less than 0.1 μm, the processability of the resulting coating film may be insufficient.
Further, if it exceeds 7.0 μm, the distribution of the solidified wax may become uneven, which is not preferable. As the shape of the wax particles, a spherical shape is more preferable in order to obtain high workability.

The coating composition of the present invention comprises a surfactant called a wettability improver for obtaining a uniform film on the surface to be coated,
It is also possible to contain a thickener, a conductive substance for improving weldability, and a coloring pigment for improving design.

Examples of materials for applying the water-based coating composition of the present invention include cold-rolled steel sheets, zinc-based plated steel sheets, and aluminum-based sheets. Further, it is effective to perform a surface treatment on these metal materials in order to improve their corrosion resistance.
The known chromate treatment or phosphate treatment is suitable for this base treatment. The water-based coating composition of the present invention is applied onto these undercoat films to give a dry coating weight of 0.3 to 6 g / m.
To form a ^second coating, corrosion resistance, it is preferable to form a coating film excellent in performance such as solvent resistance. As a coating method of the coating material, there are a roll coater method, a dipping method, an electrostatic coating method and the like, but the present invention is not particularly limited thereto.

The present invention will be specifically described below with reference to Examples of the present invention together with Comparative Examples. Examples 1 to 20 and Comparative Examples 1 to 13 In each of Examples 1 to 20 and Comparative Examples 1 to 13,
The metal material was painted by the following operations.

1. Preparation of test piece (1-1) Test material The following commercially available materials were used as test materials. (B) Double-sided electrogalvanized steel sheet (EG): thickness = 0.8
mm (Basis weight = 20/20 (g / m ² )) (b) Aluminum plate (A1): 5052 materials,
Plate thickness = 1.0 mm (C) Cold rolled steel plate (SPCC): SPCC material,
Plate thickness = 0.8 mm

(1-2) Degreasing treatment The test material was fine cleaner 4336 (trademark, Nippon Parkerizing Co., Ltd.) which is a silicate alkali degreasing agent.
Manufactured). (Concentration = 20 g / liter, temperature = 60 ° C., spray for 2 minutes) (1-3-1) Underlayer chromate treatment Chromate film formation of EG material is zinc chrome 3367
(Trademark, manufactured by Nihon Parkerizing Co., Ltd.), the chromate film formation on the A1 plate is sprayed with Alchrome 712 (trademark, manufactured by Nihon Parkerizing Co., Ltd.) (bath temperature = 5).
After being washed with water, it was dried at an ambient temperature of 220 ° C. (plate arrival temperature = 100 ° C.) for 10 seconds. The amount of chromium deposited was 50 mg / m ² .

(1-3-2) Zinc Phosphate Treatment Undercoat The zinc phosphate coating is formed by Palbond L3020 (trademark,
Immersion treatment (bath temperature = manufactured by Nihon Parkerizing Co., Ltd.)
45 ° C., time = 2 minutes), washed with water and air dried. The coating weight was 1.9 g / m ² . (1-4) Application of water-based coating composition Test in which the water-based coating composition containing the components shown in Table 1, Table 2, Table 3 and Table 4 in the composition shown in Table 5 was subjected to the above treatment The material was applied with a bar coater, dried at an ambient temperature of 220 ° C. (plate arrival temperature = 140 ° C.) for 30 seconds, and applied. (Amount of coating film = 1.0 g / m ² )

2. Painted plate performance test (2-1) Corrosion resistance A salt spray test according to JIS-Z2371 was performed for 400 hours on the test painted plate to observe the occurrence of white rust. <Evaluation Criteria> ◎ = Rust generation is less than 3% of the total area ○ = Rust generation is 3% or more and less than 10% of the total area △ = Rust generation is 10% or more and less than 30% of the total area × = Rust generation is the entire area More than 30%

(2-2) Alkali resistance The test coated plate was immersed in a silicate-based alkaline degreasing solution (trademark: PALCLEAN 364S, manufactured by Nippon Parkerizing Co., Ltd., concentration = 20 g / liter, temperature = 60 ° C.) for 5 minutes. Then, the corrosion resistance was evaluated. <Evaluation Criteria> ◎ = Rust generation is less than 3% of the total area ○ = Rust generation is 3% or more and less than 10% of the total area △ = Rust generation is 10% or more of the total area and there is no performance degradation × = Rust generation is all Performance deterioration occurs in 10% or more of the area

(2-3) Solvent resistance Gauze is impregnated with methyl ethyl ketone (MEK),
A rubbing test is performed 20 times back and forth on the surface of the organic resin film of the test coated plate, and the surface of the organic resin film is observed. <Evaluation Criteria> ◎ = No change in appearance ○ = Slight film damage is observed △ = Slightly visible base material × = All films are peeled off

(2-4) Workability A blank plate having a diameter of 115 mm was sampled from the test coated plate, and a high-speed cylindrical deep drawing was performed under the conditions of punch diameter = 50 mmφ, wrinkle holding pressure 1 Ton, and deep drawing speed of 30 m / min. The test was conducted. In the test, if necessary, press oil (manufactured by Nippon Kogaku,
# 640) was oiled at ² g / m ² . The aperture ratio at this time was 2.30. <Evaluation Criteria> ◎ = no oil applied, drawing ratio up to 2.40 ○ = no oil applied, drawing ratio down to 2.30 △ = oil applied, drawing ratio down to 2.30 × = With oil, draw ratio = 2.30 No draw through

3. Test Results Table 1 shows the resin component resin molecular structure of the water-based coating composition and Table 2
The type of curing agent for the water-based coating composition is shown in Table 3, the type of silica for the water-based coating composition is shown in Table 3, and the type of wax for the water-based coating composition is shown in Table 4. In addition, Table 5 shows the composition of the water-based coating composition. Furthermore, Table 6 shows the test results of the test materials, the undercoat, the coating composition, and the coated plate of Examples 1 to 20 and Comparative Examples 1 to 13.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

[Table 3]

[0043]

[Table 4]

[0044]

[Table 5]

[0045]

[Table 6]

In Table 6, in Examples 1 to 20, after forming a chromate or phosphate film on a zinc-based plated steel plate, an aluminum plate, and a cold-rolled steel plate, the water-based coating composition of the present invention was applied and dried. To form a film,
The coated plate obtained was good in each of the corrosion resistance, alkali resistance and solvent resistance. Moreover, it was confirmed that good workability can be obtained by adding a lubricant. On the other hand, No. in Table 5 different from the present invention. 18
In Comparative Examples 1 to 13 using the water-based coating composition of
The resulting coated plate was unsatisfactory in corrosion resistance, alkali resistance and solvent resistance.

[0047]

As described above, by applying the water-based coating composition of the present invention to the surface of a metal material such as a galvanized steel sheet, a coated metal material having excellent corrosion resistance, alkali resistance and solvent resistance can be obtained. To be

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C09D 5/00 PPU 5/08 PPX PPY PQA PQE PQH 133/04 PGB 163/00 PHZ PJP 167/02 PKX 175/00 PHW C23C 22/05 // B32B 15/08 G

Claims (5)

[Claims] 1. A resin component comprising (a) at least one selected from a water-soluble or water-dispersible urethane resin, an epoxy resin, a polyester resin, and an acrylic resin, and (b) at least one resin component. And (c) an inorganic component made of silica, and a molecule of each resin of the resin component (a) is (i) 1000.
A main skeleton chain having the above molecular weight, and (ii) one or more side chains bound to this main skeleton chain and having a molecular weight of 200 to 5,000, wherein the molecular weight of the main skeleton chain [M _Wi ] The ratio [M _Wi ] / [M _Wii ] to the total value [M _Wii ] of the side chains is 5
The following is the total solid content weight [a + b] of the resin component (a) and the curing agent component (b) relative to the total solid content weight [a + b + c] of the components (a), (b) and (c). The content [a + b] / [a + b + c] is 50 to 97%, and the total solid content weight of the components (a), (b) and (c) of the solid content weight [c] of the inorganic component (c). [A + b
+ C] content ratio [c] / [a + b + c] is 3 to 5
A water-based coating composition having excellent corrosion resistance and solvent resistance, which is 0%. 2. The water-based paint according to claim 1, wherein each side chain of each resin molecule of the resin component (a) has one selected from an epoxy group, a hydroxyl group, a carboxyl group, and an isocyanate group. Composition. 3. The water-based coating composition according to claim 1, wherein the curing agent component (b) contains at least one selected from water-dispersible or water-soluble polyfunctional epoxy resins and isocyanate compounds. . 4. Silica in the inorganic component (c) is 3 to
The water-based coating composition according to claim 1, which is a fine powder having an average particle diameter of 30 nm. 5. In addition to the components (a), (b) and (c), 1 having a saponification value of 0 or 30 or less.
A total solid content weight of the above-mentioned components (a), (b) and (c), which contains a lubricant component (d) containing one or more polyolefin waxes and has a solid content weight [d] of the lubricant component (d). Content rate to [a + b + c] is 1 to 30%
The water-based coating composition according to claim 1, which is