Anti-corrosion coating method

Abstract

To provide an anticorrosive coating method which can exhibit sufficient anticorrosive property even to a rust surface placed in ultraviolet and frozen environments.SOLUTION: An anticorrosive coating method includes the steps of: coating an aqueous undercoating (I) containing an amino group-containing aqueous resin (A), an antirust agent component (B) and an epoxy group-containing resin emulsion (C) onto a surface of a metal-based base material where rust remains, drying it at normal temperature, and forming an undercoat; and coating an epoxy resin-based top coating (II) containing an epoxy resin component (D) and an amino group-containing resin onto the undercoat, drying it at normal temperature, and forming a topcoat, wherein an epoxy equivalent of the epoxy resin component (D) contained in the epoxy resin-based top coating (II) is 1,700 or less, the epoxy resin-based top coating (II) contains an organic solvent, non-volatile content concentration at the time of coating is 80 mass% or more, and dry film thickness of the formed topcoat is within a range of 0.3 mm to 6 mm.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an anticorrosive coating method using a paint composition.

Background Art

[0002] Steel materials are widely used in various fields such as marine structures, port facilities, ships, buildings, civil engineering structures, and automobiles. However, there is a problem that they corrode when exposed to the natural environment. As a method for preventing or suppressing corrosion, anticorrosive coating is performed.

[0003] Generally, for performing anticorrosive coating on steel structures, pretreatment before coating is important, and the life of the coating film depends on the accuracy thereof. In the pretreatment, removal of the rusted parts of the rusted parts of the steel structure, roughening of the surface of the old coating film, removal of the coating film that has lost the rust prevention effect and has become brittle, etc. are performed. The degree of the pretreatment is called "koren", and it is classified from 1 type of koren to 3 types of koren according to the grade, and the pretreatment is performed by a treatment method according to the grade.

[0004] Although the classification of the grades of koren is not clearly defined, 1 type of koren refers to a full-scale pretreatment that completely removes rust and the coating film and cleans the steel material surface, 3 types of koren is a simple pretreatment that leaves the live film and removes rust and deteriorated coating film, and 2 types of koren is in between.

[0005] And, in order to perform pretreatment up to the 1 type of koren grade that is ideal in the anticorrosive coating of steel structures, it is necessary to perform blasting methods such as sandblasting and shot blasting in which abrasive particles are sprayed with compressed air. However, the blasting method has problems that the mechanical noise, work noise, and the labor and time spent by the painting contractor are large. There has been a need for an anticorrosive coating method that can exhibit long-term anticorrosive properties even with a simple pretreatment of about 2 types of koren or 3 types of koren.

[0006] As such a measure, the applicant of the present application proposed, in Patent Document 1, a repainting method in which rust generated on the surface of an existing structure is simply removed, an inorganic zinc primer is applied thereon, and an epoxy resin-based undercoat paint is applied thereon. Further, in Patent Document 2, an anticorrosive aqueous undercoat paint containing an amino group-containing resin emulsion, an epoxy group-containing resin emulsion, and an anticorrosive pigment component is applied to a metal surface, and then a topcoat paint containing 3 to 25% by mass of glass flakes in the non-volatile content of the paint is applied thereon. An anticorrosive coating method was proposed.

[0007] According to the anticorrosive coating method described in Patent Document 2, it is possible to exhibit sufficient anticorrosive properties even for a rusty surface placed in a severe corrosion environment such as a seashore where the salt content is extremely high and the object to be coated is always placed in a wet state. However, in this anticorrosive coating method, there are cases where sufficient anticorrosive properties cannot be exhibited depending on the situation. For example, when placed under strong ultraviolet rays in summer or in a freezing environment in winter, the expected anticorrosive properties may not be maintained.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] An object of the present invention is to propose an anticorrosive coating method that can exhibit sufficient anticorrosive properties even for a rusty surface placed in an environment accompanied by significant temperature changes.

Means for Solving the Problems

[0010] The inventors of the present invention have intensively studied the above problems. As a result, after applying a specific aqueous epoxy resin paint containing a rust inhibitor and then applying a high-solid paint containing a specific epoxy resin in a thick film, the two are fused to obtain a laminated anticorrosive coating film structure that is resistant to ultraviolet rays and freezing environments even on a rusty surface and can withstand environments with significant temperature changes.

[0011] That is, the present invention Item 1 A step (1) of adjusting an aqueous undercoat paint (I) containing an amino group-containing aqueous resin (A), a rust inhibitor component (B), and an epoxy group-containing resin emulsion (C) by mixing the main component and the curing agent component of a two-component paint; A step (2) of applying the aqueous undercoat paint (I) obtained in step (1) to the surface of a metal-based substrate with remaining rust and drying it at room temperature to form an undercoat film; A step (3) of preparing an epoxy resin-based topcoat paint (II) by mixing the main component containing the epoxy resin component (D) of a two-component paint and the curing agent component containing an amino group-containing resin (E); Applying the epoxy resin-based topcoat paint (II) obtained in step (3) onto the undercoat film and drying it at room temperature An anticorrosive coating method including a step (4) of forming a topcoat film, wherein The epoxy equivalent of the epoxy resin component (D) contained in the epoxy resin-based topcoat paint (II) is 1700 or less, the epoxy resin-based topcoat paint (II) contains an organic solvent, the non-volatile content concentration during coating is 80% by mass or more, and the dry film thickness of the formed topcoat film is Greater than 1 mm and less than or equal to 5 mm within the range of, an anticorrosive coating method. Item 2 The anticorrosive coating method according to item 1, wherein the aqueous undercoat paint (I) is a two-component paint obtained by mixing a main component containing an amino group-containing aqueous resin (A) and a rust inhibitor component (B) and a curing agent component containing an epoxy group-containing resin emulsion (C). Item 3 The anticorrosive coating method according to item 2, wherein the amino group-containing aqueous resin (A) is an amino group-containing resin emulsion (a) having a primary amino group using an epoxy resin (a1), a polyamine compound (a2), and a ketone compound (a3) as production raw materials. Item 4 The anticorrosive coating method according to any one of Items 1 to 3, wherein the aqueous undercoat paint (I) further contains at least one selected from fibrous inorganic compounds, polycarbodiimide compounds, and softeners. Item 5 The anticorrosive coating method according to any one of Items 1 to 4, wherein the epoxy resin component (D) contains bisphenol A type epoxy resin and / or bisphenol F type epoxy resin. Item 6 The anticorrosive coating method according to any one of Items 1 to 5, wherein the epoxy resin-based topcoat paint (II) contains a pigment content. Item 7 The anticorrosive coating method according to any one of Items 1 to 6, wherein the epoxy resin-based topcoat paint (II) contains a rust preventive agent component. Item 8 The anticorrosive coating method according to any one of Items 1 to 7, wherein the epoxy resin-based topcoat paint (II) contains a fibrous inorganic compound and / or glass flake. relates to.

Advantages of the Invention

[0012] According to the anticorrosive coating method of the present invention, excellent anticorrosive properties can be exhibited even when applied to a rusty surface placed in a strong ultraviolet ray or freezing environment, and the object to be coated can be protected over a long period of time.

Embodiments for Carrying Out the Invention

[0013] <Object to be Coated> The surface of the metal-based substrate to which the method of the present invention is applied includes metal materials such as steel, but is also applicable to non-ferrous metals such as zinc and aluminum.

[0014] Specific examples of the object to be coated to which the method of the present invention is applied include structures having the metal-based substrate with remaining rust as a constituent member, processed products processed into plates, rods, tubes, etc. For example, civil engineering structures such as towers, bridges, and tanks; structures of various plants such as oil and gas drilling plants and power plants; architectural structures such as houses and buildings; outdoor appliances such as guard fences and industrial machines. In the present invention, the effect can be maximally exerted particularly when a harbor or marine structure is used as the object to be coated. The harbor or marine structure is a structure in which a support member supports an upper structure built on the sea or in a harbor. Specifically, it includes a pier, a dolphin, a revetment, a breakwater, a quay wall, an artificial island, a submerged tunnel, an offshore airport, an offshore oil facility, an offshore gas facility, an offshore wind power plant, etc.

[0015] The aqueous undercoat paint (I) used in the anticorrosive coating method of the present invention contains an amino group-containing aqueous resin (A), a rust inhibitor component (B), and an epoxy group-containing resin emulsion (C).

[0016] <Amino group-containing aqueous resin (A)>; In the present invention, examples of the amino group-containing aqueous resin (A) include water-soluble or emulsion-type resins containing two or more primary or secondary amino groups in one molecule.

[0017] Specifically, polyamine compounds such as aliphatic polyamines, alicyclic polyamines, aromatic polyamines, and heterocyclic polyamines; modified products of these polyamine compounds; for example, fatty acid-modified products such as polyamideamines, epoxy adducts, Mannich-modified products (e.g., phenalkamine, phenalkamide), Michael adducts, ketimines, aldimines; etc. Resins obtained by solubilizing or emulsifying them are included.

[0018] From the viewpoint of anticorrosion, the amino group-containing aqueous resin (A) contained in the aqueous undercoat paint (I) is preferably an amino group-containing resin emulsion (a) having a primary amino group described below.

[0019] Examples of the amino group-containing resin emulsion (a) having the primary amino group include resins produced from an epoxy resin (a1), a polyamine compound (a2), and a ketone compound (a3) as production raw materials.

[0020] 《Epoxy resin (a1)》 The epoxy resin (a1) as a production raw material of the amino group-containing resin emulsion (a) is a resin having at least 1, preferably 2 or more epoxy groups in the molecule, and those having an epoxy equivalent within the range of 450 to 3000 g / eq are suitable. The epoxy equivalent is the number of grams (g / eq) of the resin containing 1 gram equivalent of epoxy groups, and in this specification, the epoxy equivalent published by the manufacturer or measured according to JIS K 7236 is used.

[0021] Specific examples of the epoxy resin (a1) include bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol AD type epoxy resin; epoxy ester resins obtained by modifying the above bisphenol type epoxy resins with dibasic acids, etc.; novolak type epoxy resins such as cresol novolak type epoxy resin and phenol novolak type epoxy resin; alicyclic epoxy resins; polyglycol type epoxy resins; hydrogenated bisphenol A type epoxy resin; aliphatic type epoxy resins such as ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane polyglycidyl ether, hexahydrophthalic acid diglycidyl ester, glycerin polyglycidyl ether, diglycerin polyglycidyl ether, and polyglycerin polyglycidyl ether; and epoxy group-containing acrylic resins containing an epoxy group-containing acrylic monomer such as glycidyl (meth)acrylate as a constituent component. These can be used alone or in combination of two or more.

[0022] The epoxy resin (a1) also includes an epoxy resin obtained by reacting the above-exemplified epoxy resin with difunctional polyester polyols, difunctional polyether polyols, bisphenols, dibasic carboxylic acids, etc. so that the epoxy groups are in excess.

[0023] 《Polyamine compound (a2)》 As the polyamine compound (a2) constituting the amino group-containing resin emulsion (a), a polyamine compound having primary amino groups at both molecular ends and at least one secondary amino group is preferable.

[0024] Examples of such polyamine compounds (a2) include dialkylene triamines such as dimethylene triamine, diethylene triamine, dipropylene triamine, dibutylene triamine, and bis(hexamethylene)triamine; trialkylene tetramines such as triethylene tetramine and tripropylene tetramine; tetraalkylene pentamines such as tetraethylene pentamine and tetrapropyl pentamine; pentaalkylene hexamine; hexaalkylene heptamine; and the like. These can be used alone or in combination of two or more.

[0025] Particularly in the present invention, from the viewpoints of the storage stability of the aqueous undercoat paint (I) and the corrosion resistance against a metal substrate having rust, it is preferable that the polyamine compound (a2) is a dialkylene triamine, and a dialkylene triamine having an alkylene group with 2 to 8 carbon atoms, preferably 3 to 6 carbon atoms, is particularly suitable.

[0026] 《Ketone compound (a3)》 Examples of the ketone compound (a3) include methyl isopropyl ketone, diisobutyl ketone, methyl isobutyl ketone, diethyl ketone, ethyl butyl ketone, ethyl propyl ketone, dipropyl ketone, and methyl ethyl ketone. These can be used alone or in combination of two or more.

[0027] Examples of the method for producing the amino group-containing resin emulsion (a) include a production method in which the primary amino group of the polyamine compound (a2) is reacted with a ketone compound (a3) for ketimine formation, then the secondary amino group is reacted with the epoxy group of the epoxy resin (a1), and then the ketimine is returned to the primary amino group by hydrolysis during water dilution.

[0028] According to the above production method, the amino group-containing resin emulsion (A) can have a primary amino group, which is a water-dispersible group, at the resin terminal in the presence of water, and is useful for forming a corrosion-resistant coating film having excellent corrosion resistance even when the metal surface has a rusty surface.

[0029] The amino group-containing resin emulsion (a) may be a resin using a reactive group-containing softening agent as a production raw material in addition to the epoxy resin (a1), the polyamine compound (a2), and the ketone compound (a3). This is effective in improving the adhesion of the laminated coating film formed by the corrosion-resistant coating method of the present invention to the rusty surface.

[0030] Examples of the reactive group-containing softening agent include compounds having functional groups such as carboxyl groups and / or glycidyl groups. Specific examples thereof include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane polyglycidyl ether, hexahydrophthalic acid diglycidyl ester, glycerin polyglycidyl ether, diglycerin polyglycidyl ether, polyglycerin polyglycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, benzyl glycidyl ether, cresyl glycidyl ether, tert-butylphenyl glycidyl ether and other alkyl glycidyl ether compounds; Alkyl glycidyl ester compounds such as glycidyl butyrate, glycidyl stearate, glycidyl neodecanoate, epoxidized soybean oil, epoxybutyl stearate, di-2-ethylhexyl epoxyhexahydrophthalate, diisodecyl epoxyhexahydrophthalate, epoxytriglyceride, octyl epoxidized oleate, decyl epoxidized oleate, etc.; Long-chain alkyl fatty acids such as coconut oil fatty acid, cottonseed oil fatty acid, linseed oil fatty acid, rice bran oil fatty acid, fish oil fatty acid, tall oil fatty acid, soybean oil fatty acid, linseed oil fatty acid, tung oil fatty acid, rapeseed oil fatty acid, castor oil fatty acid, dehydrated castor oil fatty acid, safflower oil fatty acid, etc.; etc can be mentioned.

[0031] The above amino group-containing resin emulsion (a) is well dispersed in the aqueous medium due to the presence of amino groups which may be neutralized. The average particle size in the case of an aqueous dispersion is in the range of 50 to 500 nm, particularly 100 to 300 nm.

[0032] Examples of the neutralizing agent used for neutralization include organic acids such as formic acid, acetic acid, oxalic acid, malonic acid, succinic acid, malic acid, citric acid, glutaric acid, adipic acid, maleic acid, lactic acid, propionic acid, hydroxyethanediphosphonic acid, methanesulfonic acid, etc.; inorganic acids such as hydrochloric acid, phosphoric acid, sulfuric acid, zirconium hydrofluoric acid, silicon hydrofluoric acid, nitric acid, etc.; and other acid compounds.

[0033] The total amine value of the resin of the above amino group-containing resin emulsion (a) is in the range of 20 to 120 mgKOH / g, preferably 40 to 100 mgKOH / g.

[0034] Also, the weight average molecular weight of the resin of the amino group-containing resin emulsion (a) is preferably in the range of 1000 to 20000, preferably 2000 to 8000.

[0035] In this specification, the average particle diameter of the resin emulsion is the value of the volume average particle diameter measured by the Coulter counter method at a measurement temperature of 20°C. The measurement by the Coulter counter method can be performed, for example, using "COULTER N4 type" (trade name, manufactured by Beckman Coulter, Inc.).

[0036] In this specification, the amine value is the amount (mg) of potassium hydroxide equivalent to hydrochloric acid required to neutralize the amine contained in 1 g of the sample, and in this specification, the amine value published by the manufacturer or measured according to JIS K 7237 is used.

[0037] The weight average molecular weight is a value obtained by converting the retention time (retention volume) measured using gel permeation chromatography (GPC) into the molecular weight of polystyrene based on the retention time (retention volume) of a standard polystyrene with a known molecular weight measured under the same conditions. Four columns, namely, "TSKgel G-4000H×L", "TSKgel G-3000H×L", "TSKgel G-2500H×L", and "TSKgel G-2000H×L" (all trade names, manufactured by Tosoh Corporation) were used, and the measurement was carried out under the conditions of mobile phase: tetrahydrofuran, measurement temperature: 40°C, flow rate: 1 ml / min, and detector: RI.

[0038] When the amino group-containing aqueous resin (A) is an amino group-containing resin emulsion (a), the non-volatile content of the emulsion (a) is suitably in the range of 15 to 50% by mass in the non-volatile content of the aqueous undercoat paint (I).

[0039] In this specification, the non-volatile content means the residue obtained by removing the volatile components, and the residue may be in a solid state or a liquid state at normal temperature. For example, it refers to the residual components when the sample is treated at 105°C for 3 hours to remove the volatile components.

[0040] <Rust inhibitor component (B)> In the present invention, as the rust inhibitor component (B), a rust inhibitor component known in the paint field can be used, which may be an inorganic compound or an organic compound, and there is no limitation on its form such as a single compound, a composite compound, or a composition in which a plurality of these compounds are used in combination. Specifically, phosphate-based metal compounds such as zinc phosphate, magnesium phosphate, magnesium ammonium phosphate eutectic, magnesium hydrogen phosphate, magnesium dihydrogen phosphate, magnesium calcium phosphate eutectic, magnesium cobalt phosphate eutectic, magnesium nickel phosphate eutectic, calcium phosphate, calcium ammonium phosphate, calcium hydrogen phosphate, calcium dihydrogen phosphate, calcium fluoride phosphate, aluminum phosphate, aluminum hydrogen phosphate; Phosphite-based metal compounds such as magnesium phosphite, calcium phosphite, magnesium calcium phosphite eutectic, basic zinc phosphite, barium phosphite, manganese phosphite, calcium hypophosphite; Metal silicate salts such as calcium silicate, zinc silicate, aluminum silicate, aluminum orthosilicate, hydrated aluminum silicate, aluminosilicate, borosilicate, beryllosilicate, calcium aluminum silicate, sodium aluminum silicate, beryllium aluminum silicate, sodium silicate, calcium orthosilicate, calcium metasilicate, sodium calcium silicate, zirconium silicate, magnesium orthosilicate, magnesium metasilicate, manganese silicate, barium silicate; Metal ion exchange silica-based compounds such as magnesium ion exchange silica, calcium ion exchange silica; Condensed phosphate-based metal compounds such as aluminum dihydrogen tripolyphosphate, magnesium oxide composite of aluminum dihydrogen tripolyphosphate, aluminum tripolyphosphate, zinc oxide composite of aluminum dihydrogen tripolyphosphate; Vanadium-based metal compounds such as vanadium pentoxide, calcium vanadate, magnesium vanadate and ammonium metavanadate, fired product of manganese oxide and vanadium oxide, fired product of calcium phosphate and vanadium oxide; Molybdic acid-based metal compounds such as aluminum molybdate, calcium molybdate, and aluminum phosphomolybdate; Zinc-based compounds such as zinc and zinc oxide; Silica-based compounds such as silica and colloidal silica; Composite metal oxides such as composite oxides of iron oxide and magnesium oxide, composite oxides of iron oxide and calcium oxide, and composite oxides of iron oxide and zinc oxide; Sulfur-containing organic compounds such as triazole compounds, thiol compounds, thiadiazole compounds, and thiazole compounds; Hydroxides or oxides of alkaline earth metals such as calcium hydroxide, calcium oxide, strontium hydroxide, strontium oxide, barium oxide, and barium hydroxide, and metal sulfates such as magnesium sulfate, aluminum sulfate, nickel sulfate, iron sulfate, cobalt sulfate, copper sulfate, zinc sulfate, tin sulfate, and chromium sulfate; may be mentioned. As described above, these may be used alone or in combination of two or more, or may be a composite of two or more. Further, modified or treated products of these exemplified compounds with silicate compounds such as silica and calcium silicate or magnesium oxide are also included in the rust inhibitor component (B).

[0041] The rust preventive agent component (B) may be a commercially available product used alone or in combination of a plurality thereof. Examples of such commercially available products include "EXPERT NP-1000", "EXPERT NP-1020C", "EXPERT NP-1100", "EXPERT NP-1102" (all manufactured by Toho Pigment Co., Ltd., trade names), "LF Bousei CP-Z", "LF Bousei MZP-500", "LF Bousei CRFC-1", "LF Bousei M-PSN", "LF Bousei MC-400WR", "LF Bousei PM-300", "LF Bousei PM-308" (all manufactured by Kikuchi Color Co., Ltd., trade names), "K-WHITE140", "K-WHITE Ca650", "K-WHITE450H", "K-WHITE G-105", "K-WHITE #105", "K-WHITE #82" (all manufactured by Teika Co., Ltd., trade names), "SHIELDEX C303", "SHIELDEX AC-3", "SHIELDEXC-5" (all manufactured by W.R. Grace & Co.), "Silomask 52", "Silomask 52M", "Silomask 22MR-H" (all manufactured by Fuji Silysia Co., Ltd.), "Nobinox ACE-110" (manufactured by SNCZ, France), and the like.

[0042] The blending amount of the rust preventive agent component (B) is suitably in the range of 5 to 90 parts by mass, more preferably 10 to 80 parts by mass, based on 100 parts by mass of the non-volatile content of the aqueous undercoat paint (I).

[0043] <Epoxy group-containing resin emulsion (C)> In the present invention, the raw materials for producing the epoxy group-containing resin emulsion (C) are not particularly limited, and the epoxy group-containing compounds listed in the description of the epoxy resin (a1) above can be exemplified.

[0044] The above epoxy group-containing resin emulsion (C) is obtained by dispersing the epoxy group-containing compound with a dispersion stabilizer or surfactant having an anionic, nonionic or cationic hydrophilic group. In the aqueous undercoat paint (I), when the amino group-containing aqueous resin (A) is an amino group-containing resin emulsion (a) having a primary amino group, from the viewpoint of obtaining a coating film having a large number of epoxy groups capable of reacting with the amino group and excellent curability, it is preferable that the epoxy group-containing resin emulsion (C) contains a novolak type epoxy resin as a part of its components.

[0045] Also, the epoxy equivalent of the epoxy resin emulsion (C) is preferably lower than that of the epoxy resin (a1) in the amino group-containing resin emulsion (a) from the viewpoint of the film-forming property of the undercoat film formed by the aqueous undercoat paint (I). Specifically, it is preferable that the epoxy equivalent is at least 50 g / eq, preferably in the range of 100 to 500 g / eq.

[0046] When the average particle diameter of the above epoxy group-containing resin emulsion (C) is dispersed in an aqueous medium, it is preferably in the range of 50 to 1500 nm, preferably 200 to 1000 nm.

[0047] <Aqueous undercoat paint (I)> The above aqueous undercoat paint (I) used in the anticorrosive coating method of the present invention is a two-component paint composition obtained by mixing a main component and a curing agent component. As the paint form, if the amino group-containing aqueous resin (A) and the epoxy group-containing resin emulsion (C) are separated during storage, the rust preventive agent component (B) can be included in either or both of the main component and the curing agent component. In the present invention, the aqueous undercoat paint (I) is provided as a two-component paint composition comprising a main component containing an amino group-containing aqueous resin (A) and a rust preventive agent component (B), and a curing agent component containing an epoxy group-containing resin emulsion (C). It is desirable that the coating operator mixes the main component, the curing agent component and, if necessary, a diluent, etc. at the site for preparation.

[0048] In the present invention, since the main component contains the rust inhibitor component (B) together with the amino group-containing aqueous resin (A), even when the amount of the rust inhibitor component (B) is large, the production and storage stability of the main component can be good, and the coating film formed from the aqueous undercoat paint (I) can exhibit stable corrosion resistance against a rusty surface.

[0049] In the above-mentioned aqueous undercoat paint (I), ordinary paint additives such as fibrous inorganic compounds, polycarbodiimide compounds, softeners, coloring pigments, extender pigments, pigment dispersants, organic solvents, surface modifiers, defoamers, thickeners, curing catalysts, surfactants, anti-settling agents, plasticizers, reactive diluents, anti-freezing agents, anti-skinning agents, pH adjusters, and preservatives can be included.

[0050] Examples of these fibrous inorganic compounds include glass fiber, silicon carbide, silicon nitride, wollastonite, sepiolite, chrysotile, amosite, tremolite, zeolite, calcium metasilicate, zonolite, potassium titanate, rock wool, aluminum silicate, carbon fiber, aramid fiber, aluminum borate, acicular calcium carbonate, acicular basic magnesium sulfate, acicular zinc oxide, aragonite-type light calcium carbonate, spindle-type light calcium carbonate, satin white, etc. These can be used alone or in combination of two or more.

[0051] The aspect ratio of the fibrous inorganic compound is preferably 3.5 or more, preferably in the range of 4 to 30. The aspect ratio is the value of the major axis diameter / minor axis diameter. Here, the minor axis diameter and major axis diameter referred to are the minor axis diameter and major axis diameter of each of 100 primary particles existing within a certain area by electron microscope observation, and the respective number average values are obtained.

[0052] Also, the average fiber length of the fibrous inorganic compound is preferably in the range of 5 to 300 μm, particularly 10 to 200 μm. In this specification, the average fiber length is the average value of the major axis diameters obtained in the measurement of the aspect ratio.

[0053] Examples of the softening agent include organic compounds that are liquid at normal temperature and have a weight-average molecular weight equal to or less than that of the resin of the epoxy group-containing resin emulsion. Specifically, glycol ether compounds, alkyl ester compounds, epoxy compounds, etc. can be mentioned.

[0054] Examples of the glycol ether compound include diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, ethylene glycol monophenyl ether, diethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol monobutyl ether, propylene glycol monophenyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether, 2-ethylhexyl glycol, etc.

[0055] Examples of the alkyl ester compound include dibutyl adipate, DBE (dibasic acid ester), dibutyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, diisodecyl phthalate, diheptyl phthalate, di-n-octyl phthalate, butyl benzyl phthalate, ethyl phthalyl ethyl glycolate, di-2-ethylhexyl adipate, dibutyl diglycol adipate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, 2,2,4-trimethyl-1,3-pentanediol 2-ethylhexanoate isobutyrate, 2,2,4-trimethyl-1,3-pentanediol di-2-ethylhexanoate, etc.

[0056] Examples of the epoxy compound include alkyl glycidyl ether compounds such as ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6 - hexanediol diglycidyl ether, trimethylolpropane polyglycidyl ether, hexahydrophthalic acid diglycidyl ester, glycerin polyglycidyl ether, diglycerin polyglycidyl ether, polyglycerin polyglycidyl ether, butyl glycidyl ether, 2 - ethylhexyl glycidyl ether, phenyl glycidyl ether, benzyl glycidyl ether, cresyl glycidyl ether, tert - butylphenyl glycidyl ether; alkyl glycidyl ester compounds such as glycidyl butyrate, glycidyl stearate, glycidyl neodecanoate, epoxidized soybean oil, epoxy butyl stearate, di - 2 - ethylhexyl epoxyhexahydrophthalate, diisodecyl epoxyhexahydrophthalate, epoxy triglyceride, octyl epoxidized oleate, decyl epoxidized oleate, etc. The above - mentioned compounds can be used alone or in combination of two or more.

[0057] <Coating of the aqueous undercoat paint (I)> For the coating of the above - mentioned aqueous undercoat paint (I), conventionally known methods such as air spray, airless spray, brush coating, roller coating, etc. can be adopted. As the drying method, room - temperature drying is preferred, but forced drying or heat drying can be used in combination as necessary.

[0058] In the anticorrosive coating method of the present invention, the dry film thickness of the undercoat film formed by the aqueous undercoat paint (I) is preferably in the range of 10 - 200 μm, more preferably 30 - 150 μm.

[0059] In this specification, the dry film thickness is obtained by theoretically calculating from the coating amount.

[0060] In the method of the present invention, the epoxy resin-based topcoat paint (II) applied on the undercoat film formed by the aqueous undercoat paint (I) contains an epoxy resin component (D) and an amino group-containing resin component (E).

[0061] <Epoxy resin component (D)> In the anticorrosive coating method of the present invention, the epoxy resin-based topcoat paint (II) applied on the undercoat film formed by the aqueous undercoat paint (I) contains an epoxy resin component (D).

[0062] In the present invention, the epoxy equivalent of the epoxy resin component (D) is preferably 1700 g / eq or less, and more preferably in the range of 100 to 800 g / eq, particularly 150 to 500 g / eq. When the epoxy equivalent of the epoxy resin component (D) contained in the epoxy resin-based topcoat paint (II) is within the above range, the laminated coating film formed by the anticorrosive coating method of the present invention is excellent in rust surface corrosion resistance under ultraviolet rays and / or a freezing atmosphere, and has the effect of withstanding an environment accompanied by significant temperature changes.

[0063] The epoxy resin component (D) is preferably dilutable with an organic solvent. Specific examples thereof include the same compounds as those listed in the description of the above epoxy resin (a1). In particular, it is preferable to use a combination of an organic solvent-dilutable bisphenol A type epoxy resin and a bisphenol F type epoxy resin.

[0064] The content of the epoxy resin component (D) is preferably 15% by mass or more, particularly in the range of 20 to 80% by mass in the non-volatile matter of the epoxy resin-based topcoat paint (II).

[0065] In the epoxy resin-based topcoat paint (II), when the epoxy resin contained in the main component is a combination of a bisphenol A type epoxy resin and a bisphenol F type epoxy resin, the mixing ratio thereof is preferably in the range of 5 / 95 to 95 / 5, particularly 10 / 90 to 90 / 10 in terms of the mass ratio of bisphenol A type epoxy resin / bisphenol F type epoxy resin from the viewpoints of adhesion to the rust surface and thick film finishability.

[0066] <Amino group-containing resin (E)> On the other hand, examples of the amino group-containing resin (E) contained in the curing agent component of the epoxy resin-based topcoat paint (II) include organic solvent-based resins containing two or more amino groups in one molecule. Specifically, polyamine compounds such as aliphatic polyamines, alicyclic polyamines, aromatic polyamines, and heterocyclic polyamines; modified products of these polyamine compounds; for example, fatty acid modified products such as polyamide amines, epoxy adducts, Mannich modified products (e.g., phenalkamine, phenalkamide), Michael adducts, ketimines, aldimines, etc. These may be used alone or as commercially available products in a combination of plural.

[0067] From the viewpoints of thick film finishability and corrosion resistance against rusty surfaces, it is preferable to use a resin in which the amine value is in the range of 50 to 500 mgKOH / g, particularly 150 to 400 mgKOH / g, as the amino group-containing resin (E).

[0068] <Organic solvent> The epoxy resin-based topcoat paint (II) contains an organic solvent from the viewpoint of thick film coating workability. As the organic solvent, organic solvents known in the paint field can be used, but it is preferable to use at least one organic solvent selected from the group consisting of hydrocarbon-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, glycol-based organic solvents, and ketone-based organic solvents. Examples of the hydrocarbon-based organic solvent include mineral spirit, solvent naphtha, terpene, normal decane, toluene, xylene, etc.

[0069] Examples of the alcohol-based organic solvent include methanol, ethanol, isopropanol, tert-butanol, secondary butanol, isobutanol, n-butanol, methyl isobutyl carbinol, etc. Examples of the ester-based organic solvent include ethyl acetate, butyl acetate, isobutyl acetate, etc. Examples of glycol-based organic solvents include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monotert-butyl ether, and the like. Examples of ketone-based organic solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl isoamyl ketone, diisobutyl ketone, and the like. These can be used alone or in combination of two or more.

[0070] The content of the organic solvent is adjusted by the organic solvent itself or the carry-in from raw materials so that the non-volatile content concentration of the epoxy resin-based topcoat paint (II) during coating is within the range described below.

[0071] <Pigment content> In the present invention, the epoxy resin-based topcoat paint (II) preferably contains a pigment content. As the pigment content, coloring pigments, extender pigments, and the like are preferably used.

[0072] Examples of coloring pigments include titanium white, red iron oxide, carbon black, iron black, zinc white, and the like. Examples of extender pigments include calcium carbonate, barium sulfate, barium carbonate, magnesium silicate, clay, talc, calcined kaolin, and the like.

[0073] The content of the pigment content is preferably in the range of 0.1 to 50% by mass, more preferably 2 to 40% by mass, in the non-volatile content of the epoxy resin-based topcoat paint (II).

[0074] <Rust inhibitor component> Further, in the present invention, from the viewpoint of rust surface corrosion protection under ultraviolet rays and / or a freezing atmosphere, the epoxy resin-based topcoat paint (II) preferably contains a rust inhibitor component as a part of its components. Examples of the rust inhibitor component include the same compounds as the above rust inhibitor component (B). The content of the rust inhibitor component when the rust inhibitor component is included is preferably in the range of 0.1 to 30% by mass, more preferably 1.5 to 20% by mass, in the non-volatile content of the epoxy resin-based topcoat paint (II).

[0075] <Fibrous inorganic compound and / or glass flake> In addition, from the viewpoint of adhesion to the rust surface in the case of a thick film, the epoxy resin-based topcoat paint (II) may contain a fibrous inorganic compound and / or glass flake. Examples of the fibrous inorganic compound include the compounds exemplified in the description of the aqueous undercoat paint (I). The glass flake refers to flat glass, and it is preferable to use those having an average particle diameter of 10 to 300 μm.

[0076] In this specification, the average particle diameter of the glass flake is the median diameter derived from the volume distribution measured by the laser diffraction scattering method.

[0077] As the glass flake, commercially available ones can be used. Specifically, for example, "RCF-15", "RCF-140", "RCF-160", "RCF-600", "REF-600", "RCF-2300" (all of the above are manufactured by Nippon Sheet Glass Co., Ltd.) and the like can be mentioned. When using a fibrous inorganic compound and glass flake, the content is suitably in the range of 0.1 to 30% by mass, preferably 1.5 to 20% by mass, in the non-volatile content of the aqueous undercoat paint (I).

[0078] <Epoxy resin-based topcoat paint (II)> The above epoxy resin-based topcoat paint (II) is provided as a two-component paint composition comprising a main component containing an epoxy resin component (D) and a curing agent component containing an amino group-containing resin component (E), and is a paint that a painter mixes the main component, the curing agent component and a diluent as necessary at the site for preparation.

[0079] In the present invention, from the viewpoint of the finish property on the rust surface, the non-volatile content concentration at the time of applying the epoxy resin-based topcoat paint (II) is 80% by mass or more, preferably 90% by mass or more. In addition, the epoxy resin-based topcoat paint (II) can contain, as main ingredient(s) or curing agent ingredient(s) or both, resin components for modification such as resins other than the above epoxy resin component (D); paint additives such as pigment dispersants, surface conditioners, defoamers, thickeners, curing catalysts, plasticizers, reactive diluents, antifreeze agents, anti-skinning agents, and preservatives.

[0080] It is preferable that both the main ingredient and the curing agent ingredient in the epoxy resin-based topcoat paint (II) contain pigment content. By both the main ingredient and the curing agent ingredient containing pigment content, a coating film with a film thickness described later can be obtained. In this case, the proportion of the pigment content contained in the main ingredient is 0.1 to 50% by mass, particularly about 2 to 30% by mass in the non-volatile content of the main ingredient, and the proportion of the pigment content contained in the non-volatile content of the curing agent ingredient is appropriately in the range of 1 to 70% by mass, particularly 10 to 60% by mass.

[0081] <Coating of Epoxy Resin-Based Topcoat Paint (II)> In the present invention, from the viewpoints of rust surface corrosion prevention and adhesion to rust surfaces under ultraviolet rays and / or in a freezing atmosphere, the dry film thickness of the topcoat film formed by the epoxy resin-based topcoat paint (II) is in the range of 0.3 mm to 6 mm, and preferably in the range of 1 mm to 5 mm.

[0082] There is no limitation on the coating method, and conventionally known methods such as airless spraying, brush coating, spatula coating, brush painting, and roller coating can be adopted. Also, it may be coated in two or more times until the target film thickness is reached, but it is also possible to coat in one time. As the drying method, normal temperature drying is preferable, but forced drying or heat drying may be used in combination as necessary. Further, another topcoat paint may be applied on top of the topcoat film formed by the epoxy resin-based topcoat paint (II) as necessary.

Examples

[0083] Hereinafter, the present invention will be further described with reference to examples. Here, 'parts' and '%' respectively mean'mass parts' and'mass %'.

[0084] Production Example 1 <Production of Aqueous Undercoat Paint> Production Example 1 Into a container, 222 parts (100 parts of non-volatile content) of an amino group-containing resin emulsion (a) (Note 1), 10 parts of a rust preventive pigment (B-1) (Note 3), 10 parts of a rust preventive pigment (B-2) (Note 4), 20 parts of a rust preventive pigment (B-3) (Note 5), 3 parts of calcium silicate, 10 parts of glass fiber, 8 parts of a pigment dispersant, 20 parts of ethylene glycol monobutyl ether, 40 parts of titanium oxide, and 60 parts of talc were blended and stirred and mixed to obtain a main component. Into another container, 35.2 parts (17.6 parts of non-volatile content) of an epoxy group-containing resin emulsion (C-2) (Note 9), 5 parts of 1,6-hexanediol diglycidyl ether, and 7.5 parts (3 parts of non-volatile content) of a polycarbodiimide emulsion were added, stirred and mixed to obtain a curing agent component, which was added to the above main component to obtain an aqueous undercoat paint (I-1).

[0085] Production Examples 2 to 9 In the above Production Example 1, aqueous undercoat paints (I-2) to (I-9) were produced in the same manner as in Production Example 1 except that the blending composition was as shown in Table 1 below. The numerical values in Table 1 are the non-volatile content mass.

[0086]

Table 1

[0087] (Note 1) Amino group-containing resin emulsion (a): Into a flask equipped with a stirrer, thermometer, nitrogen inlet tube, and reflux condenser, 3200 parts of "jER828" (trade name, manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin, epoxy equivalent 190, number average molecular weight 375), 1700 parts of bisphenol A (molecular weight 228), 900 parts of methyl isobutyl ketone (boiling point 120°C), and 5.0 parts of benzyldimethylamine were charged and reacted at 120°C until the epoxy equivalent per non-volatile content reached 2500 g / equivalent.

[0088] Next, 590 parts of the ketimine compound of dipropylenetriamine with methyl isobutyl ketone were added and reacted at 120 °C for 1 hour. Then, 54 parts of deionized water and 380 parts of glycidyl neodecanoate were charged and reacted at 100 °C for 2 hours. Then, 90 parts of acetic acid and 70 parts of deionized water were added to stir and mix the internal liquid. After adding 6500 parts of deionized water for water dispersion, the pressure was reduced to remove methyl isobutyl ketone, and the solid content was adjusted with deionized water to obtain an amino group-containing resin emulsion (a) that was milky white and had a non-volatile content of 45% and a primary amino group at the resin terminal. The emulsion (a) had a weight-average molecular weight of 7000 for the resin before neutralization, an average particle size of 250 nm, and an amine value of 60 mgKOH / g per non-volatile content. (Note 2) Epoxy group-containing resin emulsion (C-1): Nonionic bisphenol A type epoxy resin emulsion, non-volatile content 50%, epoxy equivalent per non-volatile content 535 (Note 3) Rust preventive pigment (B-1): "K-WHITE G-105", manufactured by Teika Co., trade name, magnesium oxide composite of aluminum dihydrogen tripolyphosphate, magnesium oxide modification amount 15% (Note 4) Rust preventive pigment (B-2): "LF Bousei MZP-500", trade name, manufactured by Kikuchi Color Co., magnesium phosphate (Note 5) Rust preventive pigment (B-3): "Silomask 22MR-H", manufactured by Fuji Silysia Chemical Ltd., trade name, magnesium ion-exchanged silica (Note 6) Triazole group-containing resin: In a flask equipped with a stirrer, thermometer, nitrogen inlet tube, and reflux condenser, 190 parts of "jER828" (trade name, bisphenol A type resin manufactured by Mitsubishi Chemical Co., epoxy equivalent 190, number-average molecular weight 375), 84 parts of 3-amino-1,2,4-triazole, and methyl isobutyl ketone were charged and reacted for 2 hours while heating to 110 °C to produce a triazole group-containing resin solution. The non-volatile content is 80%, and the non-volatile amine value is 205 mgKOH / g. (Note 7) Glass fiber: Aspect ratio 20, average fiber length 80 μm (Note 8) Pigment dispersant: Polyethylene glycol-polypropylene glycol-modified styrene maleic acid copolymer, acid value 10 mgKOH / g (Note 9) Epoxy resin emulsion (C-2): Nonionic phenol novolak type epoxy resin emulsion, nonvolatile content 50%, epoxy equivalent per nonvolatile content 200, weight average molecular weight 1200, average particle size 550 nm, (Note 10) Amino group-containing resin emulsion A, aqueous modified alicyclic polyamine, nonvolatile content 50%, active hydrogen equivalent per nonvolatile content 196 (Note 11) Polycarbodiimide emulsion: Nonvolatile content 40%, carbodiimide equivalent 365.

[0089] <Manufacture of Epoxy Resin-based Topcoat Paint> Production Example 10 Into a container, 60 parts of epoxy resin (D-1) (Note 12), 40 parts of epoxy resin (D-2) (Note 13), 5 parts of titanium oxide, 5 parts of rust preventive pigment (B-3) (Note 5), 5 parts of fibrous inorganic compound (Note 18), and 12 parts of xylene were added and stirred and mixed to obtain a main component. Into another container, 20 parts of amino group-containing resin (Note 20), 25 parts of titanium oxide, and 2 parts of xylene were blended, stirred and mixed to obtain a crosslinking agent component, which was added to the above main component and stirred and mixed to obtain an epoxy resin-based topcoat paint (II-1).

[0090] Production Examples 11 to 26 In the above Production Example 10, epoxy resin-based topcoat paints (II-2) to (II-17) were produced in the same manner as in Production Example 10 except that the blending compositions were as shown in Tables 2 and 3 below.

[0091] <Painting> A steel plate with rust (rusty steel plate) having a size of approximately 150 × 70 × 3.2 mm was prepared as a substrate.

[0092] Example 1 The above rusty steel plate was air spray painted with the aqueous undercoat paint (I-1) obtained in Production Example 1 so that the dry film thickness was 60 μm, dried at 23°C for 24 hours, and then painted with the epoxy resin-based topcoat paint (II-1) obtained in Production Example 10 so that the dry film thickness was formed to be 1.25 mm, and dried at 23°C for 24 hours to obtain a test coated plate (X-1). The topcoat film formed by the epoxy resin-based topcoat paint (II-1) was obtained by applying a mold frame around the test coated panel after coating with the primer paint (I-1), pouring the topcoat paint into the mold frame, leveling the surface with a spatula, removing the mold frame, and then drying.

[0093] Examples 2 to 24 and Comparative Examples 1 to 7 In Example 1 above, each test coated panel (X-2) to (X-31) was obtained in the same manner as in Example 1, except that the paints used and the film thicknesses were as described in Tables 2 and 3.

[0094] [Table 2]

[0095] [Table 3]

[0096] (Note 12) Liquid bisphenol A type epoxy resin (D-1): Liquid bisphenol A type epoxy resin, epoxy equivalent 190, (Note 13) Liquid bisphenol F type epoxy resin (D-2): Liquid bisphenol F type epoxy resin, epoxy equivalent 190, (Note 14) Solid bisphenol A type epoxy resin (D-3): Solid bisphenol A type epoxy resin, epoxy equivalent 475, (Note 15) Liquid bisphenol A type epoxy resin (D-4): Liquid bisphenol A type epoxy resin, epoxy equivalent 250, (Note 16) Liquid bisphenol F type epoxy resin (D-5): Liquid bisphenol F type epoxy resin, epoxy equivalent 165, (Note 17) Solid bisphenol A type epoxy resin (D-6): Solid bisphenol A type epoxy resin, epoxy equivalent 2000, (Note 18) Fibrous inorganic compound: Rock wool fiber, average fiber length 125 μm, (Note 19) Glass flake: "RCF-140" (trade name, manufactured by Nippon Sheet Glass Co., Ltd.), average particle diameter 140 μm, (Note 20) Amino group-containing resin: Organic solvent-based aromatic polyamide amine, amine value 360.

[0097] <Evaluation test> (*) Appearance on rusty steel plate The appearance of each test coated plate obtained in the above examples and comparative examples was visually evaluated. ◎: There are no defects such as roughness, pinholes, and bumps on the coating film surface. 〇: Slight roughness is observed on the coating film surface, but there are no defects such as pinholes and bumps. △: Roughness is clearly observed on the coating film surface, but there are no defects such as pinholes and bumps. ×: There are defects such as pinholes and bumps on the coating film surface.

[0098] (*) Adhesion on rusty steel plate For each test coated plate, a pull-off adhesion test was performed using an adhesion tester manufactured by Ercometer Co., Ltd. The measurement position of each test plate was lightly polished with sandpaper to clean it, and then attached to the tester terminal using an adhesive. The coating film around the terminal was cut with a cutter, and the terminal was peeled off with the tester. The strength (MPa) and the coating film state at that time were observed. ◎: 5 MPa or more and cohesive failure of the coating film, or peeling from the rust layer exceeding 4 MPa ○: 2 MPa or more and less than 5 MPa with cohesive failure of the coating film, or peeling from the rust layer exceeding 2 MPa to 4 MPa △: 1 MPa or more and less than 2 MPa with cohesive failure of the coating film, or peeling from the rust layer exceeding 1 MPa to 2 MPa ×: Cohesive failure of the coating film at less than 1 MPa, or peeling from the rust layer at less than 1 MPa.

[0099] (*) Corrosion resistance on rusty steel plate For each test coated plate, a composite cycle corrosion test using a 5% sodium chloride aqueous solution specified in JIS K 5621 was carried out for 2400 hours, and the following criteria were used for evaluation by observing the surface of the general part of the test coated plate. ◎: No rust generation is observed. 〇: 1 to 5 points of rust with a diameter of less than 5 mm are observed on the test piece. △: Rust generation of 1 to 5 points is observed on the test piece and its size exceeds 5 mm, or rust generation of 6 to 15 points is observed regardless of the size of rust. ×: Rust generation of 15 points or more is observed on the test piece.

[0100] (*) Corrosion resistance to temperature change on rusty steel plate For each test coated plate obtained in the examples and comparative examples, a cycle test was carried out with 72 hours of ultraviolet irradiation, 72 hours of salt spray, and 24 hours of freezing (-20 °C) as one cycle, and this was repeated 25 times. After that, the coating film state was observed. ◎: No change at all before and after the cycle test. ○: Slight swelling is observed after the cycle test, but no rust has occurred. △: 1 to 5 rust occurrence parts or defects such as peeling and cracking are observed after the cycle test. ×: More than 5 rust occurrence parts or defects such as peeling and cracking are observed after the cycle test.

Claims

1. Step (1) of preparing an aqueous undercoat paint (I) by mixing the main component and the curing agent component of a two-component paint to contain an amino group-containing aqueous resin (A), a rust inhibitor component (B), and an epoxy group-containing resin emulsion (C); Step (2) of applying the aqueous undercoat paint (I) obtained in step (1) to the surface of a metallic substrate with remaining rust and drying it at room temperature to form an undercoat film; Step (3) of preparing an epoxy resin-based topcoat paint (II) by mixing the main component containing the epoxy resin component (D) of the two-component paint and the curing agent component containing an amino group-containing resin (E); A corrosion protection coating method including step (4) of applying the epoxy resin-based topcoat paint (II) obtained in step (3) onto the undercoat film and drying it at room temperature to form a topcoat film, wherein the epoxy equivalent of the epoxy resin component (D) contained in the epoxy resin-based topcoat paint (II) is 1700 or less, the epoxy resin-based topcoat paint (II) contains an organic solvent, the non-volatile content concentration during coating is 80% by mass or more, and the dry film thickness of the formed topcoat film is more than 1 mm and within the range of 5 mm or less.

2. The corrosion protection coating method according to claim 1, wherein the aqueous undercoat paint (I) is a two-component paint obtained by mixing a main component containing an amino group-containing aqueous resin (A) and a rust inhibitor component (B) and a curing agent component containing an epoxy group-containing resin emulsion (C).

3. The corrosion protection coating method according to claim 2, wherein the amino group-containing aqueous resin (A) is an amino group-containing resin emulsion (a) having a primary amino group using an epoxy resin (a1), a polyamine compound (a2), and a ketone compound (a3) as production raw materials.

4. The corrosion protection coating method according to any one of claims 1 to 3, wherein the aqueous undercoat paint (I) further contains at least one selected from fibrous inorganic compounds, polycarbodiimide compounds, and softeners.

5. The corrosion protection coating method according to any one of claims 1 to 4, wherein the epoxy resin component (D) contains a bisphenol A type epoxy resin and / or a bisphenol F type epoxy resin.

6. The corrosion protection coating method according to any one of claims 1 to 5, wherein the epoxy resin-based topcoat paint (II) contains a pigment component.

7. The corrosion protection coating method according to any one of claims 1 to 6, wherein the epoxy resin-based topcoat paint (II) contains a rust inhibitor component.

8. The anticorrosive coating method according to any one of claims 1 to 7, wherein the epoxy resin-based topcoat paint (II) contains a fibrous inorganic compound and / or glass flakes.

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