Composite coating structure suitable for protecting steel stand column of rain shed of railway station

Abstract

The invention discloses a composite coating. The composite coating comprises a primer layer and a water-based intumescent fireproof coating, the primer layer is formed by curing a bi-component epoxy zinc-aluminum coating, and the water-based intumescent fireproof coating is formed by curing a water-based intumescent fireproof coating. The invention further discloses raw material compositions and preparation methods of the two-component epoxy zinc-aluminum coating and the water-based intumescent fireproof coating. In addition, the invention further discloses application of the composite coating, especially application of the composite coating in surface coating of a steel stand column of a rain shed of a railway station. The composite coating provided by the invention not only can meet the actual fireproof requirement on site, but also can meet the long-time service requirement of the coating.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer coatings, and specifically relates to a composite coating suitable for surface protection of steel components, in particular to a fireproof composite coating suitable for steel columns of railway passenger station canopies. Background Art

[0002] Steel components are widely used in my country's railway passenger stations due to their good mechanical properties, large bearing capacity, light weight, good seismic performance, easy factory production, short construction period, energy saving and environmental protection, etc. For example, the steel columns of the station canopy that support the canopy. Since the steel columns of the station canopy play a load-bearing role, there are fire protection requirements for their coating, the purpose is to insulate and protect the steel columns, so that the steel columns can still maintain their strength for a certain period of time after the fire occurs, so as not to melt and collapse prematurely.

[0003] The coating system on the outer surface of the steel structure is generally a composite structure, including a primer layer, an intermediate paint layer and a topcoat layer. The primer mainly plays a role in rust prevention of the substrate. At present, it is mainly a two-component epoxy zinc-rich type, such as the Chinese invention patent application "A water-based epoxy anticorrosive antistatic primer and its preparation method" with publication number CN118580744A (publication date September 3, 2024). The primer includes component A and component B with a weight ratio of 100:10; component A includes water-based epoxy resin emulsion, conductive agent, anti-rust powder, talcum powder, titanium dioxide, barium sulfate, organic bentonite, fumed silica, cosolvent, dispersant, defoamer, wetting agent, adhesion promoter, thickener and deionized water; component B includes water-based epoxy curing agent, anti-flash rust agent, thickener, drying agent and deionized water. The intermediate paint layer can be a fire retardant coating, which plays a role in flame retardancy, fireproofing and heat insulation. The main function of the topcoat is weather resistance, giving the coating system a higher service life. At present, fire retardant coatings are divided into intumescent and non-intumescent fire retardant coatings. For example, the Chinese invention patent application "A non-intumescent steel structure fire retardant coating and its preparation method" with publication number CN118620419A (publication date September 10, 2024) discloses the formula of fire retardant coating as follows: 95-97 parts of dual-phase gypsum, 3-5 parts of inorganic lightweight insulating aggregate, 0.1-0.2 parts of retarder, 0.1 parts of glass fiber, 0.01 parts of foaming agent and 0.2 parts of water retaining agent. The Chinese invention patent application with publication number CN118620431A (publication date September 10, 2024) discloses a water-based inorganic intumescent fire retardant coating, its preparation method and application; the fire retardant coating is composed of the following raw material components by mass percentage: 30-50% potassium silicate solution, 4-15% styrene-acrylic emulsion, 2-8% talcum powder, 5-15% titanium dioxide, 1-10% heavy calcium, 5-15% aluminum hydroxide, 4-10% glass powder, 1-5% modified expandable graphite, 15-30% water and 1.7-2.7% additives. Intumescent fire retardant coatings are gradually replacing non-intumescent fire retardant coatings due to their advantages such as light weight and high adhesion. The above-mentioned primer, intermediate paint and topcoat as a whole require excellent adhesion and good compatibility between the layers of coating. In addition, the fire-retardant composite coating of the steel columns of the railway passenger station canopy needs to meet the actual anti-corrosion and fire protection requirements on site, as well as the need to meet the long-term service requirements. Summary of the invention

[0004] In view of the above problems, the present invention provides a composite coating suitable for surface protection of steel components, especially a fireproof composite coating suitable for steel columns of railway passenger station canopies. The composite coating comprises a two-component epoxy zinc-aluminum primer layer and a water-based intumescent fireproof coating. The composite coating of the present invention has good compatibility between the layers, strong adhesion, and outstanding corrosion resistance and fireproof performance.

[0005] To this end, the present invention adopts the following technical solution:

[0006] A composite coating, comprising a primer layer and a water-based intumescent fire-retardant coating; the primer layer is formed by curing a two-component epoxy zinc-aluminum coating, the two-component epoxy zinc-aluminum coating is composed of a component A and a component B which are stored separately at ordinary times and mixed when used, and the weight ratio of the component A to the component B is 3 to 8:1;

[0007] Wherein, the component A is composed of the following components in parts by weight:

[0008] 20-45 parts of waterborne epoxy resin emulsion, 55-75 parts of zinc-aluminum alloy powder, 0.5-1.5 parts of fumed silica, 1-5 parts of silica aerogel dispersion paste, 1-2 parts of bentonite, 2-6 parts of leveling agent, 2-6 parts of dispersant, 0.5-2 parts of defoaming agent;

[0009] The B component is an epoxy resin curing agent;

[0010] The water-based intumescent fire-retardant coating is formed by curing a water-based intumescent fire-retardant coating; the water-based intumescent fire-retardant coating comprises the following components in parts by weight:

[0011] 30-55 parts of silicone-acrylic resin, 6-16 parts of melamine, 18-30 parts of ammonium polyphosphate, 8-18 parts of pentaerythritol, 0.5-4 parts of refractory fiber, 4-26 parts of silica aerogel dispersion paste, 0.5-4 parts of fumed alumina, 1-4 parts of thickener, 1-4 parts of dispersant, 1-4 parts of film-forming aid, 0.5-3 parts of defoaming agent, 2-10 parts of titanium dioxide, and 0.5-4 parts of silane coupling agent.

[0012] Preferably, the dry film thickness of the primer layer is 80-100 μm; the dry film thickness of the water-based intumescent fire retardant coating is 1-5 mm.

[0013] Preferably, the weight ratio of component A to component B of the two-component epoxy zinc-aluminum coating is 4-6:1.

[0014] As a preferred embodiment, component A in the two-component epoxy zinc-aluminum coating is composed of the following components in parts by weight:

[0015] 30-35 parts of water-based epoxy resin emulsion, 60-70 parts of zinc-aluminum alloy powder, 0.5-1.0 parts of fumed silica, 2-4 parts of silica aerogel dispersion paste, 1-1.5 parts of bentonite, 2-4 parts of leveling agent, 2-4 parts of dispersant, and 0.5-1 part of defoaming agent.

[0016] For component A in the two-component epoxy zinc-aluminum coating:

[0017] Preferably, based on the total mass of the zinc-aluminum alloy powder, the percentage content of zinc is 78-88%, and the balance is aluminum.

[0018] Also preferably, the particle size of the zinc-aluminum alloy powder is 300 mesh.

[0019] Preferably, the waterborne epoxy resin emulsion is selected from the brand Epikote TM 3520-WY-55A, Epikote TM One of the water-based epoxy resin emulsions 3522-W-60A and DER-WB3002.

[0020] Among them, the brand Epikote TM 3520-WY-55A and Epikote TM The manufacturer of the water-based epoxy resin emulsion 3522-W-60A is HEXION, an American company; the manufacturer of the water-based epoxy resin emulsion with the brand DER-WB3002 is DOW or Olin, an American company.

[0021] More preferably, the waterborne epoxy resin emulsion is selected from Epikote TM 3520-WY-55A and Epikote TM One of the water-based epoxy resin emulsions of 3522-W-60A.

[0022] Preferably, the fumed silica is selected from and One of them.

[0023] Fumed silica is also called fumed white carbon black. and The manufacturer is EVONIK of Germany.

[0024] Preferably, the silica aerogel content in the silica aerogel dispersion paste is 20% or 30%.

[0025] Preferably, the dispersant is selected from and One of them.

[0026] Preferably, the leveling agent is

[0027] Preferably, the defoaming agent is selected from one of BYK@-024 and Ota Chemical D-80.

[0028] The present invention also provides a method for preparing the component A, comprising the following steps:

[0029] Prepare the raw material components according to the ratio; add the water-based epoxy resin emulsion, dispersant and defoamer into a container with a stirring device, and stir for 10 to 20 minutes; add bentonite, silica aerogel dispersion paste and fumed silica, maintain the rotation speed, and stir for 20 to 40 minutes; finally, add zinc-aluminum alloy powder and leveling agent, and stir evenly to obtain component A.

[0030] Preferably, the stirring speed is 400-600 rpm.

[0031] Preferably, the component B in the two-component epoxy zinc-aluminum coating is a polyamine curing agent, more preferably a poly-fatty amine curing agent, and particularly preferably diethylenetriamine or triethylenetetramine.

[0032] As a preferred embodiment, the water-based intumescent fire retardant coating of the present invention comprises the following components in parts by weight:

[0033] 35-45 parts of silicone-acrylic resin, 8-12 parts of melamine, 20-28 parts of ammonium polyphosphate, 8-14 parts of pentaerythritol, 0.5-2 parts of refractory fiber, 8-18 parts of silica aerogel dispersion paste, 0.5-2 parts of fumed alumina, 1-2 parts of thickener, 1-2 parts of dispersant, 1-2 parts of film-forming aid, 0.5-2 parts of defoaming agent, 2-8 parts of titanium dioxide, and 0.5-1.5 parts of silane coupling agent.

[0034] As a more preferred embodiment, the water-based intumescent fire retardant coating of the present invention comprises the following components in parts by weight:

[0035] 38-42 parts of silicone-acrylic resin, 8-12 parts of melamine, 20-28 parts of ammonium polyphosphate, 10-14 parts of pentaerythritol, 1-2 parts of refractory fiber, 8-18 parts of silica aerogel dispersion paste, 1-2 parts of fumed alumina, 1-2 parts of thickener, 1-2 parts of dispersant, 1-2 parts of film-forming aid, 0.5-2 parts of defoaming agent, 4-6 parts of titanium dioxide, and 1-1.5 parts of silane coupling agent.

[0036] The raw materials of the water-based intumescent fire retardant coating are:

[0037] The silicone-acrylic resin can be selected from the commercially available silicone-acrylic resin 8912 produced by Qingdao Gudao Technology Co., Ltd. or the silicone-acrylic resin RS-3799A produced by Badfu.

[0038] Preferably, the refractory fiber is aluminum silicate fiber with a length of less than 1 cm and a refractory temperature of more than 800°C.

[0039] Preferably, the particle size of the fumed alumina is 100 to 300 nm.

[0040] Preferably, the thickener is selected from RHEOBYK-425 or RHEOBYK-7610.

[0041] Preferably, the dispersant is selected from aqueous wetting dispersants or

[0042] Preferably, the film-forming aid is lauryl alcohol ester.

[0043] Preferably, the titanium dioxide is rutile titanium dioxide with a particle size of 45 to 80 μm.

[0044] Preferably, in the raw materials of the water-based intumescent fire retardant coating, the defoaming agent is

[0045] The present invention also provides a method for preparing the water-based intumescent fire retardant coating, comprising the following operations:

[0046] Prepare the components of the raw materials according to the proportions; add silicone-acrylic resin, melamine, ammonium polyphosphate, pentaerythritol, refractory fiber, silica aerogel dispersion paste, dispersant, defoamer and titanium dioxide in sequence into a device with a stirring device, and stir for 60 to 100 minutes; then add fumed alumina, thickener, surface additive and silane coupling agent, and continue stirring for 60 to 100 minutes to obtain the product.

[0047] Preferably, the stirring speed is 400-600 rpm.

[0048] Preferably, the composite coating further comprises a topcoat layer, and the water-based intumescent fire-retardant coating is between the topcoat layer and the primer layer.

[0049] Preferably, the topcoat layer is formed by curing a fluorocarbon resin coating or a polyurethane coating.

[0050] In addition, the present invention also provides application of the composite coating in coating the surface of a steel component.

[0051] In particular, the present invention provides the use of the composite coating in the surface coating of steel columns of a railway passenger station canopy.

[0052] Therefore, another object of the present invention is to provide a construction process for coating the surface of a steel member, comprising using the two-component epoxy zinc-aluminum coating of the present invention as a primer and using the water-based intumescent fire-retardant coating as a fire-retardant coating, comprising the following steps:

[0053] S1. Clean and remove rust from the surface of steel components to be painted, so that the surface reaches Sa2.5 level or above;

[0054] S2. The components A and B are mixed evenly according to the weight ratio, sprayed or brushed on the surface of the Sa2.5 level or above, dried naturally, and repeatedly sprayed or brushed until the dry film thickness reaches 80 to 100 μm;

[0055] S3. Spray or brush the water-based intumescent fire retardant coating on the primer layer obtained in step S2, and dry it naturally; repeat the spraying or brushing until the dry film thickness reaches 1 to 5 mm.

[0056] Preferably, the construction process further comprises, after step S3:

[0057] S4. Spray or apply a fluorocarbon resin coating or a polyurethane coating on the fire retardant coating obtained in step S3, and dry it naturally; repeat the spraying or applying until the dry film thickness reaches 3 to 5 mm.

[0058] The composite coating provided by the present invention, including a primer layer and a water-based intumescent fire-retardant coating, is particularly suitable for coating steel columns of railway station canopies, and can meet both the actual fire protection requirements on site and the long-term service requirements of the coating itself. DETAILED DESCRIPTION

[0059] The present invention is described below with reference to specific examples. It will be appreciated by those skilled in the art that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention in any way.

[0060] The experimental methods in the following examples are conventional methods unless otherwise specified. The raw materials, reagents, etc. used in the following examples are commercially available products unless otherwise specified. The manufacturers and product information of some raw materials and reagents are as follows:

[0061] Water-based epoxy resin emulsion: American Hansen HEXION, Epikote TM 3520-WY-55A;

[0062] Zinc-aluminum alloy powder: Dinghong (Shanghai) New Material Technology Co., Ltd., ZnAl12, 300 mesh;

[0063] Fumed silica: EVONIK A200;

[0064] Silica aerogel dispersion paste: Anhui Keang Nanotechnology Co., Ltd., aerogel content 30%;

[0065] Leveling agent: BYK Chemical,

[0066] Dispersant: BYK Chemical,

[0067] Defoamer: BYK Chemical,

[0068] Silicone acrylic resin: Qingdao Gudao Technology Co., Ltd., Budford, RS-3799A

[0069] Thickener: BYK RHEOBYK-425, RHEOBYK-7610;

[0070] Fumed alumina: Cabot Corporation, PC-401; EVONIK, AluC;

[0071] Silane coupling agent: Shanghai MacLean Biochemical Technology Co., Ltd., N-aminoethyl-γ-aminopropyltrimethoxysilane.

[0072] Embodiments 1 to 4 A two-component epoxy zinc-aluminum coating

[0073] The two-component epoxy zinc-aluminum coating is composed of component A and component B which are stored separately at ordinary times and mixed evenly when used. The specific compositions of component A and component B are shown in Table 1 (1 part by weight = 1 kg).

[0074] Table 1 Composition of two-component epoxy zinc-aluminum coatings of Examples 1 to 4 (parts by weight)

[0075]

[0076] Embodiments 5 to 8 A water-based intumescent fire retardant coating

[0077] The specific composition of the water-based intumescent fire retardant coating is shown in Table 2 (1 part by weight = 1 kg).

[0078] Table 2 Composition of water-based intumescent fire retardant coatings of Examples 5 to 8 (parts by weight)

[0079]

[0080] Add silicone-acrylic resin, melamine, ammonium polyphosphate, pentaerythritol, refractory fiber, silica aerogel dispersion paste, dispersant, defoaming agent and titanium dioxide into a stirring kettle in sequence, rotate at 500 rpm and stir for 60 minutes; then add fumed alumina, thickener, surface additive and silane coupling agent, maintain the rotation speed and continue stirring for 60 minutes to obtain the product.

[0081] Comparative Examples 1 to 5 A two-component epoxy zinc-aluminum coating

[0082] The two-component epoxy zinc-aluminum coating is composed of component A and component B which are stored separately and mixed evenly when used. The specific compositions of component A and component B are shown in Table 3 (1 part by weight = 1 kg). Component A is prepared according to the same process as in Example 1.

[0083] Table 3 Composition of two-component epoxy zinc-aluminum coatings of comparative examples 1-5 (parts by weight)

[0084]

[0085]

[0086] Comparative Examples 6 to 12 A water-based intumescent fire retardant coating

[0087] The specific composition of the water-based intumescent fire retardant coating is shown in Table 4 (1 part by weight = 1 kg), and is prepared according to the same process as Example 5.

[0088] Table 4 Composition of water-based intumescent fire retardant coatings of Comparative Examples 6 to 12 (parts by weight)

[0089]

[0090] Test Case

[0091] 1. Performance determination of two-component epoxy zinc-aluminum coating

[0092] The two-component epoxy zinc-aluminum coating is used as the primer of the composite coating of the present invention. Its adhesion to the metal steel surface, impact resistance, flexibility, salt spray resistance and other properties are investigated according to the method shown in Table 5. The results are shown in Table 6.

[0093] Table 5 Performance index and test basis of primer layer of composite coating for steel components

[0094] Serial number project Test method based on 1 State in container (components A and B) Visual inspection 2 Adhesion, MPa GB / T 5210 3 Impact resistance, cm GB / T 1732 4 Flexibility, mm GB / T 6742 5 Salt spray resistance GB / T 10125 6 Whether it is cracked Visual inspection

[0095] Table 6 Performance test results of two-component epoxy zinc-aluminum coating (primer) of each embodiment and comparative example

[0096]

[0097] 2. Performance determination of waterborne intumescent fire retardant coatings

[0098] The water-based intumescent fire-retardant coating of the composite coating of the present invention is formed by a water-based intumescent fire-retardant coating. The fire-retardant coating formed by the water-based intumescent fire-retardant coating of Examples 5 to 8 and the primer layer formed by the two-component epoxy zinc-aluminum coating of Example 1 were investigated for adhesion, thickness after self-combustion, fire resistance and other properties according to the method shown in Table 7. The fire-retardant coating formed by the water-based intumescent fire-retardant coating of Comparative Examples 6 to 12 and the primer layer formed by the two-component epoxy zinc-aluminum coating of Example 1, thickness after self-combustion, fire resistance and other properties were measured and shown in Table 9.

[0099] Table 7 Fire retardant coating performance indicators and test basis

[0100] Serial number project Test method based on 1 Adhesion, MPa GB / T 5210 2 Thickness, mm GB / T 4956 3 Fire resistance limit, min GB 14907 4 Whether it is cracked Visual inspection

[0101] Table 8 Test results of fire retardant coating properties formed by water-based intumescent fire retardant coatings of Examples 5 to 8

[0102]

[0103] Table 9 Test results of fire retardant coating properties formed by water-based intumescent fire retardant coatings of comparative examples 6 to 12

[0104]

[0105] In summary, the present invention provides a two-component epoxy zinc-aluminum coating and a water-based intumescent fire-retardant coating, and a composite coating comprising a primer layer and a water-based intumescent fire-retardant coating cured from the two components. The composite coating is particularly suitable for surface protection of steel components. The composite coating of the present invention has good compatibility between the layers, strong adhesion, outstanding corrosion resistance and fireproof performance, and is particularly suitable for fire-retardant composite coatings for steel columns of railway passenger station canopies.

Claims

1. A composite coating, comprising a primer layer and a water-based intumescent fire-retardant coating; the primer layer is formed by curing a two-component epoxy zinc-aluminum coating, the two-component epoxy zinc-aluminum coating is composed of a component A and a component B which are stored separately at ordinary times and mixed when used, and the weight ratio of the component A to the component B is 3 to 8:1, preferably 4 to 6:1; in, The A component is composed of the following components in parts by weight: 20-45 parts of waterborne epoxy resin emulsion, 55-75 parts of zinc-aluminum alloy powder, 0.5-1.5 parts of fumed silica, 1-5 parts of silica aerogel dispersion paste, 1-2 parts of bentonite, 2-6 parts of leveling agent, 2-6 parts of dispersant, 0.5-2 parts of defoaming agent; The B component is an epoxy resin curing agent; The water-based intumescent fire-retardant coating is formed by curing a water-based intumescent fire-retardant coating; the water-based intumescent fire-retardant coating comprises the following components in parts by weight: 30-55 parts of silicone-acrylic resin, 6-16 parts of melamine, 18-30 parts of ammonium polyphosphate, 8-18 parts of pentaerythritol, 0.5-4 parts of refractory fiber, 4-26 parts of silica aerogel dispersion paste, 0.5-4 parts of fumed alumina, 1-4 parts of thickener, 1-4 parts of dispersant, 1-4 parts of film-forming aid, 0.5-3 parts of defoamer, 2-10 parts of titanium dioxide, and 0.5-4 parts of silane coupling agent; Preferably, the dry film thickness of the primer layer is 80-100 μm; the dry film thickness of the water-based intumescent fire retardant coating is 1-5 mm.

2. The composite coating according to claim 1, characterized in that: Component A in the two-component epoxy zinc-aluminum coating is composed of the following components in parts by weight: 30-35 parts of waterborne epoxy resin emulsion, 60-70 parts of zinc-aluminum alloy powder, 0.5-1.0 parts of fumed silica, 2-4 parts of silica aerogel dispersion paste, 1-1.5 parts of bentonite, 2-4 parts of leveling agent, 2-4 parts of dispersant, 0.5-1 part of defoaming agent; Preferably, in the component A, based on the total mass of the zinc-aluminum alloy powder, the percentage content of zinc is 78-88%, and the balance is aluminum; Also preferably, the particle size of the zinc-aluminum alloy powder is 300 mesh; Preferably, in the component A, the waterborne epoxy resin emulsion is selected from the brand Epikote TM 3520-WY-55A, Epikote TM One of the waterborne epoxy resin emulsions 3522-W-60A and DER-WB3002; More preferably, the waterborne epoxy resin emulsion is selected from Epikote TM 3520-WY-55A and Epikote TM One of the water-based epoxy resin emulsions of 3522-W-60A; Preferably, in the A component, the fumed silica is selected from 200, 300 and One of 380; Preferably, in the component A, the silica aerogel content in the silica aerogel dispersion paste is 20% or 30%; Preferably, in the A component, the dispersant is selected from and One of; Preferably, in the component A, the leveling agent is Preferably, in the component A, the defoamer is selected from one of BYK@-024 and Datian Chemical D-80.

3. The composite coating according to claim 1, characterized in that: The preparation method of the A component comprises the following operations: Prepare the raw material components according to the ratio; add the water-based epoxy resin emulsion, dispersant and defoamer into a container with a stirring device, and stir for 10 to 20 minutes; add bentonite, silica aerogel dispersion paste and fumed silica, keep the speed and stir for 20 to 40 minutes; finally add zinc-aluminum alloy powder and leveling agent, and stir evenly to obtain component A; Preferably, the stirring speed is 400-600 rpm.

4. The composite coating according to claim 1, characterized in that: The component B in the two-component epoxy zinc-aluminum coating is a polyamine curing agent, more preferably a poly-fatty amine curing agent, and particularly preferably diethylenetriamine or triethylenetetramine.

5. The composite coating according to claim 1, characterized in that: The water-based intumescent fire-retardant coating comprises the following components in parts by weight: 35-45 parts of silicone-acrylic resin, 8-12 parts of melamine, 20-28 parts of ammonium polyphosphate, 8-14 parts of pentaerythritol, 0.5-2 parts of refractory fiber, 8-18 parts of silica aerogel dispersion paste, 0.5-2 parts of fumed alumina, 1-2 parts of thickener, 1-2 parts of dispersant, 1-2 parts of film-forming aid, 0.5-2 parts of defoamer, 2-8 parts of titanium dioxide, 0.5-1.5 parts of silane coupling agent; Preferably, the water-based intumescent fire retardant coating comprises the following components in parts by weight: 38-42 parts of silicone-acrylic resin, 8-12 parts of melamine, 20-28 parts of ammonium polyphosphate, 10-14 parts of pentaerythritol, 1-2 parts of refractory fiber, 8-18 parts of silica aerogel dispersion paste, 1-2 parts of fumed alumina, 1-2 parts of thickener, 1-2 parts of dispersant, 1-2 parts of film-forming aid, 0.5-2 parts of defoaming agent, 4-6 parts of titanium dioxide, and 1-1.5 parts of silane coupling agent.

6. The composite coating according to claim 1 or 5, characterized in that: Among the raw materials of the water-based intumescent fire retardant coating, the silicone-acrylic resin can be selected from the commercially available silicone-acrylic resin 8912 produced by Qingdao Gudao Technology Co., Ltd. or the silicone-acrylic resin RS-3799A produced by Badfu; Preferably, in the raw materials of the water-based intumescent fire-retardant coating, the refractory fiber is aluminum silicate fiber, with a length of less than 1 cm and a refractory temperature of more than 800°C; Preferably, in the raw materials of the water-based intumescent fire retardant coating, the particle size of the fumed alumina is 100 to 300 nm; Preferably, in the raw materials of the waterborne intumescent fire retardant coating, the thickener is selected from RHEOBYK-425 or RHEOBYK-7610; Preferably, in the raw materials of the water-based intumescent fire retardant coating, the dispersant is selected from water-based wetting dispersants or Preferably, in the raw materials of the waterborne intumescent fire retardant coating, the film-forming aid is lauryl alcohol ester; Preferably, in the raw materials of the water-based intumescent fire retardant coating, the titanium dioxide is rutile titanium dioxide with a particle size of 45 to 80 μm; Preferably, in the raw materials of the water-based intumescent fire retardant coating, the defoaming agent is 7. The composite coating according to claim 1, 5 or 6, characterized in that: The preparation method of the water-based intumescent fire retardant coating comprises the following operations: Prepare the components of the raw materials according to the proportion; add silicone-acrylic resin, melamine, ammonium polyphosphate, pentaerythritol, refractory fiber, silica aerogel dispersion paste, dispersant, defoamer and titanium dioxide in a device with a stirring device in sequence, and stir for 60 to 100 minutes; then add fumed alumina, thickener, surface additive and silane coupling agent, and continue stirring for 60 to 100 minutes to obtain; Preferably, the stirring speed is 400-600 rpm.

8. The composite coating according to any one of claims 1 to 7, characterized in that: The composite coating further comprises a topcoat layer, and the water-based intumescent fire-retardant coating is between the topcoat layer and the primer layer; Preferably, the topcoat layer is formed by curing a fluorocarbon resin coating or a polyurethane coating.

9. Use of the composite coating according to any one of claims 1 to 8 in coating the surface of steel components; In particular, the composite coating according to any one of claims 1 to 8 is used in the surface coating of steel columns of railway passenger station canopies.

10. A construction process for coating the surface of a steel member, comprising using a two-component epoxy zinc-aluminum coating as a primer and a water-based intumescent fire-retardant coating as a fire-retardant coating, wherein the two-component epoxy zinc-aluminum coating is as defined in any one of claims 1 to 4, and the water-based intumescent fire-retardant coating is as defined in claim 1, 5, 6 or 7; the construction process comprises the following steps: S1. Clean and remove rust from the surface of steel components to be painted, so that the surface reaches Sa2.5 level or above; S2. The components A and B are mixed evenly according to the weight ratio, sprayed or brushed on the surface of the Sa2.5 level or above, dried naturally, and repeatedly sprayed or brushed until the dry film thickness reaches 80 to 100 μm; S3. Spray or apply the water-based intumescent fire retardant coating on the primer layer obtained in step S2 and dry it naturally; repeat spraying or applying until the dry film thickness reaches 1 to 5 mm; Preferably, the construction process further comprises, after step S3: S4. Spray or apply a fluorocarbon resin coating or a polyurethane coating on the fire retardant coating obtained in step S3 and dry it naturally; Repeat spraying or brushing until the dry film reaches the specified thickness.

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