Water-based pre-coating primer and preparation method thereof

Abstract

The invention relates to the technical field of coatings, and particularly discloses a water-based pre-coating primer and a preparation method thereof. The water-based pre-coating primer comprises a component A and a component B, the component A comprises the following components: ethylene glycol monobutyl ether, aluminum powder, a passivation additive, a waterborne epoxy emulsion, deionized water, a dispersing agent, a defoaming agent, zinc-iron powder, waterborne aluminum paste, zinc phosphate, bentonite, fumed silica, a base material wetting agent, a flash rust inhibitor and a thickening agent; and the component B is an epoxy curing agent. The water-based pre-coating primer prepared by the invention is environment-friendly, good in adhesive force, free of secondary polishing and good in anti-rust performance.

Description

Technical Field

[0001] This application relates to the technical field of coatings, and in particular to a waterborne pre - coated primer and a preparation method thereof. Background Art

[0002] In the field of rail transit, coating waterborne pre - coated primers on facilities such as rails and trains is a common anti - corrosion and surface repair method. Traditionally, when the original coating on the metal surface is damaged or worn, usually cumbersome pretreatment steps are required, including sanding, cleaning, and rust removal, to remove the damaged paint layer or oxide layer, and then a new coating is sprayed again. This process is not only time - consuming and laborious, but also may lead to a reduction in production efficiency. And in some cases, when coating on metal rails, it may affect the welding quality of subsequent welding operations, resulting in defects in the weld seam, such as cracks, pores, or insufficient strength.

[0003] In view of this background, developing a waterborne pre - coated primer that simultaneously meets the requirements of rapid drying, excellent mechanical properties, no need for secondary sanding, simple construction process, excellent anti - corrosion efficiency, and can fully adapt to various welding processes such as manual welding, automatic welding, and submerged arc welding, effectively balancing anti - corrosion and welding performance, is of great significance for promoting the technological innovation of pre - coated primers for railway wagons. Summary of the Invention

[0004] In order to solve at least one of the above - mentioned technical problems and develop a pre - coated primer with good adhesion, simple construction process, good rust - proof performance, and ensuring the welding performance of the metal surface, this application provides a waterborne pre - coated primer and a preparation method thereof.

[0005] On the one hand, a waterborne pre - coated primer provided by this application includes component A and component B with a weight ratio of 8:1. Component A includes the following components in parts by weight: 40 - 60 parts of ethylene glycol monobutyl ether, 40 - 60 parts of aluminum powder, 10 - 20 parts of passivation aid, 350 - 450 parts of waterborne epoxy emulsion, 150 - 180 parts of deionized water, 5 - 10 parts of dispersant, 1 - 5 parts of defoamer, 200 - 300 parts of zinc iron powder, 100 - 130 parts of waterborne aluminum silver paste, 20 - 40 parts of zinc phosphate, 2 - 8 parts of bentonite, 2 - 8 parts of fumed silica, 1 - 5 parts of substrate wetting agent, 5 - 12 parts of anti - flash rust agent, 1 - 5 parts of thickener. Component B is an epoxy curing agent.

[0006] By adopting the above technical solutions, the present application is a waterborne pre-coated primer with low VOC (volatile organic compound) content, meeting environmental protection standards and having little impact on the environment and the health of construction workers. The formulation contains zinc iron powder and zinc phosphate to provide cathodic protection. The passivation aid and anti-flash rust agent can effectively prevent the corrosion of metal substrates and enhance the anti-corrosion ability of the primer. The epoxy emulsion, as the main film-forming substance, reacts with the component B epoxy curing agent to form a tough cross-linked network, providing excellent adhesion and mechanical properties. Aluminum powder and waterborne aluminum silver paste provide metallic luster and hiding power, making the coating have a good appearance effect. Components such as bentonite, fumed silica, and thickener work together to improve the storage stability and construction stability of the coating, prevent sedimentation and delamination, and ensure the consistency of product quality. At the same time, the substrate wetting agent and dispersant in the formulation ensure good wetting and uniform coating of the primer on various substrates.

[0007] Optionally, the epoxy emulsion includes acrylic-modified epoxy emulsion and waterborne epoxy emulsion, and the weight ratio of the acrylic-modified epoxy emulsion to the waterborne epoxy emulsion is (0.1 - 0.8):1.

[0008] By adopting the above technical solutions, the present application combines the acrylic-modified epoxy emulsion and the waterborne epoxy emulsion and uses them as the main film-forming substances of the waterborne pre-coated primer. The acrylic-modified epoxy emulsion can provide good weather resistance and flexibility, while the waterborne epoxy emulsion provides stronger chemical resistance and adhesion, enabling the waterborne pre-coated primer to be directly coated on the damaged original paint layer, having good covering properties, reducing the cleaning of the original paint layer, and improving efficiency.

[0009] Optionally, the preparation method of the acrylic-modified epoxy emulsion includes the following steps: A1. Prepare materials according to 20 - 30 parts by weight of epoxy resin E-20, 15 - 25 parts by weight of ethylene glycol monobutyl ether, 15 - 25 parts by weight of n-butanol, 5 - 8 parts by weight of methacrylic acid, 5 - 8 parts by weight of butyl acrylate, 5 - 10 parts by weight of styrene, 1 - 2 parts by weight of dibenzoyl peroxide, 5 - 8 parts by weight of triethylamine, and 25 - 35 parts by weight of deionized water; A2. Mix epoxy resin E-20, ethylene glycol monobutyl ether, and n-butanol, heat and stir to raise the temperature to 110 - 120°C to obtain mixture I; A3. Drop methacrylic acid, butyl acrylate, and styrene into the mixture prepared in step A1, then add dibenzoyl peroxide, and keep the temperature at 110 - 120°C under nitrogen protection for 2.5 - 3 h to obtain mixture II; A4. After cooling the mixture II to 50 - 55°C, add triethylamine to neutralize and form a salt, keep the temperature for 0.5 - 1 h, then add deionized water, and disperse at a high speed of 2500 - 3000 rpm for 0.5 - 1 h to obtain the acrylic-modified epoxy emulsion.

[0010] Optionally, the component A further includes 20-40 parts by weight of halloysite nanotube-inhibitor complex.

[0011] By adopting the above technical solution, the present application also adds a halloysite nanotube-inhibitor complex, which can significantly improve the anti-corrosion performance, mechanical properties, rheological properties and weather resistance of the primer. Halloysite nanotubes have a large specific surface area and cavity structure, which can load inhibitors and improve the stability and dispersibility of inhibitors in the primer. Moreover, halloysite nanotubes also have good environmental protection properties.

[0012] Optionally, the preparation method of the halloysite nanotube-inhibitor complex includes the following steps: B1. Add hydrochloric acid solution with a concentration of (3-5) mol / L to halloysite nanotubes, heat and stir for 4-6 h under water bath conditions, centrifuge, filter, wash and grind to obtain halloysite nanotubes etched with hydrochloric acid; B2. Mix the halloysite nanotubes etched with hydrochloric acid obtained in step B1, an inhibitor and deionized water, ultrasonically disperse for 40-60 min, and then vacuum dry the obtained suspension; B3. After the vacuum drying is completed, perform centrifugation to separate the solid phase, wash the solid phase, dry it, and grind it into powder to obtain the halloysite nanotube-inhibitor complex.

[0013] Optionally, the weight ratio of halloysite nanotubes to hydrochloric acid solution in step B1 is (5-7):(60-80).

[0014] Optionally, the weight ratio of the inhibitor, deionized water in step B2 and halloysite nanotubes in step B1 is (6-8):(50-60):1.

[0015] Optionally, the inhibitor is modified aluminum tripolyphosphate.

[0016] Optionally, the anti-flash rust agent is a titanate coupling agent, and the epoxy curing agent includes an aqueous amine curing agent and deionized water with a weight ratio of 4:1.

[0017] Optionally, the passivation aid is zinc molybdate, the dispersant is fatty acid polyethylene glycol, the defoaming agent is polydimethylsiloxane, the anti-flash rust agent is a titanate coupling agent, the substrate wetting agent is sodium dodecyl sulfonate, and the thickening agent is ethoxy polyurethane polymer.

[0018] In a second aspect, the present application provides a preparation method of the above aqueous pre-coated primer, including the following steps: S1. Mix and disperse ethylene glycol monobutyl ether, aluminum powder and a passivation aid for 10-20 min to obtain mixture I, and let it stand for 22-24 h; S2. Mix the mixture I and the epoxy emulsion, then add a dispersant, an antifoaming agent, a water-based aluminum silver paste, a substrate wetting agent, a flash rust inhibitor, and a thickener and mix and disperse them to obtain a mixture II. S3. Mix and grind zinc iron powder, zinc phosphate, bentonite, and fumed silica to a fineness ≤ 30 μm to obtain a mixed material, and then mix and disperse the mixed material with the mixture II and deionized water to obtain component A. S4. Mix component A and component B to prepare the water-based pre-coated primer.

[0019] By adopting the above technical solution, the preparation method of the water-based pre-coated primer of the present application is simple, suitable for industrial production, the prepared water-based pre-coated primer is easy to construct, has a fast drying speed, simplifies the construction process, and improves work efficiency.

[0020] In summary, the present invention includes at least one of the following beneficial technical effects: 1. The present application is a water-based pre-coated primer with a low VOC (volatile organic compound) content, meeting environmental protection standards and having little impact on the environment and the health of construction workers. The formula contains zinc iron powder and zinc phosphate to provide cathodic protection, and the passivation aid and flash rust inhibitor can effectively prevent the corrosion of metal substrates and enhance the anti-corrosion ability of the primer. The epoxy emulsion is used as the main film-forming substance and reacts with the B-component epoxy curing agent to form a tough cross-linked network, providing excellent adhesion and mechanical properties. Aluminum powder and water-based aluminum silver paste provide metallic luster and covering power, making the coating have a good appearance effect. Components such as bentonite, fumed silica, and thickener act together to improve the storage stability and construction stability of the coating, prevent sedimentation and stratification, and ensure the consistency of product quality. At the same time, the substrate wetting agent and dispersant in the formula ensure good wetting and uniform coating of the primer on various substrates.

[0021] 2. The preparation method of the water-based pre-coated primer of the present application is simple, suitable for industrial production, the prepared water-based pre-coated primer is easy to construct, has a fast drying speed, simplifies the construction process, and improves work efficiency. Specific Embodiments

[0022] The following further elaborates on the present application with reference to embodiments. Specific Examples

[0023] Preparation Example 1 This preparation example provides an acrylic-modified epoxy emulsion, and its preparation method includes the following steps: A1. Prepare materials according to 20 parts by weight of epoxy resin E, 15 parts of ethylene glycol monobutyl ether, 15 parts of n-butanol, 5 parts of methacrylic acid, 5 parts of butyl acrylate, 5 parts of styrene, 1 part of dibenzoyl peroxide, 5 parts of triethylamine, and 25 parts of deionized water. A2. Mix epoxy resin E-20, ethylene glycol monobutyl ether and n-butanol, heat and stir to raise the temperature to 110 °C to obtain mixture I; A3. Drop methacrylic acid, butyl acrylate and styrene into the mixture obtained in step A1, add benzoyl peroxide, and keep the temperature at 110 °C under nitrogen protection for 3 h to obtain mixture II; A4. After cooling mixture II to 50 °C, add triethylamine to neutralize and form a salt. After keeping the temperature for 1 h, add deionized water and disperse at a high speed at 2500 rpm for 1 h to obtain acrylic acid-modified epoxy emulsion.

[0024] Preparation Example 2 This preparation example provides an acrylic acid-modified epoxy emulsion, and its preparation method includes the following steps: A1. Prepare materials according to 25 parts by weight of epoxy resin E-20, 20 parts of ethylene glycol monobutyl ether, 20 parts of n-butanol, 6 parts of methacrylic acid, 7 parts of butyl acrylate, 8 parts of styrene, 2 parts of benzoyl peroxide, 6 parts of triethylamine, and 30 parts of deionized water; A2. Mix epoxy resin E-20, ethylene glycol monobutyl ether and n-butanol, heat and stir to raise the temperature to 115 °C to obtain mixture I; A3. Drop methacrylic acid, butyl acrylate and styrene into the mixture obtained in step A1, add benzoyl peroxide, and keep the temperature at 115 °C under nitrogen protection for 3 h to obtain mixture II; A4. After cooling mixture II to 53 °C, add triethylamine to neutralize and form a salt. After keeping the temperature for 1 h, add deionized water and disperse at a high speed at 2800 rpm for 1 h to obtain acrylic acid-modified epoxy emulsion.

[0025] Preparation Example 3 This preparation example provides an acrylic acid-modified epoxy emulsion, and its preparation method includes the following steps: A1. Prepare materials according to 30 parts by weight of epoxy resin E-20, 25 parts of ethylene glycol monobutyl ether, 25 parts of n-butanol, 8 parts of methacrylic acid, 8 parts of butyl acrylate, 10 parts of styrene, 2 parts of benzoyl peroxide, 8 parts of triethylamine, and 35 parts of deionized water; A2. Mix epoxy resin E-20, ethylene glycol monobutyl ether and n-butanol, heat and stir to raise the temperature to 120 °C to obtain mixture I; A3. Drop methacrylic acid, butyl acrylate and styrene into the mixture obtained in step A1, add benzoyl peroxide, and keep the temperature at 120 °C under nitrogen protection for 2.5 h to obtain mixture II; A4. After cooling the mixture II to 55 °C, add triethylamine to neutralize and form a salt. After maintaining the reaction for 0.5 h, add deionized water and disperse it at a high speed at a rotation speed of 3000 rpm for 0.5 h to obtain an acrylic acid-modified epoxy emulsion.

[0026] Preparation Example 4 This preparation example provides a halloysite nanotube-inhibitor complex, and its preparation method includes the following steps: B1. Add a hydrochloric acid solution with a concentration of 3 mol / L to the halloysite nanotubes, heat and stir for 6 h under water bath conditions, centrifuge, filter, wash, and grind to obtain halloysite nanotubes etched with hydrochloric acid; B2. Mix the halloysite nanotubes etched with hydrochloric acid obtained in step B1, the inhibitor, and deionized water, ultrasonically disperse for 60 min, and then vacuum dry the obtained suspension; B3. After the vacuum drying is completed, perform centrifugation to separate the solid phase, wash the solid phase, dry it, and grind it into powder to obtain the halloysite nanotube-inhibitor complex.

[0027] The weight ratio of the halloysite nanotubes to the hydrochloric acid solution in step B1 is 5:60.

[0028] The weight ratio of the inhibitor, deionized water, and the halloysite nanotubes in step B1 in step B2 is 6:50:1, and the inhibitor is modified aluminum tripolyphosphate.

[0029] Preparation Example 5 This preparation example provides a halloysite nanotube-inhibitor complex, and its preparation method includes the following steps: B1. Add a hydrochloric acid solution with a concentration of 4 mol / L to the halloysite nanotubes, heat and stir for 5 h under water bath conditions, centrifuge, filter, wash, and grind to obtain halloysite nanotubes etched with hydrochloric acid; B2. Mix the halloysite nanotubes etched with hydrochloric acid obtained in step B1, the inhibitor, and deionized water, ultrasonically disperse for 50 min, and then vacuum dry the obtained suspension; B3. After the vacuum drying is completed, perform centrifugation to separate the solid phase, wash the solid phase, dry it, and grind it into powder to obtain the halloysite nanotube-inhibitor complex.

[0030] The weight ratio of the halloysite nanotubes to the hydrochloric acid solution in step B1 is 6:70.

[0031] The weight ratio of the inhibitor, deionized water, and the halloysite nanotubes in step B1 in step B2 is 7:54:1, and the inhibitor is modified aluminum tripolyphosphate.

[0032] Preparation Example 6 This preparation example provides a halloysite nanotube-inhibitor composite, and its preparation method includes the following steps: B1. Add a hydrochloric acid solution with a concentration of 5 mol / L to halloysite nanotubes, heat and stir for 4 h under a water bath condition, centrifuge, filter, wash, and grind to obtain halloysite nanotubes etched with hydrochloric acid; B2. Mix the halloysite nanotubes etched with hydrochloric acid obtained in step B1, an inhibitor, and deionized water, ultrasonically disperse for 40 min, and then vacuum-dry the obtained suspension; B3. After the vacuum drying is completed, perform centrifugation to separate the solid phase, wash the solid phase, dry it, and grind it into powder to obtain the halloysite nanotube-inhibitor composite.

[0033] The weight ratio of the halloysite nanotubes to the hydrochloric acid solution in step B1 is 7:80.

[0034] The weight ratio of the inhibitor, deionized water, and the halloysite nanotubes in step B1 in step B2 is 8:60:1, and the inhibitor is modified aluminum tripolyphosphate. Example

[0035] An aqueous pre-coated primer includes component A and component B with a weight ratio of 8:1; Component A includes the following components in parts by weight: 50 parts of ethylene glycol monobutyl ether, 50 parts of aluminum powder, 15 parts of passivation aid, 400 parts of epoxy emulsion, 170 parts of deionized water, 8 parts of dispersant, 3 parts of defoamer, 250 parts of zinc iron powder, 115 parts of aqueous aluminum silver paste, 30 parts of zinc phosphate, 5 parts of bentonite, 5 parts of fumed silica, 3 parts of substrate wetting agent, 8 parts of anti-corrosion flash rust inhibitor, 3 parts of thickener; The epoxy emulsion is an acrylic acid-modified epoxy emulsion and an aqueous epoxy emulsion with a weight ratio of 0.1:1, and the acrylic acid-modified epoxy emulsion is prepared from Preparation Example 1; Component B is an epoxy curing agent, including an aqueous amine curing agent and water with a mass ratio of 4:1.

[0036] The aqueous pre-coated primer of this application is prepared by the following method, including the following steps: S1. Mix and disperse ethylene glycol monobutyl ether, aluminum powder, and passivation aid for 15 min to obtain mixture I, and let it stand for 24 h; S2. Mix mixture I and epoxy emulsion, and then add dispersant, defoamer, aqueous aluminum silver paste, substrate wetting agent, anti-corrosion flash rust inhibitor, and thickener and mix and disperse to obtain mixture II; S3. Mix and grind zinc iron powder, zinc phosphate, bentonite, and fumed silica until the fineness is ≤ 30 μm to obtain a mixture, and then mix and disperse the mixture with mixture II and deionized water to obtain component A; S4. Mix Component A and Component B to prepare the waterborne pre - coated primer. Example

[0037] The difference between this example and Example 1 is that Component A includes the following components in parts by weight: 40 parts of ethylene glycol monobutyl ether, 40 parts of aluminum powder, 10 parts of passivation aid, 350 parts of epoxy emulsion, 150 parts of deionized water, 5 parts of dispersant, 1 part of defoamer, 200 parts of zinc - iron powder, 100 parts of water - borne aluminum silver paste, 20 parts of zinc phosphate, 2 parts of bentonite, 2 parts of fumed silica, 1 part of substrate wetting agent, 5 parts of anti - flash rust agent, and 1 part of thickener. Example

[0038] The difference between this example and Example 1 is that Component A includes the following components in parts by weight: 60 parts of ethylene glycol monobutyl ether, 60 parts of aluminum powder, 20 parts of passivation aid, 450 parts of epoxy emulsion, 180 parts of deionized water, 10 parts of dispersant, 5 parts of defoamer, 300 parts of zinc - iron powder, 130 parts of water - borne aluminum silver paste, 40 parts of zinc phosphate, 8 parts of bentonite, 8 parts of fumed silica, 5 parts of substrate wetting agent, 12 parts of anti - flash rust agent, and 5 parts of thickener. Example

[0039] The difference between this example and Example 1 is that in this example, the epoxy emulsion is an acrylic - modified epoxy emulsion and a water - borne epoxy emulsion with a weight ratio of 0.3:1. Example

[0040] The difference between this example and Example 1 is that in this example, the epoxy emulsion is an acrylic - modified epoxy emulsion and a water - borne epoxy emulsion with a weight ratio of 0.6:1. Example

[0041] The difference between this example and Example 1 is that in this example, the epoxy emulsion is an acrylic - modified epoxy emulsion and a water - borne epoxy emulsion with a weight ratio of 0.8:1.

[0042] Comparative Example 1 The difference between this comparative example and Example 5 is that when preparing the water - borne pre - coated primer, the epoxy emulsion is only an acrylic - modified epoxy emulsion.

[0043] Comparative Example 2 The difference between this comparative example and Example 5 is that when preparing the water - borne pre - coated primer, the epoxy emulsion is only a water - borne epoxy emulsion. Example

[0044] The difference between Example 7 and Example 5 is that the acrylic - modified epoxy emulsion is prepared from Preparation Example 2. Example

[0045] The difference between Example 8 and Example 5 is that the acrylic - modified epoxy emulsion is prepared from Preparation Example 3. Example

[0046] The difference between Example 9 and Example 7 is that the component A further includes 20 parts by weight of halloysite nanotube-inhibitor complex prepared in Preparation Example 4. Example

[0047] The difference between Example 10 and Example 7 is that the component A further includes 32 parts by weight of halloysite nanotube-inhibitor complex prepared in Preparation Example 4. Example

[0048] The difference between Example 11 and Example 7 is that the component A further includes 40 parts by weight of halloysite nanotube-inhibitor complex prepared in Preparation Example 4. Example

[0049] The difference between Example 12 and Example 10 is that the halloysite nanotube-inhibitor complex is prepared in Preparation Example 5. Example

[0050] The difference between Example 13 and Example 10 is that the halloysite nanotube-inhibitor complex is prepared in Preparation Example 6.

[0051] Experimental detection The waterborne pre-coated primers prepared in Examples 1-13 and Comparative Examples 1-2 were subjected to performance detection in accordance with the standard Q / CR 581-2017.

[0052] Detection results The detection results are shown in Table 1 below.

[0053] Table 1 Cross-cut test (level) Flexural property (2mm) Surface drying time (min) Through drying time (min) Example 1 0 No cracks, no peeling 3 36 Example 2 0 No cracks, no peeling 4 41 Example 3 0 No cracks, no peeling 4 43 Example 4 0 No cracks, no peeling 4 34 Example 5 0 No cracks, no peeling 3 30 Example 6 0 No cracks, no peeling 3 33 Example 7 0 No cracks, no peeling 3 29 Example 8 0 No cracks, no peeling 3 31 Example 9 0 No cracks, no peeling 3 31 Example 10 0 No cracks, no peeling 3 27 Example 11 0 No cracks, no peeling 3 30 Example 12 0 No cracks, no peeling 3 25 Example 13 0 No cracks, no peeling 3 27 Comparative example 1 1 Cracks occurred, peeling occurred 8 65 Comparative example 2 1 Cracks occurred, peeling occurred 11 72 The waterborne pre-coated primers prepared in Examples 1-13 and Comparative Examples 1-2 were subjected to salt spray resistance performance detection and welding and cutting performance detection in accordance with the standard Q / CR 581-2017. The detection results show that the waterborne pre-coated primers prepared in this application can meet the requirements of 120h of neutral salt spray resistance, without blistering or rusting, the coating film damage or rust width at the scratch does not expand, and the adhesion does not decrease significantly when pried with a blade; there is no obstacle to welding arc starting, the weld formation is uniform and crack-free, and the coating film welding or cutting ablation width is less than 10mm.

[0054] Result analysis Combined with Examples 1-13, Comparative Examples 1-2 and Table 1, it can be seen that the waterborne pre-coated primer prepared in this application has excellent comprehensive performance. The waterborne pre-coated primer prepared in accordance with this application has strong covering power, good rust prevention performance, is easy to construct, has a fast drying speed, simplifies the construction process, and improves work efficiency. And during welding, it is heat-resistant and the paint layer will not melt, ensuring the welding performance of the metal surface.

[0055] The above are all preferred embodiments of the present application, and do not limit the protection scope of the present application. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application shall be covered within the protection scope of the present application.

Claims

1. An aqueous precoating primer, characterized in that, It includes component A and component B with a weight ratio of 8:1; The component A includes the following components in parts by weight: 40-60 parts of ethylene glycol monobutyl ether, 40-60 parts of aluminum powder, 10-20 parts of passivation assistant, 350-450 parts of epoxy emulsion, 150-180 parts of deionized water, 5-10 parts of dispersant, 1-5 parts of defoamer, 200-300 parts of zinc iron powder, 100-130 parts of water-based aluminum silver paste, 20-40 parts of zinc phosphate, 2-8 parts of bentonite, 2-8 parts of fumed silica, 1-5 parts of substrate wetting agent, 5-12 parts of anti-corrosion flash rust inhibitor, 1-5 parts of thickener; The component B is an epoxy curing agent.

2. The water-based pre-coated primer according to claim 1, characterized in that, The epoxy emulsion includes acrylic modified epoxy emulsion and water-based epoxy emulsion, and the weight ratio of the acrylic modified epoxy emulsion to the water-based epoxy emulsion is (0.1-0.8):

1.

3. The waterborne pre-coated primer according to claim 2, characterized in that, The preparation method of the acrylic modified epoxy emulsion includes the following steps: A1. Prepare materials according to 20-30 parts of epoxy resin E-20, 15-25 parts of ethylene glycol monobutyl ether, 15-25 parts of n-butanol, 5-8 parts of methacrylic acid, 5-8 parts of butyl acrylate, 5-10 parts of styrene, 1-2 parts of dibenzoyl peroxide, 5-8 parts of triethylamine, and 25-35 parts of deionized water in parts by weight; A2. Mix epoxy resin E-20, ethylene glycol monobutyl ether and n-butanol, heat and stir to raise the temperature to 110-120 °C to obtain a mixed solution I; A3. Drop methacrylic acid, butyl acrylate and styrene into the mixed solution prepared in step A1, then add dibenzoyl peroxide, and keep the temperature at 110-120 °C under nitrogen protection for 2.5-3 h to obtain a mixed solution II; A4. After cooling the mixed solution II to 50-55 °C, add triethylamine to neutralize and form a salt, keep the temperature for 0.5-1 h, then add deionized water, and disperse at a high speed of 2500-3000 rpm for 0.5-1 h to obtain the acrylic modified epoxy emulsion.

4. The waterborne precoating primer according to claim 1, wherein The component A also includes 20-40 parts by weight of halloysite nanotube-inhibitor composite.

5. The waterborne precoating primer according to claim 4, wherein The preparation method of the halloysite nanotube-inhibitor composite includes the following steps: B1. Add hydrochloric acid solution with a concentration of (3-5) mol / L to halloysite nanotubes, heat and stir under water bath conditions for 4-6 h, centrifuge, filter, wash and grind to obtain halloysite nanotubes etched with hydrochloric acid; B2. Mix the halloysite nanotubes etched with hydrochloric acid prepared in step B1, inhibitor and deionized water, ultrasonically disperse for 40-60 min, and then vacuum dry the obtained suspension; B3. After the vacuum drying is completed, perform centrifugation to separate the solid phase, wash the solid phase, dry it, and grind it into powder to obtain the halloysite nanotube-inhibitor composite.

6. The waterborne precoating primer according to claim 5, wherein The weight ratio of the halloysite nanotubes to the hydrochloric acid solution in step B1 is (5-7):(60-80).

7. The waterborne precoating primer according to claim 5, wherein The weight ratio of the inhibitor, deionized water in step B2 and the halloysite nanotubes in step B1 is (6-8):(50-60):

1.

8. The waterborne precoating primer according to claim 1, wherein, The epoxy curing agent includes a water-based amine curing agent and deionized water with a weight ratio of 4:

1.

9. The waterborne precoating primer according to claim 1, characterized in that, The passivation aid is zinc molybdate, the dispersant is fatty acid polyethylene glycol, the defoamer is polydimethylsiloxane, the anti-flooding and anti-rust agent is titanate coupling agent, the substrate wetting agent is sodium dodecyl sulfonate, and the thickener is ethoxy polyurethane polymer.

10. A method for preparing the waterborne precoating primer according to any one of claims 1-9, characterized in that, It includes the following steps: S1. Mix and disperse ethylene glycol monobutyl ether, aluminum powder and the passivation aid for 10 - 20 min to obtain mixture I, and let it stand for 22 - 24 h; S2. Mix mixture I and epoxy emulsion, then add the dispersant, defoamer, aqueous aluminum silver paste, substrate wetting agent, anti-flooding and anti-rust agent and thickener and mix and disperse to obtain mixture II; S3. Mix and grind zinc iron powder, zinc phosphate, bentonite and fumed silica until the fineness is ≤ 30 μm to obtain a mixed material, and then mix and disperse the mixed material with mixture II and deionized water to obtain component A; S4. Mix component A and component B to prepare the aqueous pre-coated primer.