Epoxy zinc-based polyester composite coating and preparation method thereof

Abstract

The invention relates to an epoxy zinc-based polyester composite coating and a preparation method thereof, and belongs to the technical field of powder coatings. The coating is formed by compounding a bottom-layer epoxy zinc-based coating and a surface-layer polyester coating, and the epoxy zinc-based coating is in contact with the surface of a steel substrate; the coating has the advantages of being good in corrosion resistance, capable of saving resources and environmentally friendly. The substrate is subjected to shot blasting and silane coupling treatment, so that the corrosion resistance of the coating is greatly improved; spraying an epoxy zinc-based powder coating on the surface of the treated matrix; curing until the surface of the coating flows to form a film by adopting an incomplete curing mode, so as to obtain an incompletely cured epoxy zinc-based coating; a polyester powder coating is sprayed on the epoxy zinc-based coating which is not completely cured; a complete curing mode is adopted to obtain a cured polyester coating, and the cured polyester coating is compounded with an epoxy zinc-based coating to form an epoxy zinc-based polyester composite coating; the epoxy zinc-based coating is combined with the polyester coating in an incomplete curing mode, physical embedding, physical adsorption, chemical adsorption and interaction of interlayer chemical bonds are included, the whole coating can be compounded into a whole, and more excellent physical and mechanical properties and corrosion resistance are achieved.

Description

Technical Field

[0001] The invention relates to an epoxy zinc-based polyester composite coating and a preparation method thereof, belonging to the technical field of powder coatings. Background Art

[0002] Corrosion is the main cause of failure of metal steel components and has always been a problem worthy of everyone's attention. At present, in order to prevent the adverse effects of corrosion on metal steel components, hot-dip galvanized polyester composite coatings and hot-dip galvanized plastic composite coatings have been widely used in metal steel components. This type of anti-corrosion form has good corrosion resistance, weather resistance and aging resistance, and good mechanical strength, which effectively extends the service life of steel components.

[0003] However, the hot-dip galvanizing process temperature of hot-dip galvanized polyester composite coating and hot-dip galvanized plastic composite coating in the production process is generally around 450°C, which has high energy consumption. The galvanizing process will produce residual liquid and wastewater such as immersion plating waste gas, plating assistant solution, passivation solution, etc., which pollute the environment. In addition, during use, zinc corrodes and oxidizes and enters the environment, causing secondary pollution. Summary of the invention

[0004] In order to overcome the defects of the prior art, one of the purposes of the present invention is to provide an epoxy zinc-based polyester composite coating, which has good anti-corrosion performance and is resource-saving and environmentally friendly.

[0005] The second purpose of the present invention is to provide a method for preparing an epoxy zinc-based polyester composite coating, which greatly improves the corrosion resistance of the coating by pre-treating the substrate; the epoxy zinc-based coating is combined with the polyester coating in an incompletely cured manner, which not only includes physical embedding, physical adsorption, and chemical adsorption, but also the interaction of interlayer chemical bonds, so that the entire coating can be composited into one, and has more excellent physical and mechanical properties and corrosion resistance.

[0006] To achieve the purpose of the present invention, the following technical solutions are provided.

[0007] An epoxy zinc-based polyester composite coating, wherein the coating is composited by a bottom epoxy zinc-based coating and a surface polyester coating, and the epoxy zinc-based coating is in contact with the surface of the substrate;

[0008] The substrate is made of steel;

[0009] Preferably, the thickness of the epoxy zinc-based coating is 36 μm to 56 μm;

[0010] The polyester coating preferably has a thickness of 70 μm to 90 μm.

[0011] The epoxy zinc-based coating is prepared by using epoxy zinc-based powder coating in the prior art. Preferably, taking the raw material of the epoxy zinc-based powder coating as 100%, the components and their mass fractions are as follows:

[0012]

[0013] The preferred epoxy resin is bisphenol A epoxy resin E12.

[0014] The curing agent is a curing agent for epoxy resin, preferably HYH251 produced by Anhui Hengyuan New Materials Co., Ltd.

[0015] The curing accelerator is a curing accelerator for epoxy resin, preferably HYC-02 produced by Anhui Hengyuan New Materials Co., Ltd.

[0016] The leveling agent is a leveling agent commonly used in the prior art of powder coatings in the art, and is preferably acrylic polyester.

[0017] The toughening agent is a flexibility aid, which is a toughening agent commonly used in the prior art of powder coatings in the field, and is preferably polyvinyl butyral (PVB).

[0018] The degassing agent is a smooth degassing agent, which is a degassing agent commonly used in the prior art of powder coatings in this field, and is preferably BYK961 produced by BYK Chemicals of Germany.

[0019] A preferred flow promoter is fumed silica.

[0020] The zinc powder is flaky zinc powder or spherical zinc powder, preferably flaky zinc powder 4018 produced by Hunan Xinweiling Metal New Materials Technology Co., Ltd.

[0021] The filler is a filler commonly used in the prior art of powder coatings in the art, and is preferably precipitated barium sulfate.

[0022] The preparation method of epoxy zinc-based powder coating is as follows:

[0023] The various components of the raw materials are fully dry-mixed and then added to the extruder. The screw temperature is controlled at 100°C to 110°C for extrusion. The powder coating is then crushed, graded and sieved according to the required particle size to obtain the epoxy zinc-based powder coating.

[0024] The polyester coating is prepared by using polyester powder coating in the prior art. Preferably, taking the raw material of the polyester powder coating as 100%, the components and mass fractions are as follows:

[0025]

[0026] The preferred polyester resin is P5706-2 produced by Yantai Longcai New Materials Co., Ltd.

[0027] The curing agent is a curing agent for polyester resin, preferably triglycidyl isocyanurate (TGIC).

[0028] The leveling agent is a leveling agent commonly used in the prior art of powder coatings in the art, and is preferably acrylic polyester.

[0029] The toughening agent is a flexibility aid, which is a conventional toughening agent used in the prior art of powder coatings in this field, and is preferably F-104 produced by Suzhou Patna Environmental Protection New Materials Co., Ltd.

[0030] The degassing agent is a smooth degassing agent, which is a degassing agent commonly used in the prior art of powder coatings in this field, and is preferably BYK961 produced by BYK Chemicals of Germany.

[0031] The pigment and filler are a combination of pigments and fillers conventionally used in the prior art of powder coatings in this field. The pigment is a combination of a pigment of a desired color and titanium white. The pigment of the desired color includes one or more of carbon black, phthalocyanine green and iron oxide yellow. The filler is precipitated barium sulfate.

[0032] The preparation method of polyester powder coating is as follows:

[0033] The various components of the raw materials are fully dry-mixed and then added to the extruder. The screw temperature is controlled at 100°C to 110°C for extrusion. The powder coating is then crushed, graded and sieved according to the required particle size to obtain the polyester powder coating.

[0034] A method for preparing the epoxy zinc-based polyester composite coating of the present invention, the method steps are as follows:

[0035] (1) Substrate pretreatment

[0036] The substrate pretreatment adopts a combination of physical and chemical pretreatment, namely shot blasting and silane coupling treatment. First, a uniform and dense abrasive layer is formed on the substrate surface through the high-speed jet flow generated by the shot blasting equipment, thereby removing impurities such as depressions, scale, rust, and oil stains on the substrate surface; then the substrate after shot blasting is dusted, degreased, washed with water, and immersed in a silane coupling agent aqueous solution for surface silanization treatment, and the treated substrate is obtained after drying.

[0037] Specifically, the surface silanization treatment is performed by immersing the substrate in an aqueous solution of a silane coupling agent at room temperature for 3 to 5 minutes.

[0038] Preferably, the mass fraction of the silane coupling agent is 8%, based on the total mass of the silane coupling agent aqueous solution being 100%; further, preferably, the silane coupling agent is AB-A8 produced by Beijing Anbang Star Technology Co., Ltd.

[0039] (2) Epoxy zinc-based powder coating spraying

[0040] The epoxy zinc-based powder coating is sprayed on the treated substrate surface, preferably by electrostatic spraying.

[0041] (3) Curing of epoxy zinc-based coating

[0042] The epoxy zinc-based coating is cured by an incomplete curing method, that is, it is cured at 200° C. to 230° C. until the coating surface flows and forms a film, thereby obtaining an incompletely cured epoxy zinc-based coating.

[0043] The preferred curing time is 3 to 5 minutes.

[0044] (4) Polyester powder coating spraying

[0045] The polyester powder coating is sprayed onto the uncured epoxy zinc-based coating, preferably by electrostatic spraying.

[0046] (5) Polyester coating curing

[0047] The polyester coating is cured by a complete curing method, that is, cured at 200° C. to 230° C. for 9 min to 15 min to obtain a cured polyester coating, which is composited with the epoxy zinc-based coating to form the epoxy zinc-based polyester composite coating of the present invention.

[0048] Beneficial Effects

[0049] (1) The present invention provides an epoxy zinc-based polyester composite coating, wherein the coating uses an epoxy zinc base layer as a bottom coating to replace hot-dip galvanizing, thereby greatly reducing energy consumption; and uses a polyester layer as a surface coating to make up for the disadvantage of insufficient UV resistance of the epoxy system, and has outstanding corrosion resistance.

[0050] (2) The present invention provides a method for preparing an epoxy zinc-based polyester composite coating, wherein the substrate pretreatment in the method adopts shot blasting and silane coupling treatment, which is environmentally friendly and pollution-free;

[0051] The anchor structure formed by shot blasting causes the active epoxy groups in the epoxy zinc-based powder to react with the free bonds on the metal surface to form a strong chemical bond; the silane in the silane treatment liquid is rapidly adsorbed to the substrate surface after hydrolysis to form a stable film layer, which is beneficial to the wetting and spreading of the coating during curing. The substrate surface after silanization treatment has abundant active siloxane bonds, which can react chemically with the active groups in the epoxy zinc-based powder to form a polymer network structure, greatly improving the corrosion resistance of the coating.

[0052] (3) The present invention provides a method for preparing an epoxy zinc-based polyester composite coating, in which electrostatic spraying is used instead of traditional hot-dip plating, and the high temperature required for molten zinc ingots is eliminated, thereby reducing heat loss and reducing the emission of waste gas and waste liquid.

[0053] (4) The present invention provides a method for preparing an epoxy zinc-based polyester composite coating, wherein the epoxy zinc-based coating is cured by an incomplete curing method, which not only saves energy and reduces heat energy loss by more than 65%, but also makes the combination of the epoxy zinc-based coating and the polyester coating include not only physical intercalation, physical adsorption, and chemical adsorption, but also the interaction of interlayer chemical bonds, so that the two are composited into one, and have more excellent physical and mechanical properties and corrosion resistance; it can also shorten the curing time to 1 / 3 of the curing time of the prior art; in addition, by utilizing the residual temperature of the epoxy zinc base layer during curing to spray the polyester powder coating, the powder coating rate of the polyester powder coating can be increased by 10%, thereby reducing the production cost.

[0054] (5) The present invention provides a method for preparing an epoxy zinc-based polyester composite coating, which achieves almost zero pollution and reduces carbon emissions, and has very important economic and social benefits for building a resource-saving and environmentally friendly transportation industry. DETAILED DESCRIPTION

[0055] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0056] In the following embodiments:

[0057] Raw materials for epoxy zinc-based powder coatings:

[0058] The epoxy resin is bisphenol A epoxy resin E12,

[0059] The curing agent is epoxy resin curing agent, HYH251 produced by Anhui Hengyuan New Materials Co., Ltd.

[0060] The curing accelerator is a curing accelerator for epoxy resin, which is HYC-02 produced by Anhui Hengyuan New Materials Co., Ltd.

[0061] The leveling agent is acrylic polyester.

[0062] The toughening agent is polyvinyl butyral.

[0063] The degassing agent is BYK961 produced by BYK Chemicals of Germany.

[0064] The flow promoter is fumed silica.

[0065] The zinc powder is flaky zinc powder 4018 produced by Hunan Xinweiling Metal New Materials Technology Co., Ltd.

[0066] The filler is precipitated barium sulfate.

[0067] Raw materials for polyester powder coatings:

[0068] The polyester resin is P5706-2 produced by Yantai Longcai New Materials Co., Ltd.

[0069] The curing agent is triglycidyl isocyanurate.

[0070] The leveling agent is acrylic polyester.

[0071] The toughening agent is F-104 produced by Suzhou Patna Environmental Protection New Materials Co., Ltd.

[0072] The degassing agent is BYK961 produced by BYK Chemicals of Germany.

[0073] The pigment and filler are a combination of pigment and filler. Taking the raw material of polyester powder coating as 100%, the composition and mass fraction of the pigment are: titanium dioxide 1.2%, iron oxide yellow 1%, phthalocyanine green 2%; the filler is precipitated barium sulfate.

[0074] In the silane coupling agent aqueous solution, the silane coupling agent is AB-A8 produced by Beijing Anbang Star Technology Co., Ltd., and the mass fraction of the silane coupling agent is 8% based on the total mass of the silane coupling agent aqueous solution as 100%.

[0075] Example 1

[0076] The invention discloses an epoxy zinc-based polyester composite coating, which is composited by a bottom epoxy zinc-based coating and a surface polyester coating, and the epoxy zinc-based coating is in contact with the surface of a substrate.

[0077] The epoxy zinc-based coating is prepared by epoxy zinc-based powder coating. Taking the raw material of epoxy zinc-based powder coating as 100%, the components and their mass fractions are as follows:

[0078]

[0079] The preparation method of epoxy zinc-based powder coating is as follows:

[0080] The various components of the raw materials are fully dry-mixed and then added to the extruder. The screw temperature is controlled at 100°C to 110°C for extrusion. The powder coating is then crushed, graded and sieved according to the required particle size to obtain an epoxy zinc-based powder coating with a particle size of 40μm to 45μm.

[0081] The polyester coating is prepared by polyester powder coating. Taking the raw material of polyester powder coating as 100%, the components and mass fractions are as follows:

[0082]

[0083] The preparation method of polyester powder coating is as follows:

[0084] The various components of the raw materials are fully dry-mixed and then added to the extruder. The screw temperature is controlled at 100°C to 110°C for extrusion. Then, the powder coating is crushed, graded and sieved according to the required particle size to obtain a polyester powder coating with a particle size of 40μm to 45μm.

[0085] A method for preparing the epoxy zinc-based polyester composite coating described in this embodiment, the method steps are as follows:

[0086] (1) Substrate pretreatment

[0087] The substrate is a steel substrate. First, a high-speed jet stream generated by the shot blasting equipment forms a uniform and dense abrasive layer on the surface of the substrate, thereby removing impurities such as depressions, scale, rust, and oil stains on the surface of the substrate. Then, the substrate after shot blasting is dusted, degreased, washed, and immersed in a silane coupling agent aqueous solution at room temperature for 3 minutes for surface silanization treatment, and then dried to obtain the treated substrate.

[0088] (2) Epoxy zinc-based powder coating spraying

[0089] Electrostatically spraying epoxy zinc-based powder coating on the treated substrate surface;

[0090] (3) Curing of epoxy zinc-based coating

[0091] The epoxy zinc-based coating was cured by an incomplete curing method, that is, curing at 200°C for 3 minutes until the coating surface flowed and formed a film, thereby obtaining an incompletely cured epoxy zinc-based coating with a thickness of 36 μm to 56 μm.

[0092] (4) Polyester powder coating spraying

[0093] Using the residual heat of the epoxy zinc base during curing, the polyester powder coating is electrostatically sprayed on the uncured epoxy zinc base coating;

[0094] (5) Polyester coating curing

[0095] The polyester coating is cured by a complete curing method, that is, cured at 200° C. for 9 minutes to obtain a polyester coating with a thickness of 70 μm to 90 μm; the polyester coating is composited with the epoxy zinc-based coating to obtain an epoxy zinc-based polyester composite coating.

[0096] Example 2

[0097] The invention discloses an epoxy zinc-based polyester composite coating, which is composited by a bottom epoxy zinc-based coating and a surface polyester coating, and the epoxy zinc-based coating is in contact with the surface of a substrate.

[0098] The epoxy zinc-based coating is prepared by epoxy zinc-based powder coating. Taking the raw material of epoxy zinc-based powder coating as 100%, the components and their mass fractions are as follows:

[0099]

[0100] The preparation method of epoxy zinc-based powder coating is as follows:

[0101] The various components of the raw materials are fully dry-mixed and then added to the extruder. The screw temperature is controlled at 100°C to 110°C for extrusion. The powder coating is then crushed, graded and sieved according to the required particle size to obtain an epoxy zinc-based powder coating with a particle size of 40μm to 45μm.

[0102] The polyester coating is prepared by polyester powder coating. Taking the raw material of polyester powder coating as 100%, the components and mass fractions are as follows:

[0103]

[0104] The preparation method of polyester powder coating is as follows:

[0105] The various components of the raw materials are fully dry-mixed and then added to the extruder. The screw temperature is controlled at 100°C to 110°C for extrusion. Then, the powder coating is crushed, graded and sieved according to the required particle size to obtain a polyester powder coating with a particle size of 40μm to 45μm.

[0106] A method for preparing the epoxy zinc-based polyester composite coating described in this embodiment, the method steps are as follows:

[0107] (1) Substrate pretreatment

[0108] The substrate is a steel substrate. First, a high-speed jet stream generated by the shot blasting equipment forms a uniform and dense abrasive layer on the surface of the substrate, thereby removing impurities such as depressions, scale, rust, and oil stains on the surface of the substrate. Then, the substrate after shot blasting is dusted, degreased, washed, and immersed in a silane coupling agent aqueous solution at room temperature for 5 minutes for surface silanization treatment, and then dried to obtain the treated substrate.

[0109] (2) Epoxy zinc-based powder coating spraying

[0110] Electrostatically spraying epoxy zinc-based powder coating on the treated substrate surface;

[0111] (3) Curing of epoxy zinc-based coating

[0112] The epoxy zinc-based coating was cured by an incomplete curing method, that is, curing at 230°C for 5 minutes until the coating surface flowed and formed a film, thereby obtaining an incompletely cured epoxy zinc-based coating with a thickness of 36 μm to 56 μm.

[0113] (4) Polyester powder coating spraying

[0114] Using the residual heat of the epoxy zinc base during curing, the polyester powder coating is electrostatically sprayed on the uncured epoxy zinc base coating;

[0115] (5) Polyester coating curing

[0116] The polyester coating is cured by a complete curing method, that is, cured at 230° C. for 15 minutes to obtain a polyester coating with a thickness of 70 μm to 90 μm; the polyester coating is composited with the epoxy zinc-based coating to obtain an epoxy zinc-based polyester composite coating.

[0117] Example 3

[0118] The invention discloses an epoxy zinc-based polyester composite coating, which is composited by a bottom epoxy zinc-based coating and a surface polyester coating, and the epoxy zinc-based coating is in contact with the surface of a substrate.

[0119] The epoxy zinc-based coating is prepared by epoxy zinc-based powder coating. Taking the raw material of epoxy zinc-based powder coating as 100%, the components and their mass fractions are as follows:

[0120]

[0121]

[0122] The preparation method of epoxy zinc-based powder coating is as follows:

[0123] The various components of the raw materials are fully dry-mixed and then added to the extruder. The screw temperature is controlled at 100°C to 110°C for extrusion. The powder coating is then crushed, graded and sieved according to the required particle size to obtain an epoxy zinc-based powder coating with a particle size of 40μm to 45μm.

[0124] The polyester coating is prepared by polyester powder coating. Taking the raw material of polyester powder coating as 100%, the components and mass fractions are as follows:

[0125]

[0126] The preparation method of polyester powder coating is as follows:

[0127] The various components of the raw materials are fully dry-mixed and then added to the extruder. The screw temperature is controlled at 100°C to 110°C for extrusion. Then, the powder coating is crushed, graded and sieved according to the required particle size to obtain a polyester powder coating with a particle size of 40μm to 45μm.

[0128] A method for preparing the epoxy zinc-based polyester composite coating described in this embodiment, the method steps are as follows:

[0129] (1) Substrate pretreatment

[0130] The substrate is a steel substrate. First, a high-speed jet stream generated by the shot blasting equipment forms a uniform and dense abrasive layer on the surface of the substrate, thereby removing impurities such as depressions, scale, rust, and oil stains on the surface of the substrate. Then, the substrate after shot blasting is dusted, degreased, washed, and immersed in a silane coupling agent aqueous solution at room temperature for 4 minutes for surface silanization treatment, and then dried to obtain the treated substrate.

[0131] (2) Epoxy zinc-based powder coating spraying

[0132] Electrostatically spraying epoxy zinc-based powder coating on the treated substrate surface;

[0133] (3) Curing of epoxy zinc-based coating

[0134] The epoxy zinc-based coating was cured by an incomplete curing method, that is, curing at 200°C for 5 minutes until the coating surface flowed and formed a film, thereby obtaining an incompletely cured epoxy zinc-based coating with a thickness of 36 μm to 56 μm.

[0135] (4) Polyester powder coating spraying

[0136] Using the residual heat of the epoxy zinc base during curing, the polyester powder coating is electrostatically sprayed on the uncured epoxy zinc base coating;

[0137] (5) Polyester coating curing

[0138] The polyester coating is cured by a complete curing method, that is, cured at 230° C. for 9 minutes to obtain a polyester coating with a thickness of 70 μm to 90 μm; the polyester coating is compounded with the epoxy zinc-based coating to obtain an epoxy zinc-based polyester composite coating.

[0139] Performance Testing:

[0140] Performance test results of Examples 1 to 3

[0141]

[0142] The test results show that the coating surface is flat and smooth, the coating adhesion is level 0, the impact strength is ≥95kg×cm, there is no crack when the ф3 cylindrical axis is bent, and the coating shows excellent physical and mechanical properties; the cyclic salt spray resistance time is ≥2250h, and the coating shows excellent corrosion resistance.

Claims

1. An epoxy zinc-based polyester composite coating, characterized in that: The coating is composited by a bottom epoxy zinc-based coating and a surface polyester coating, and the epoxy zinc-based coating is in contact with the surface of the substrate; The substrate is made of steel; The epoxy zinc-based coating is prepared by using epoxy zinc-based powder coating; The polyester coating is prepared by using polyester powder coating.

2. The epoxy zinc-based polyester composite coating according to claim 1, characterized in that: The thickness of the epoxy zinc-based coating is 36 μm to 56 μm; the thickness of the polyester coating is 70 μm to 90 μm.

3. An epoxy zinc-based polyester composite coating according to claim 1 or 2, characterized in that: Taking the raw materials of epoxy zinc-based powder coating as 100%, the components and their mass fractions are as follows:

4. The epoxy zinc-based polyester composite coating according to claim 3, characterized in that: The epoxy resin is bisphenol A epoxy resin E12, The curing agent is a curing agent for epoxy resin, The curing accelerator is a curing accelerator for epoxy resin. The leveling agent is acrylic polyester. The toughening agent is polyvinyl butyral. The flow promoter is fumed silica. Zinc powder is flaky zinc powder or spherical zinc powder. The filler is precipitated barium sulfate.

5. The epoxy zinc-based polyester composite coating according to claim 4, characterized in that: The curing agent is HYH251 produced by Anhui Hengyuan New Materials Co., Ltd. The curing accelerator is HYC-02 produced by Anhui Hengyuan New Materials Co., Ltd. The degassing agent is BYK961 produced by BYK Chemicals of Germany. The zinc powder is flaky zinc powder 4018 produced by Hunan Xinweiling Metal New Materials Technology Co., Ltd.

6. The epoxy zinc-based polyester composite coating according to claim 1 or 2, characterized in that: Taking the raw material of polyester powder coating as 100%, the components and mass fractions are as follows:

7. The epoxy zinc-based polyester composite coating according to claim 6, characterized in that: The curing agent is a curing agent for polyester resin, The leveling agent is acrylic polyester. The color filler is a combination of a pigment and a filler. The pigment is a combination of a pigment of a desired color and titanium dioxide; the filler is precipitated barium sulfate.

8. The epoxy zinc-based polyester composite coating according to claim 7, characterized in that: The polyester resin is P5706-2 produced by Yantai Longcai New Materials Co., Ltd. The curing agent is triglycidyl isocyanurate. The toughening agent is F-104 produced by Suzhou Patna Environmental Protection New Materials Co., Ltd. The degassing agent is BYK961 produced by BYK Chemicals of Germany. The pigment is a combination of one or more of carbon black, phthalocyanine green and yellow iron oxide and titanium white.

9. A method for preparing the epoxy zinc-based polyester composite coating according to any one of claims 1 to 8, characterized in that: (1) Substrate pretreatment The substrate is first shot blasted and then silane coupling treated: First, a high-speed jet stream generated by the shot blasting equipment forms a uniform and dense abrasive layer on the surface of the substrate, thereby removing impurities such as depressions, scale, rust, and oil stains on the surface of the substrate; then the substrate after shot blasting is dusted, degreased, washed with water, and immersed in a silane coupling agent aqueous solution for surface silanization treatment, and then dried to obtain the treated substrate; (2) Epoxy zinc-based powder coating spraying spraying epoxy zinc-based powder coating on the treated substrate surface; (3) Curing of epoxy zinc-based coating The epoxy zinc-based coating is cured by an incomplete curing method, which is cured until the coating surface flows and forms a film, thereby obtaining an incompletely cured epoxy zinc-based coating. (4) Polyester powder coating spraying Spraying polyester powder coating over the uncured epoxy zinc-based coating; (5) Polyester coating curing A fully curing method is adopted to obtain a cured polyester coating, which is compounded with the epoxy zinc-based coating to form an epoxy zinc-based polyester composite coating.

10. The method for preparing an epoxy zinc-based polyester composite coating according to claim 9, characterized in that: In step (1), the surface silanization treatment is performed by immersing the surface in an aqueous solution of a silane coupling agent for 3 to 5 minutes at room temperature; the mass fraction of the silane coupling agent is 8% based on the total mass of the aqueous solution of the silane coupling agent as 100%; the silane coupling agent is AB-A8 produced by Beijing Anbang Star Technology Co., Ltd.; In step (2), the spraying method is electrostatic spraying; In step (3), curing at 200° C. to 230° C. for 3 to 5 minutes until the coating surface flows and forms a film, thereby obtaining an incompletely cured epoxy zinc-based coating; In step (4), the spraying method is electrostatic spraying; In step (5), curing is performed at 200° C. to 230° C. for 9 min to 15 min to obtain a cured polyester coating.

Images