An electrostatic powder spray process

Abstract

The application relates to an electrostatic powder spraying process and relates to the field of surface coating processes. The electrostatic powder spraying process comprises the steps of aluminum material pretreatment, aluminum material surface treatment, aluminum material suspension, electrostatic spraying, solidification and unloading detection, and raw material powder comprises thermosetting epoxy resin, polyurethane resin, a curing agent, a dispersing agent, pigments, graphene oxide and precipitated barium sulfate. The application has the effect of improving the adhesion of the powder coating and the aluminum material.

Description

Technical Field

[0001] This invention relates to the field of surface coating processes, and in particular to an electrostatic powder spraying process. Background Technology

[0002] The purpose of powder coating is to form a uniform, wear-resistant, corrosion-resistant, and aesthetically pleasing coating on the surface of an object. This coating has high durability and corrosion resistance, protecting the object's surface from external environmental erosion and damage, thus extending the object's lifespan. Furthermore, powder coating can achieve a variety of colors and effects to meet diverse aesthetic needs. Powder coating is widely used in industries such as furniture, automobiles, construction, and electrical appliances.

[0003] Electrostatic powder coating is a coating process that uses an electrostatic powder spray gun to spray paint, which disperses the powder particles and gives them a negative charge. These charged particles are then attracted to a grounded substrate by airflow (or centrifugal force, etc.) and electrostatic attraction, and are subsequently heated to melt and solidify into a film. Electrostatic powder coating is a relatively new coating technology that has developed rapidly in recent decades.

[0004] Electrostatic powder coating of aluminum surfaces can produce aluminum materials with a wide range of colors and meet requirements for corrosion resistance, wear resistance, and other properties. However, in current electrostatic powder coating processes, the adhesion between the coating and the aluminum material is not strong, and some coatings are prone to peeling off during use. Summary of the Invention

[0005] To improve the adhesion between the coating and the aluminum material, this application provides an electrostatic powder coating process.

[0006] The electrostatic powder coating process provided in this application adopts the following technical solution: An electrostatic powder coating process includes the following steps: S1 Aluminum Material Pretreatment: Grinding and finishing the aluminum material to make the surface smooth; S2 Aluminum Surface Treatment: Aluminum is surface treated using chemical methods to remove the oxide film on the aluminum surface and generate a phosphate film on the aluminum surface. S3 Suspended Aluminum Material: Transfer the surface-treated aluminum material into the powder coating booth, align the decorative surface with the electrostatic spray gun and suspend it, keeping the distance between the aluminum material and the electrostatic spray gun at 100-120mm. S4 electrostatic spraying: Using an electrostatic spray gun to spray raw material powder onto the surface of aluminum to form a powder coating. The raw material powder includes: thermosetting epoxy resin, polyurethane resin, curing agent, dispersant, pigment, graphene oxide and precipitated barium sulfate. S5 Curing: The sprayed aluminum material is sent into the curing oven, the heating temperature is set to 160-200℃, and the curing time is 15-25min; S6 Material Inspection: After the cured aluminum material is removed and cooled to room temperature, the powder coating is inspected.

[0007] By adopting the above technical solutions, the aluminum material is pre-treated to create a smooth surface through the formation of a phosphate film, which facilitates coating adhesion. The coating formulation is improved to enhance adhesion between the coating and the aluminum material. The addition of graphene oxide imparts a negative charge to the powder, which is more conducive to adhesion to positively charged aluminum during electrostatic spraying. The compounding of thermosetting epoxy resin, polyurethane resin, and curing agent improves the corrosion resistance and aging resistance of the powder coating. Dispersants and precipitated barium sulfate improve powder flowability, making the powder easier to spray and disperse evenly on the aluminum surface to form a film.

[0008] Optionally, the raw material powder includes: 65-80 parts of thermosetting epoxy resin; 25-35 parts of polyurethane resin; 50-70 parts of curing agent; 3-6 parts dispersant; 10-25 parts pigment; 10-15 parts of graphene oxide; 8-12 parts of barium sulfate by precipitation method.

[0009] By adopting the above technical solution and using a specific component ratio, the prepared powder coating has good adhesion to the aluminum surface, the coating is not easy to fall off, and the corrosion resistance and aging resistance of the powder coating are enhanced, providing good protection for the aluminum.

[0010] Optionally, step S2 specifically includes the following steps: S2a: The pre-treated aluminum surface is subjected to two liquid sandblasting treatments, with abrasive particle sizes of 0.5mm and 1mm respectively. The first sandblasting treatment lasts for 30 seconds, and the second sandblasting treatment lasts for 10 seconds. The included angle between the sandblasting directions of the two sandblasting treatments is 70-100°. S2b: Use degreasing solution to degrease the surface of the sandblasted aluminum material; S2c: Rinse the degreased aluminum material with clean water, and use colloidal titanium to adjust the surface of the aluminum material; S2d: Phosphating treatment is performed on the rinsed aluminum material using phosphating solution to form a phosphating film on the aluminum material surface; S2e: Phosphated aluminum materials are cleaned a second time with deionized water; S2f: Pre-dry the cleaned aluminum material at a temperature of 120-140℃.

[0011] By adopting the above technical solution, the oxide film and oil stains on the surface of aluminum are removed by sandblasting, degreasing and multiple water washing. A phosphate film is formed on the surface of aluminum by surface conditioning and phosphate treatment. The phosphate film enhances the corrosion resistance and adhesion of the aluminum surface.

[0012] Optionally, in step S2d, the selected phosphating solution is composed of the following raw materials: H3PO4 21-25g / L; NaF 4-6g / L; (NH4)2MoO4 0.6-0.9 g / L; FeO 1-3g / L; ZnNO3 14-18g / L.

[0013] By adopting the above technical solution, using a zinc-based phosphating solution, and adding (NH4)2MoO4 as a promoter to catalyze the phosphating reaction, the quality of the phosphating film is improved. Fe is also added. 2+ It also helps with the phosphating of aluminum, improving the uniformity and density of the prepared phosphating film, which can completely cover the surface of the aluminum and further enhance its corrosion resistance.

[0014] Optionally, in step S2d, the process parameters for phosphating are: free acidity 0.7-1.5; total acidity 22-27; phosphating temperature 40-50℃; phosphating time 5-10min.

[0015] By adopting the above technical solution, the speed of phosphating film formation and the thickness of the phosphating film can be controlled by controlling the free acidity, total acidity, phosphating time and phosphating temperature, and the corrosion resistance of the phosphating film is enhanced.

[0016] Optionally, in step S2b, the selected oiling fluid includes the following components: H3PO4 15-18 g / L, OP-10 emulsifier 4-8 g / L.

[0017] Optionally, in step S4, the spraying process parameters are: the spraying pressure of the electrostatic spray gun is set to 0.15-0.25MPa, the voltage is 110-135kV, and the current is 50-70uA.

[0018] By adopting the above technical solution, the amount of powder applied can be controlled by controlling the spraying process, the thickness of the powder coating can be controlled, and the spraying effect is good.

[0019] Optionally, the curing agent is triglycidyl isocyanurate.

[0020] Optionally, the dispersant may be sodium tripolyphosphate.

[0021] Optionally, in step S4, the thickness of the powder coating is controlled to be 65-90 μm.

[0022] In summary, this application has the following beneficial effects: 1. Pre-treatment of the aluminum surface, through the formation of a phosphate film, ensures a smooth surface and facilitates coating adhesion. Improving the coating formulation enhances adhesion between the coating and the aluminum. Adding graphene oxide imparts a negative charge to the powder, which is more conducive to adhesion to positively charged aluminum during electrostatic spraying. The resulting coating exhibits high bonding strength with the aluminum body. The compounding of thermosetting epoxy resin, polyurethane resin, and curing agent improves the corrosion and aging resistance of the powder coating. Dispersants and precipitated barium sulfate improve powder flowability, making the powder easier to spray and disperse evenly on the aluminum surface to form a film.

[0023] 2. By using a specific ratio of components, the prepared powder coating has good adhesion to the aluminum surface, the coating is not easy to fall off, and the corrosion resistance and aging resistance of the powder coating are enhanced, providing good protection for the aluminum.

[0024] 3. A zinc-based phosphating solution is used, with (NH4)2MoO4 added as a promoter to catalyze the phosphating reaction and improve the quality of the phosphating film. Fe is also added. 2+ It also helps with the phosphating of aluminum, improving the uniformity and density of the prepared phosphating film and further enhancing its corrosion resistance. Detailed Implementation

[0025] The present application will be further described in detail below with reference to Examples 1-3.

[0026] This application discloses an electrostatic powder coating process. When performing electrostatic powder coating, a complete coating production line can be used, which consists of pretreatment equipment, water drying equipment, electrostatic powder spraying and recovery equipment, powder curing equipment, and overhead conveying equipment.

[0027] Example 1 An electrostatic powder coating process includes the following steps: S1 Aluminum Material Pretreatment: Prepare the aluminum material to be sprayed, and grind and trim the aluminum material using 240# sandpaper to make the surface of the aluminum material to be sprayed smooth.

[0028] S2 Aluminum Surface Treatment: This involves using chemical methods to treat the surface of aluminum, specifically including the following steps: S2a: The polished aluminum material is then sandblasted twice. The first sandblasting uses 0.5mm abrasive particles for 30 seconds, and the second sandblasting uses 1mm abrasive particles for 10 seconds. The angle between the sandblasting directions for the two sandblasting processes is set to 70°. Sandblasting removes dirt and impurities from the aluminum surface, eliminates surface unevenness, and creates a certain degree of roughness.

[0029] S2b: Prepare a degreasing solution, which includes 15g / L of H3PO4 and 4g / L of OP-10 emulsifier. The aluminum surface is degreased by the degreasing solution, and the oxide film on the aluminum surface can be removed by reacting with the degreasing solution.

[0030] S2c: Rinse the degreased aluminum material with clean water for 2 minutes, and then perform surface conditioning on the aluminum material. Colloidal titanium is used for surface conditioning, which changes the properties of the aluminum material surface and makes it more active.

[0031] S2d: Prepare a zinc-based phosphating solution and use it to phosphate aluminum materials, so that a phosphating film is formed on the surface of the aluminum materials. The phosphating film enhances the corrosion resistance of the aluminum materials and also enhances the adhesion of the aluminum materials surface.

[0032] The phosphating solution was formulated with 21 g / L H3PO4, 4 g / L NaF, 0.6 g / L (NH4)2MoO4, 1 g / L FeO, and 14 g / L ZnNO3.

[0033] The phosphating solution is prepared by the following steps: add 85% H3PO4 to a beaker, dilute with distilled water, weigh out ZnNO3 and FeO accordingly, stir with a magnetic stirrer until completely dissolved, then add NaF and (NH4)2MoO4 accelerator, stir until the solution is clear, measure the pH and adjust with NaOH solution to pH=4.5.

[0034] The prepared phosphating solution has a free acidity of 1.5 and a total acidity of 24. The aluminum material is treated at 40°C for 5 minutes, and the resulting phosphating film is dense and completely covers the surface of the aluminum material.

[0035] S2e: Perform a second cleaning on the phosphated aluminum material, using deionized water for 3 minutes.

[0036] S2f: Pre-dry the cleaned aluminum material by placing it in a drying oven, setting the drying temperature to 120℃, and removing it after 3 minutes of drying.

[0037] S3 Suspended Aluminum Material: The surface-treated aluminum material is transported to the powder coating booth using a suspended conveyor. The decorative surface of the aluminum material, i.e. the surface to be coated, is aligned with the electrostatic spray gun and suspended, while maintaining a distance of 100mm between the aluminum material and the spray gun.

[0038] S4 electrostatic spraying: A high-voltage negative electrode is connected to the metal spray cup and electrode needle at the head of the electrostatic spray gun, and the workpiece to be sprayed is grounded to form a positive electrode, so that a strong electrostatic field is formed between the spray gun and the workpiece. Compressed air transports powder from the powder supply tank to the spray cup and electrode needle of the spray gun through the powder pipe. During this process, the powder carries a negative charge and enters the electrostatic field.

[0039] The raw material powder includes the following components: 65 parts of thermosetting epoxy resin; 25 parts of polyurethane resin; 50 parts of curing agent, specifically triglycidyl isocyanurate; 3 parts of dispersant, specifically sodium tripolyphosphate; 10 parts of pigment; 10 parts of graphene oxide; and 8 parts of precipitated barium sulfate.

[0040] Set the process parameters for the electrostatic spray gun, setting the spraying pressure to 0.15MPa, voltage to 110kV, and current to 50μA. Use the electrostatic spray gun to perform powder coating on the aluminum surface, controlling the coating thickness to 65-90μm to obtain a powder coating.

[0041] S5 Curing: The sprayed aluminum material is sent into the curing oven and heated to 160℃ for 15 minutes.

[0042] S6 Material Inspection: Remove the cured aluminum material, cool it to room temperature, and inspect the powder coating.

[0043] Example 2 An electrostatic powder coating process includes the following steps: S1 Aluminum Material Pretreatment: Prepare the aluminum material to be sprayed, and grind and trim the aluminum material using 240# sandpaper to make the surface of the aluminum material to be sprayed smooth.

[0044] S2 Aluminum Surface Treatment: This involves using chemical methods to treat the surface of aluminum, specifically including the following steps: S2a: The polished aluminum material is then sandblasted twice. The first sandblasting uses 0.5mm abrasive particles for 30 seconds, and the second sandblasting uses 1mm abrasive particles for 10 seconds. The angle between the sandblasting directions of the two sandblasting processes is set to 100°. Sandblasting removes dirt and impurities from the aluminum surface, eliminates surface unevenness, and creates a certain degree of roughness.

[0045] S2b: Prepare a degreasing solution, which includes 18 g / L of H3PO4 and 8 g / L of OP-10 emulsifier. The aluminum surface is degreased by the degreasing solution, and the oxide film on the aluminum surface can be removed by reacting with the degreasing solution.

[0046] S2c: Rinse the degreased aluminum material with clean water for 2 minutes, and then perform surface conditioning on the aluminum material. Colloidal titanium is used for surface conditioning, which changes the properties of the aluminum material surface and makes it more active.

[0047] S2d: Prepare a zinc-based phosphating solution and use it to phosphate aluminum materials, so that a phosphating film is formed on the surface of the aluminum materials. The phosphating film enhances the corrosion resistance of the aluminum materials and also enhances the adhesion of the aluminum materials surface.

[0048] The phosphating solution is formulated with 25 g / L H3PO4, 6 g / L NaF, 0.9 g / L (NH4)2MoO4, 3 g / L FeO, and 18 g / L ZnNO3.

[0049] The phosphating solution is prepared using the following steps: Add 85% H3PO4 to a beaker, dilute with distilled water, weigh out ZnNO3 and FeO accordingly, stir with a magnetic stirrer until completely dissolved, then add NaF and (NH4)2MoO4 accelerator, stir until the solution is clear, measure the pH and adjust with NaOH solution to pH=3.

[0050] The prepared phosphating solution has a free acidity of 2.5 and a total acidity of 30. The aluminum material is treated at 50°C for 10 minutes, and the resulting phosphating film is dense and completely covers the surface of the aluminum material.

[0051] S2e: Perform a second cleaning on the phosphated aluminum material, using deionized water for 3 minutes.

[0052] S2f: Pre-dry the cleaned aluminum material by placing it in a drying oven, setting the drying temperature to 140℃, and removing it after 2 minutes of drying.

[0053] S3 Suspended Aluminum Material: The surface-treated aluminum material is transported to the powder coating booth using a suspended conveyor. The decorative surface of the aluminum material, i.e. the surface to be coated, is aligned with the electrostatic spray gun and suspended, while maintaining a distance of 120mm between the aluminum material and the spray gun.

[0054] S4 electrostatic spraying: A high-voltage negative electrode is connected to the metal spray cup and electrode needle at the head of the electrostatic spray gun, and the workpiece to be sprayed is grounded to form a positive electrode, so that a strong electrostatic field is formed between the spray gun and the workpiece. Compressed air transports powder from the powder supply tank to the spray cup and electrode needle of the spray gun through the powder pipe. During this process, the powder carries a negative charge and enters the electrostatic field.

[0055] The raw material powder includes the following components: 80 parts of thermosetting epoxy resin; 35 parts of polyurethane resin; 70 parts of curing agent, specifically triglycidyl isocyanurate; 6 parts of dispersant, specifically sodium tripolyphosphate; 25 parts of pigment; 15 parts of graphene oxide; and 12 parts of precipitated barium sulfate.

[0056] Set the process parameters for the electrostatic spray gun, setting the spraying pressure to 0.25MPa, voltage to 135kV, and current to 70μA. Use the electrostatic spray gun to perform powder coating on the aluminum surface, controlling the coating thickness to 65-90μm to obtain a powder coating.

[0057] S5 Curing: The sprayed aluminum material is sent into the curing oven and heated to 200℃ for 25 minutes.

[0058] S6 Material Inspection: Remove the cured aluminum material, cool it to room temperature, and inspect the powder coating.

[0059] Example 3 An electrostatic powder coating process includes the following steps: S1 Aluminum Material Pretreatment: Prepare the aluminum material to be sprayed, and grind and trim the aluminum material using 240# sandpaper to make the surface of the aluminum material to be sprayed smooth.

[0060] S2 Aluminum Surface Treatment: This involves using chemical methods to treat the surface of aluminum, specifically including the following steps: S2a: The polished aluminum material is then sandblasted twice. The first sandblasting uses 0.5mm abrasive particles for 30 seconds, and the second sandblasting uses 1mm abrasive particles for 10 seconds. The angle between the sandblasting directions of the two sandblasting processes is set to 90°. Sandblasting removes dirt and impurities from the aluminum surface, eliminates surface unevenness, and creates a certain degree of roughness.

[0061] S2b: Prepare a degreasing solution, which includes 16 g / L of H3PO4 and 6 g / L of OP-10 emulsifier. The aluminum surface is degreased by the degreasing solution, and the oxide film on the aluminum surface can be removed by reacting with the degreasing solution.

[0062] S2c: Rinse the degreased aluminum material with clean water for 2 minutes, and then perform surface conditioning on the aluminum material. Colloidal titanium is used for surface conditioning, which changes the properties of the aluminum material surface and makes it more active.

[0063] S2d: Prepare a zinc-based phosphating solution and use it to phosphate aluminum materials, so that a phosphating film is formed on the surface of the aluminum materials. The phosphating film enhances the corrosion resistance of the aluminum materials and also enhances the adhesion of the aluminum materials surface.

[0064] The formulation of the phosphating solution is 23 g / L H3PO4, 5 g / L NaF, 0.8 g / L (NH4)2MoO4, 2 g / L FeO, and 16 g / L ZnNO3.

[0065] The phosphating solution is prepared using the following steps: Add 85% H3PO4 to a beaker, dilute with distilled water, weigh out ZnNO3 and FeO accordingly, stir with a magnetic stirrer until completely dissolved, then add NaF and (NH4)2MoO4 accelerator, stir until the solution is clear, measure the pH and adjust it with NaOH solution to pH=4.

[0066] The prepared phosphating solution has a free acidity of 2 and a total acidity of 27. The aluminum material is treated at 45°C for 8 minutes, and the resulting phosphating film is dense and completely covers the surface of the aluminum material.

[0067] S2e: Perform a second cleaning on the phosphated aluminum material, using deionized water for 3 minutes.

[0068] S2f: Pre-dry the cleaned aluminum material by placing it in a drying oven, setting the drying temperature to 130℃, and removing it after 3 minutes of drying.

[0069] S3 Suspended Aluminum Material: The surface-treated aluminum material is transported to the powder coating booth using a suspended conveyor. The decorative surface of the aluminum material, i.e. the surface to be coated, is aligned with the electrostatic spray gun and suspended, while maintaining a distance of 110mm between the aluminum material and the spray gun.

[0070] S4 electrostatic spraying: A high-voltage negative electrode is connected to the metal spray cup and electrode needle at the head of the electrostatic spray gun, and the workpiece to be sprayed is grounded to form a positive electrode, so that a strong electrostatic field is formed between the spray gun and the workpiece. Compressed air transports powder from the powder supply tank to the spray cup and electrode needle of the spray gun through the powder pipe. During this process, the powder carries a negative charge and enters the electrostatic field.

[0071] The raw material powder includes the following components: 70 parts thermosetting epoxy resin; 30 parts polyurethane resin; 60 parts curing agent, specifically triglycidyl isocyanurate; 5 parts dispersant, specifically sodium tripolyphosphate; 20 parts pigment; 20 parts graphene oxide; and 10 parts precipitated barium sulfate.

[0072] Set the process parameters for the electrostatic spray gun, setting the spraying pressure to 0.2MPa, voltage to 125kV, and current to 60μA. Use the electrostatic spray gun to perform powder spraying on the aluminum surface, controlling the coating thickness to 65-90μm to obtain a powder coating.

[0073] S5 Curing: The sprayed aluminum material is sent into the curing oven and heated to 180℃ for 20 minutes.

[0074] S6 Material Inspection: Remove the cured aluminum material, cool it to room temperature, and inspect the powder coating.

[0075] Performance testing 1. Adhesion test The adhesion of the aluminum powder coatings of Examples 1 to 3 was tested according to GB / T 9286 *Paints and Varnishes - Cross Cut Test*, and the results were recorded in Table 1.

[0076] 1. Film thickness According to GB / T 4957 *Non-magnetic base metal - Measurement of thickness of non-conductive coatings - Eddy current method*, the film thickness of the aluminum powder coatings of Examples 1 to 3 was measured by an eddy current thickness gauge, and the measurement results were recorded in Table 1.

[0077] 2. Color difference The color difference of the aluminum powder coatings of Examples 1 to 3 was tested according to GB / T 11186.3 *Methods for measuring the color of coatings - Part 3: Calculation of color difference*, and the results were recorded in Table 1.

[0078] 3. Salt spray corrosion resistance The aluminum powder coatings of Examples 1 to 3 were subjected to an acetic acid salt spray test according to GB / T 10125 *Corrosion tests in artificial atmospheres - Salt spray tests*.

[0079] After 1000 hours of the acetic acid salt spray test, the surface of the tested coating is visually inspected. If no blisters or peeling occur, and the unilateral penetration corrosion under the film on both sides of the scribe line does not exceed 4 mm, the test result is qualified; otherwise, it is unqualified. The results are recorded in Table 1.

[0080] 4. Wear resistance The wear resistance of the aluminum powder coatings of Examples 1 to 3 was tested by the falling sand test method according to GB / T 12967.7 *Test methods for anodic oxide films of aluminium and its aluminium alloys - Part 7: Determination of wear resistance of anodic oxide films using falling sand tester*, and the results were recorded in Table 1.

[0081] Wear resistance coefficient = mass of abrasive / local film thickness Table 1 Adhesion rating Level 0 Level 0 Level 0 Film thickness (μm) 68 75 82 Color difference 0.3 0.2 0.2 Salt spray corrosion resistance qualified qualified qualified Wear coefficient (g / μm) 563 578 574 It can be seen that the adhesion grades of the aluminum materials of Example 1, Example 2 and Example 3 obtained by the electrostatic powder spraying process of the present application are all 0, indicating that the powder coating has excellent adhesion on the surface of the aluminum material, and the prepared aluminum material has advantageous wear resistance and good corrosion resistance, which meet the standard requirements.

[0082] This specific embodiment is only an explanation of the present application, and it is not a limitation to the present application. Those skilled in the art can make modifications without inventive contribution to this specific embodiment as needed after reading this specification, but they are protected by patent law as long as they are within the scope of the claims of the present application.

Claims

1. An electrostatic powder spraying process, characterized in that, Includes the following steps: S1 Aluminum Material Pretreatment: Grinding and finishing the aluminum material to make the surface smooth; S2 Aluminum Surface Treatment: This involves using chemical methods to treat the aluminum surface, removing the oxide film and simultaneously forming a phosphate film. Step S2 specifically includes the following steps: S2a: The pre-treated aluminum surface is subjected to two liquid sandblasting treatments, with abrasive particle sizes of 0.5mm and 1mm respectively. The first sandblasting treatment lasts for 30 seconds, and the second sandblasting treatment lasts for 10 seconds. The included angle between the sandblasting directions of the two sandblasting treatments is 70-100°. S2b: Use degreasing solution to degrease the surface of the sandblasted aluminum material; S2c: Rinse the degreased aluminum material with clean water, and use colloidal titanium to adjust the surface of the aluminum material; S2d: Phosphating treatment is performed on the rinsed aluminum material using a phosphating solution to form a phosphating film on the aluminum surface. The phosphating solution is composed of the following raw materials: H3PO4 21-25g / L, NaF 4-6g / L, (NH4)2MoO4 0.6-0.9g / L, FeO 1-3g / L, ZnNO3 14-18g / L; S2e: Phosphated aluminum materials are cleaned a second time with deionized water; S2f: Pre-dry the cleaned aluminum material at a temperature of 120-140℃. S3 Suspended Aluminum Material: Transfer the surface-treated aluminum material into the powder coating booth, align the decorative surface with the electrostatic spray gun and suspend it, keeping the distance between the aluminum material and the electrostatic spray gun at 100-120mm. S4 electrostatic spraying: Using an electrostatic spray gun, raw material powder is sprayed onto the surface of aluminum to form a powder coating. The raw material powder includes: thermosetting epoxy resin, polyurethane resin, curing agent, dispersant, pigment, graphene oxide and precipitated barium sulfate. The spraying process parameters are: the spraying pressure of the electrostatic spray gun is set to 0.15-0.25MPa, the voltage is 110-135kV, and the current is 50-70μA. S5 Curing: The sprayed aluminum material is sent into the curing oven, the heating temperature is set to 160-200℃, and the curing time is 15-25min; S6 Material Inspection: After the cured aluminum material is removed and cooled to room temperature, the powder coating is inspected.

2. An electrostatic powder spraying process according to claim 1, characterized in that, The raw material powder includes: 65-80 parts of thermosetting epoxy resin; 25-35 parts of polyurethane resin; 50-70 parts of curing agent; 3-6 parts dispersant; 10-25 parts pigment; 10-15 parts of graphene oxide; 8-12 parts of barium sulfate by precipitation method.

3. An electrostatic powder spraying process according to claim 1, characterized in that: In step S2d, the process parameters for phosphating are: free acidity 1.5-2.5; total acidity 24-30; phosphating temperature 40-50℃; phosphating time 5-10min.

4. An electrostatic powder spraying process according to claim 1, characterized in that: In step S2b, the selected oiling fluid includes the following components: H3PO4 15-18 g / L, OP-10 emulsifier 4-8 g / L.

5. An electrostatic powder spraying process according to claim 2, characterized in that: The curing agent is triglycidyl isocyanurate.

6. An electrostatic powder spraying process according to claim 2, characterized in that: The dispersant used is sodium tripolyphosphate.

7. The electrostatic powder coating process according to claim 1, characterized in that: In step S4, the thickness of the powder coating is controlled to be 65-90 μm.