Electrostatic powder spraying and curing process for anti-corrosion layer on surface of cabinet body

Abstract

The invention relates to an electrostatic powder spraying and curing process for an anticorrosive coating on the surface of a cabinet body, and belongs to the technical field of cabinet body surface processing, the electrostatic powder spraying and curing process comprises the following steps: S1, carrying out surface pretreatment on a metal cabinet body through a pretreatment and nano conversion film generation unit, and then carrying out phosphating treatment by adopting a nano composite phosphating solution; s2, bottom layer spraying and curing, wherein an epoxy powder bottom layer spraying and curing unit is adopted to evenly spray epoxy powder coating on the surface of the cabinet body treated in the S1; s3, after the epoxy powder anti-corrosion bottom layer is completely cooled, polyester powder coating is evenly sprayed to the surface of the bottom layer through a polyester powder surface layer spraying and stepped curing unit, then the cabinet body is fed into a curing oven, and S4, cooling and inspection are conducted. According to the invention, the formed composite coating structure of the nano composite conversion film, the epoxy anticorrosive bottom layer and the polyester weather-resistant surface layer gives full play to the advantages of each layer of material, and synergistically realizes extremely high adhesive force, salt spray corrosion resistance, ultraviolet aging resistance, impact resistance and decoration.

Description

Technical Field

[0001] This invention relates to the field of cabinet surface processing technology, and in particular to an electrostatic powder coating and curing process for an anti-corrosion layer on the cabinet surface. Background Technology

[0002] Electrostatic powder coating has become the mainstream process for anti-corrosion treatment of metal cabinet surfaces due to its environmental protection, high efficiency and excellent coating performance. However, for outdoor cabinets used in high temperature and humidity, high salt spray or strong ultraviolet radiation environments such as coastal areas and industrial areas, traditional coating systems and processes still have obvious limitations and cannot meet the requirements for long-term anti-corrosion use.

[0003] In terms of coating systems, existing technologies mostly adopt coatings with a single performance orientation. For example, the existing publication CN202411576843.6 describes a heavy-duty anti-corrosion and anti-scaling epoxy powder coating, its preparation method and application. This has developed a heavy-duty anti-corrosion epoxy powder coating with extremely high adhesion and corrosion resistance. However, its UV resistance and outdoor weather resistance are poor, and it is prone to chalking and loss of gloss after long-term outdoor use. Other technologies focus on adding specific functions such as antistatic and antibacterial properties to polyester coatings. However, these single coatings are often difficult to match the overall anti-corrosion performance of epoxy systems.

[0004] In terms of materials technology, introducing nanomaterials into coatings is a common method to improve performance. However, traditional methods usually involve directly adding nanoparticles to the coating, which results in uneven dispersion and easy agglomeration, affecting the performance improvement effect. Although there are existing publications such as CN120758071A on modified epoxy powder coating nano-reinforcing agents and their preparation methods, which are dedicated to solving the agglomeration problem of nano-reinforcing agents in epoxy coatings through core-shell structures, their technology is still focused on the modification of single coating materials.

[0005] In terms of curing process, for thicker coatings or composite coatings, the traditional constant temperature one-time curing process is prone to stress concentration due to internal and external temperature differences, which affects the mechanical properties of the coating. Existing technologies have adopted multi-stage curing solutions, but these are mostly for non-metallic substrates such as MDF, and their segmentation mainly relies on specific curing equipment such as infrared and ultraviolet light, rather than being optimized based on the chemical reaction characteristics of composite powder coatings on metal substrates.

[0006] In summary, existing technologies lack a coating solution that can systematically and comprehensively address the long-term protection of metal cabinets in extreme outdoor environments, from materials to underlying processes. To address this, we propose an electrostatic powder coating and curing process for the anti-corrosion layer on the cabinet surface. Through a double-layer powder coating design with an anti-corrosion base layer and a weather-resistant top layer, combined with optimized nanocomposite pretreatment and stepped curing processes, the coating's adhesion, salt spray corrosion resistance, weather resistance, and impact resistance are significantly improved. This process is particularly suitable for the long-term protection of metal cabinets such as server racks and distribution boxes in harsh outdoor environments. Summary of the Invention

[0007] This invention provides an electrostatic powder coating and curing process for an anti-corrosion layer on a cabinet surface. It solves the problem that a single coating system cannot simultaneously achieve long-term corrosion protection and excellent weather resistance, thus balancing the high corrosion resistance of the base layer with the strong weather resistance of the top layer. It also addresses the issue of uneven dispersion and agglomeration when nanomaterials are directly added to the coating. By introducing nanomaterials into the phosphating solution during the pretreatment stage, a nanocomposite conversion film is formed as an intermediate layer, fundamentally preventing the agglomeration of nanoparticles in the coating and enhancing the adhesion between the coating and the substrate. Furthermore, it solves the problem of internal stress and reduced mechanical properties caused by one-time high-temperature curing of thick or composite coatings. Through a two-stage process of low-temperature melting and leveling followed by high-temperature full cross-linking, curing stress is effectively reduced, improving the coating's density and impact resistance.

[0008] The present invention provides the following solution to the above-mentioned technical problems: an electrostatic powder coating and curing process for an anti-corrosion layer on the surface of a cabinet, comprising a pretreatment and nano-conversion film generation unit, an epoxy powder underlayer coating and curing unit, a polyester powder toplayer coating and stepped curing unit, and a suspended conveying system and a central control system connecting the above units, characterized by comprising the following steps: S1. Pre-processing; The metal cabinet is pretreated by a pretreatment and nano-conversion film generation unit, including degreasing, rust removal and water washing. Then, it is phosphated with nano-composite phosphating solution to form a nano-composite conversion film. Finally, it is washed with water and dried. S2. Base coat spraying and curing; The epoxy powder undercoat spraying and curing unit is used to uniformly spray epoxy powder coating onto the surface of the cabinet after S1 treatment. Then the cabinet is sent into the curing oven and kept at 180-190℃ for 15-20 minutes to allow the epoxy powder to melt, flow and completely cure, forming an epoxy powder anti-corrosion undercoat. S3. Topcoat spraying and curing; After the epoxy powder anti-corrosion base layer has completely cooled, the polyester powder coating is evenly sprayed onto the base layer surface using a polyester powder topcoat spraying and stepped curing unit. Then, the cabinet is sent into the curing oven and cured using a stepped heating program: first, the temperature is raised to 150-160℃ at a rate of 5-10℃ / min and held for 5-8 minutes; then, the temperature is raised to 190-200℃ and held for 10-15 minutes to completely cure the polyester powder and form a polyester powder weather-resistant topcoat. S4. Cooling and Inspection: Allow the cabinet to cool naturally or by force to room temperature, and inspect the appearance, thickness and performance of the composite coating.

[0009] Based on the above technical solution, the present invention can be further improved as follows.

[0010] Furthermore, the composite coating comprises a nanocomposite conversion film, an epoxy powder anti-corrosion underlayer, and a polyester powder weather-resistant top layer, formed sequentially from the inside out on the surface of the metal cabinet substrate. The epoxy powder anti-corrosion underlayer has a thickness of 50-80 μm, and the polyester powder weather-resistant top layer has a thickness of 30-50 μm. The 50-80 μm epoxy underlayer provides sufficient anti-corrosion barrier and mechanical strength, while the 30-50 μm polyester top layer ensures excellent weather resistance and decorative properties while avoiding excessive thickness that could lead to increased costs or cracking risks.

[0011] Furthermore, in step S1, the nanocomposite phosphating solution contains phosphate, accelerator, and nano-silica or nano-zirconia particles. The phosphating temperature is 38±2℃, and the treatment time is 5-7 minutes. Adding nano-silica or zirconia particles can enhance the density, hardness, and adhesion to subsequent coatings of the conversion film. Precisely controlling the treatment temperature at 38±2℃ and the time at 5-7 minutes can ensure that the nanoparticles effectively and uniformly participate in the film-forming reaction, forming a stable and consistent nanocomposite conversion film, providing an excellent adhesion substrate for subsequent coatings.

[0012] Furthermore, during the electrostatic spraying process in steps S2 and S3, the spraying voltage is 60-80kV, the spray gun air pressure is 0.4-0.6MPa, and the distance between the spray gun and the cabinet surface is 150-250mm. Powder spraying is carried out in an automatic spraying booth equipped with a powder recovery system. The recovered powder is sieved and then mixed with new powder in a certain proportion for reuse. The voltage of 60-80kV and the air pressure of 0.4-0.6MPa ensure that the powder is fully charged and effectively atomized, while the distance of 150-250mm optimizes the powder application rate and coating uniformity. The operation in an automatic spraying booth equipped with a recovery system, combined with the powder recovery and reuse process, not only ensures the cleanliness and safety of the production environment, but also significantly improves the utilization rate of powder materials and reduces production costs.

[0013] Furthermore, in the stepped heating process described in step S3, during the first stage of heat preservation at 150-160℃, the polyester powder initially melts and levels; during the second stage of heat preservation at 190-200℃, the polyester powder undergoes full cross-linking and curing. The heat preservation in the first stage (150-160℃) aims to allow the polyester powder to fully melt and level, forming a smooth, defect-free coating surface, and reducing the retention of volatile substances or poor leveling caused by rapid heating. The heat preservation in the second stage (190-200℃) provides sufficient energy and time to promote the full cross-linking reaction of the polyester resin, achieving complete curing, thereby obtaining the best mechanical properties, chemical resistance, and durability. The two-stage separation design effectively alleviates the internal stress that may be generated by single high-temperature curing.

[0014] Furthermore, the pretreatment and nano-conversion membrane generation unit sequentially includes a spray-type pretreatment tunnel, a nano-composite phosphating tank, a deionized water immersion tank, and a bridge-type drying oven. The spray-type pretreatment tunnel is sequentially equipped with an alkaline degreasing spray section and a clean water rinsing spray section. The nano-composite phosphating tank is used to hold phosphating solution containing nanoparticles, and the tank is equipped with an immersion heating pipe and a pipeline air stirring system. The epoxy powder undercoat spraying and curing unit includes a first automatic electrostatic powder spraying chamber, a first powder supply center and a first hot air circulation curing oven. The first automatic electrostatic powder spraying chamber is equipped with a programmable automatic electrostatic spray gun and a powder recovery system. The first powder supply center is connected to the automatic electrostatic spray gun. The polyester powder coating and stepped curing unit includes a second automatic electrostatic powder coating chamber, a second powder supply center, and an intelligent temperature-controlled curing oven. The second automatic electrostatic powder coating chamber is equipped with a programmable automatic electrostatic spray gun and a powder recovery system. The second powder supply center is connected to the automatic electrostatic spray gun. The suspended conveyor system is an aerial friction conveyor line. The central control system is built on a programmable logic controller and is used to coordinate and control the start-up, stop and process parameters of each unit, ensuring the consistency of process parameters and reliable linkage of the production process.

[0015] Furthermore, the temperature control system of the nanocomposite phosphating tank adopts a PID temperature controller to maintain the tank temperature at 38±2℃; the bridge-type drying oven is a multi-temperature zone hot air circulation drying oven. The PID temperature controller can achieve precise and stable temperature control (±2℃) of the nanocomposite phosphating tank, which is crucial for the stable dispersion of nanoparticles and the uniformity of the conversion film quality. The multi-temperature zone hot air circulation bridge-type drying oven can provide a uniform and efficient drying effect, ensuring that the workpiece is completely dry before entering the spraying process, and avoiding the negative impact of moisture on the coating quality.

[0016] Furthermore, the powder recovery system is a two-stage recovery system, including a cyclone separator and a cartridge filter; the curing temperature of the first hot air circulating curing oven is 180-190℃, and it is equipped with a hot air circulating fan. The two-stage recovery system (cyclone separation + cartridge filtration) achieves efficient and graded recovery of oversprayed powder, improves the quality and reuse rate of the recovered powder, and clarifies the temperature range (180-190℃) of the first curing oven and its hot air circulating fan configuration, ensuring that the epoxy underlayer can be fully cured in a uniform and stable temperature field to obtain the expected anti-corrosion and physical properties.

[0017] Furthermore, the intelligent temperature-controlled curing oven adopts a multi-segment independent temperature control design, and its control system adopts an executable step heating program, which includes: first, holding the workpiece at 150-160℃ for 5-8 minutes, and then continuing to heat it to 190-200℃ and holding it for 10-15 minutes.

[0018] The beneficial effects of this invention are as follows: This invention provides an electrostatic powder coating and curing process for an anti-corrosion layer on the surface of a cabinet, which has the following advantages: 1. Excellent comprehensive protection performance: The composite coating structure of "nanocomposite conversion film + epoxy anti-corrosion base layer + polyester weather-resistant top layer" fully leverages the advantages of each layer material, and synergistically achieves extremely high adhesion, salt spray corrosion resistance, UV aging resistance, impact resistance and decorative properties. It is especially suitable for the long-term protection requirements of metal cabinets in extreme outdoor environments such as coastal areas and industrial areas. 2. The process is advanced and controllable. The nano-composite phosphating process improves the bonding strength and corrosion resistance of the substrate and coating. The use of automatic electrostatic spraying and a two-stage powder recycling system improves the powder application rate, material utilization rate and environmental friendliness. The stepped temperature curing program for polyester coatings is optimized based on material characteristics, which improves the curing quality and coating performance. 3. The entire process is connected in series by a suspended conveyor system and coordinated and controlled by a programmable logic controller-based central control system. Each unit equipment has the ability to control precise process parameters, ensuring process stability and product consistency, and is suitable for large-scale production.

[0019] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail below with reference to the accompanying drawings. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 A process flow diagram of an electrostatic powder coating and curing process for an anti-corrosion layer on the surface of a cabinet, provided in an embodiment of the present invention; Figure 2 This is a system architecture diagram of an electrostatic powder coating and curing process for an anti-corrosion layer on the surface of a cabinet, provided in an embodiment of the present invention. Detailed Implementation

[0021] The following is in conjunction with the appendix Figure 1-2 The principles and features of the present invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. The invention is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0022] It should be noted that when a component is described as "fixed to" another component, it can be directly on the other component or may have a component in between. When a component is considered "connected to" another component, it can be directly connected to the other component or may have a component in between. When a component is considered "set on" another component, it can be directly set on the other component or may have a component in between. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] like Figure 1 As shown, the present invention provides an electrostatic powder coating and curing process for an anti-corrosion layer on the surface of a cabinet, including a pretreatment and nano-conversion film generation unit, an epoxy powder underlayer coating and curing unit, a polyester powder toplayer coating and stepped curing unit, and a suspension conveying system and a central control system that connect the above units. The pretreatment and nano-conversion membrane generation unit includes a spray-type pretreatment tunnel, a nano-composite phosphating tank, a deionized water immersion tank, and a bridge-type drying oven. The nano-composite phosphating tank is equipped with an immersion heating tube and a pipeline air stirring system. Its temperature control system adopts a PID temperature controller. The bridge-type drying oven has a three-temperature zone hot air circulation structure. The epoxy powder undercoat spraying and curing unit includes a first automatic electrostatic powder spraying booth, a first powder supply center and a first hot air circulation curing oven. The spraying booth is equipped with a programmable control automatic electrostatic spray gun group and connected to a two-stage powder recovery system consisting of a cyclone separator and a cartridge filter. The polyester powder coating and stepped curing unit includes a second automatic electrostatic powder coating chamber, a second powder supply center, and an intelligent temperature-controlled curing oven. The intelligent temperature-controlled curing oven adopts a three-zone independent temperature control design, and the control system is preset with a stepped temperature rise curing program. The overhead conveyor system uses an aerial friction conveyor line. The central control system is built on a programmable logic controller (PLC) and communicates with the distributed I / O stations and human-machine interfaces (HMIs) of each unit via industrial Ethernet to realize the start-up and shutdown of the entire production line, the setting of process parameters, and the monitoring of process data.

[0025] like Figure 2 As shown, the specific working principle and usage method of this invention are as follows: The first step is the pretreatment of the cabinet surface and the generation of a nanocomposite conversion film. The purpose of this step is to obtain a clean and active metal surface and to build an underlayer that enhances the adhesion of the coating. Degreasing and cleaning: The metal cabinet is sent into the spray pretreatment tunnel via a suspended chain. First, it is sprayed with alkaline degreasing solution (such as Henkel P3-topclean163) at a temperature of 50-60℃ for no less than 3 minutes to thoroughly remove oil stains. Then, it is rinsed with room temperature water in two stages of countercurrent spraying. Surface conditioning and phosphating: After degreasing and washing, the workpiece enters the nanocomposite phosphating process. The cabinet is completely immersed in the nanocomposite phosphating solution (e.g., zinc-based phosphating solution containing 1-3% nano silica dispersion). The temperature of the solution should be automatically controlled at 38±2℃ by an immersion titanium heating tube (such as the JUMOTYA-201 temperature control system). The processing time is 5-7 minutes. During this time, the pipe-type air stirring system (such as the JASUN oil-free silent air compressor) installed at the bottom of the tank continuously and slowly stirs the solution to ensure that the nanoparticles are evenly dispersed and participate in film formation. Post-treatment and washing and drying: After phosphating, the cabinet is rinsed in two deionized water tanks and then enters a bridge-type drying oven (hot air circulation drying oven). The oven is set with three temperature zones and adopts stepped heating (80℃→120℃→100℃). The total drying time is about 12-15 minutes to ensure that the gaps and interior of the workpiece are completely dry and there is no moisture residue. The second step involves spraying and curing an epoxy powder anti-corrosion undercoat to form a coating that combines excellent adhesion with barrier anti-corrosion properties. Electrostatic spraying: The cabinet, completely cooled to room temperature, is sent into an automatic electrostatic powder coating chamber (such as the German Wagner AutoJet series). The chamber is equipped with multiple programmable automatic spray guns (such as GEMA OptiFlex Atom). The spray gun trajectory is preset by a PLC (such as Siemens S7-1200) based on the 3D model of the cabinet. The key spraying parameters are set as follows: electrostatic high voltage 65-75kV, atomizing air pressure 0.5-0.6MPa, powder supply air pressure 0.05-0.10MPa, and the distance between the spray gun and the workpiece is maintained at 200-250mm. During the spraying process, the unadsorbed powder is sucked in by a high-power recovery fan (such as the Swiss GEMA's PowderBox recovery system), filtered by a cyclone separator and a fine filter, and returned to the powder supply center. It is then mixed with new powder at a ratio of 1:3 and recycled, with a utilization rate of over 98%. After high-temperature curing and inspection to ensure no defects, the coated cabinet is immediately sent to a gas-fired hot air circulating curing oven (such as NORDSONEco-Cure). The curing oven uses a PID (proportional-integral-derivative) temperature control algorithm, whose core control logic can be simplified to: output power = Kp × temperature deviation + Ki × integral (temperature deviation) + Kd × derivative (temperature deviation) to achieve precise and stable oven temperature. The oven temperature is set at 185±2℃, and the workpiece is kept in the oven for 18 minutes. The strong convection fan in the oven ensures uniform heat transfer, allowing the epoxy powder to fully melt, level, and undergo cross-linking reaction to form a continuous and dense coating with a thickness controlled at 60±5μm. The third step involves spraying and step-by-step curing of a polyester powder weather-resistant surface layer to create a weather-resistant decorative layer on top of the base layer. Secondary electrostatic spraying: After the epoxy base layer has completely cooled, the cabinet enters a second independent clean spraying room (equipment model is the same as in step two). The same but independent powder supply and spraying system as the base layer is used to spray ultra-weather resistant polyester powder (such as AkzoNobel Interpon D2000 series). In order to ensure the gloss and leveling of the surface layer, the spraying voltage can be slightly increased to 70-80kV. The other parameters are similar to the base layer spraying. The final surface layer thickness is controlled at 40±5μm. Stepped heating program: This step employs a unique two-step heating and curing algorithm, executed by the curing oven's PLC. The specific program is as follows: The first stage (melting and leveling stage): After the cabinet enters the curing oven, the control system raises the surface temperature of the workpiece from room temperature to 155±3℃ at a relatively fast heating rate (about 8-10℃ / min) and holds it at this temperature for 7 minutes. The core of the algorithm in this stage is to maintain a constant temperature, so that the polyester powder has enough time to fully melt, wet the bottom surface and complete the leveling, and expel the internal gas. The second stage (complete cross-linking stage): After the heat preservation is completed, the control system instructs the heating system to increase the power and continue to heat up at a rate of 5-8℃ / min until the surface temperature of the workpiece reaches 198±2℃. Then, it is kept at this temperature for 13 minutes. The core of the algorithm in this stage is to ensure the duration of high temperature, so as to promote the functional groups of polyester resin to undergo a full chemical cross-linking reaction, and achieve the final hardness, chemical resistance and weather resistance. The fourth step is cooling and final inspection; Once cured, the cabinet is transferred to a cooling zone, where it is cooled to below 60°C within 10 minutes using clean, forced-air cooling (such as a high-power axial fan array), then allowed to cool naturally to room temperature before undergoing a full inspection. Visual inspection: Under a standard light source box, the coating should be flat, smooth, free of color difference, particles, pinholes and other defects. Thickness inspection: Use a magnetic or eddy current thickness gauge to measure at least 10 points on each side of the cabinet. The total thickness should reach 100-110μm and conform to the design ratio of the bottom and top layer thickness. Performance sampling inspection: Samples are taken periodically and subjected to cross-cut adhesion test, impact resistance test, etc., according to national standards. After completion, samples are sent for neutral salt spray test and ultraviolet accelerated aging test.

[0026] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Content not described in detail in this specification is prior art known to those skilled in the art.

[0027] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. An electrostatic powder coating and curing process for an anti-corrosion layer on a cabinet surface, comprising a pretreatment and nano-conversion film generation unit, an epoxy powder undercoat coating and curing unit, a polyester powder topcoat coating and stepped curing unit, and a suspended conveying system and a central control system connecting the above units, characterized in that, Includes the following steps: S1. Pre-processing; The metal cabinet is pretreated by a pretreatment and nano-conversion film generation unit, including degreasing, rust removal and water washing. Then, it is phosphated with nano-composite phosphating solution to form a nano-composite conversion film. Finally, it is washed with water and dried. S2. Base coat spraying and curing; The epoxy powder undercoat spraying and curing unit is used to uniformly spray epoxy powder coating onto the surface of the cabinet after S1 treatment. Then the cabinet is sent into the curing oven and kept at 180-190℃ for 15-20 minutes to allow the epoxy powder to melt, flow and completely cure, forming an epoxy powder anti-corrosion undercoat. S3. Topcoat spraying and curing; After the epoxy powder anti-corrosion base layer has completely cooled, the polyester powder coating is evenly sprayed onto the base layer surface using a polyester powder topcoat spraying and stepped curing unit. Then, the cabinet is sent into the curing oven and cured using a stepped heating program: first, the temperature is raised to 150-160℃ at a rate of 5-10℃ / min and held for 5-8 minutes; then, the temperature is raised to 190-200℃ and held for 10-15 minutes to completely cure the polyester powder and form a polyester powder weather-resistant topcoat. S4. Cooling and Inspection: Allow the cabinet to cool naturally or by force to room temperature, and inspect the appearance, thickness and performance of the composite coating.

2. The electrostatic powder coating and curing process for an anti-corrosion layer on the surface of a cabinet according to claim 1, characterized in that, The composite coating comprises a nanocomposite conversion film, an epoxy powder anti-corrosion underlayer, and a polyester powder weather-resistant top layer, which are formed sequentially from the inside to the outside on the surface of the metal cabinet substrate. The thickness of the epoxy powder anti-corrosion underlayer is 50-80μm, and the thickness of the polyester powder weather-resistant top layer is 30-50μm.

3. The electrostatic powder coating and curing process for an anti-corrosion layer on the surface of a cabinet according to claim 1, characterized in that, In step S1, the nanocomposite phosphating solution contains phosphate, accelerator and nano silica or nano zirconium oxide particles, and the phosphating temperature is 38±2℃ and the treatment time is 5-7 minutes.

4. The electrostatic powder coating and curing process for an anti-corrosion layer on the surface of a cabinet according to claim 1, characterized in that, During the electrostatic spraying process in steps S2 and S3, the spraying voltage is 60-80kV, the spray gun air pressure is 0.4-0.6MPa, and the distance between the spray gun and the cabinet surface is 150-250mm. The powder spraying is carried out in an automatic spraying booth equipped with a powder recovery system. The recovered powder is screened and then mixed with new powder in proportion for reuse.

5. The electrostatic powder coating and curing process for an anti-corrosion layer on the surface of a cabinet according to claim 1, characterized in that, In the stepped heating process described in step S3, during the first stage of heat preservation at 150-160℃, the polyester powder initially melts and levels; during the second stage of heat preservation at 190-200℃, the polyester powder undergoes full cross-linking and curing.

6. The electrostatic powder coating and curing process for an anti-corrosion layer on the surface of a cabinet according to claim 1, characterized in that, The pretreatment and nano-conversion membrane generation unit includes, in sequence, a spray-type pretreatment tunnel, a nano-composite phosphating tank, a deionized water immersion tank, and a bridge-type drying oven. The spray-type pretreatment tunnel is provided with an alkaline degreasing spray section and a clean water rinsing spray section. The nano-composite phosphating tank is used to hold phosphating solution containing nanoparticles. The tank is equipped with an immersion heating pipe and a pipeline air stirring system. The epoxy powder undercoat spraying and curing unit includes a first automatic electrostatic powder spraying chamber, a first powder supply center and a first hot air circulation curing oven. The first automatic electrostatic powder spraying chamber is equipped with a programmable automatic electrostatic spray gun and a powder recovery system. The first powder supply center is connected to the automatic electrostatic spray gun. The polyester powder coating and stepped curing unit includes a second automatic electrostatic powder coating chamber, a second powder supply center, and an intelligent temperature-controlled curing oven. The second automatic electrostatic powder coating chamber is equipped with a programmable automatic electrostatic spray gun and a powder recovery system. The second powder supply center is connected to the automatic electrostatic spray gun. The suspended conveyor system is an aerial friction conveyor line, and the central control system is built based on a programmable logic controller to coordinate and control the start-up, stop, and process parameters of each unit.

7. The electrostatic powder coating and curing process for an anti-corrosion layer on the surface of a cabinet according to claim 6, characterized in that, The temperature control system of the nanocomposite phosphating tank adopts a PID temperature controller to maintain the tank liquid temperature at 38±2℃; the bridge-type drying oven is a multi-temperature zone hot air circulation drying oven.

8. The electrostatic powder coating and curing process for an anti-corrosion layer on the surface of a cabinet according to claim 6, characterized in that, The powder recovery system is a two-stage recovery system, including a cyclone separator and a cartridge filter; the curing temperature of the first hot air circulating curing oven is 180-190℃, and it is equipped with a hot air circulating fan.

9. The electrostatic powder coating and curing process for an anti-corrosion layer on the surface of a cabinet according to claim 6, characterized in that, The intelligent temperature-controlled curing oven adopts a multi-segment independent temperature control design. Its control system adopts an executable step heating program, which includes: first, holding the workpiece at 150-160℃ for 5-8 minutes, and then continuing to heat it to 190-200℃ and holding it for 10-15 minutes.

Images