Method for improving orange peel of aluminum alloy hub through thermal electrostatic spraying

Abstract

The invention discloses a method for improving orange peel of an aluminum alloy hub through thermal electrostatic spraying, and belongs to the technical field of metal surface treatment. The invention aims to solve the problems of prominent orange peel defects, contradiction between coating hardness and adhesive force and the like during coating of bright black aluminum alloy hubs. The method comprises the following steps: raising the dehydration heating temperature to 150 DEG C and canceling forced cooling, so that a workpiece is subjected to thermal electrostatic spraying of high-leveling orange-peel-resistant black powder at 65-80 DEG C; then black paint and high-solid-content bright paint are sequentially sprayed, and the black paint and the high-solid-content bright paint are solidified together after being fused on the interface; and the surface layer bright paint is subjected to suspended cup type electrostatic spraying so as to realize super-thick uniform coating. Meanwhile, a universal protection plug with a conical head is adopted in the center cap groove, and reliable sealing is achieved through linear contact. According to the invention, the orange peel problem can be obviously improved, the coating has high hardness and excellent adhesive force, the process is simplified, the cost is reduced, and the method is particularly suitable for coating production of high-end bright black aluminum alloy hubs.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, and in particular to a method for improving orange peel texture in aluminum alloy wheel hubs using thermo-electrostatic spraying. Background Technology

[0002] Aluminum alloy wheels have become standard equipment in modern automobiles due to their lightweight, high strength, and excellent heat dissipation. Among them, glossy black wheels, with their deep and sophisticated visual appeal, have long dominated the market. The market's demands for wheel appearance quality are increasing, especially the smoothness of the surface. One of the core evaluation indicators is the "orange peel" grade after painting. Orange peel refers to tiny wavy defects on the coating surface, which seriously affect the product's appearance and optical mirror effect.

[0003] In the painting production of aluminum alloy wheels, a composite process of "powder primer + liquid topcoat" is commonly used. However, in actual production, the orange peel effect on glossy black products is significantly higher than on other low-gloss or gray-toned high-gloss products. This phenomenon has become a common problem in the industry, mainly due to the following reasons: First, from an optical perspective, glossy black has a "magnifying effect" on surface defects. Glossy black aims for extremely high specular reflectivity; any microscopic surface undulations cause the reflected image to be distorted and blurred, creating a strong visual contrast. In contrast, light-colored or matte surfaces can effectively conceal minor unevenness through light scattering.

[0004] Secondly, from a material properties perspective, glossy black coatings inherently present a contradiction between "leveling and curing." To achieve high blackness, a large amount of fine carbon black pigments needs to be added. These pigments significantly increase the viscosity of the coating system, hindering its flow (leveling). However, for production efficiency, the curing reaction must proceed rapidly. Once cross-linking begins, the viscosity rises sharply, and flow stops. Therefore, the time window for coating leveling is very short and demanding.

[0005] Third, from the perspective of process control, the existing process has the following problems: Energy waste and thermal stress: The "heating-forced cooling" mode is energy-intensive, and drastic temperature changes may affect coating adhesion.

[0006] Insufficient leveling power: When powder is sprayed on low-temperature workpieces, the melting start is slow and the effective leveling time is short.

[0007] Uniformity of film thickness is difficult to guarantee: The complex shape of the wheel hub leads to uneven electric field distribution, making it difficult to achieve consistent film thickness everywhere. Small differences in film thickness will be directly displayed as orange peel under glossy black.

[0008] The contradiction between interlayer bonding and hardness: To ensure interlayer adhesion, the bottom layer often needs to be incompletely cured, but this may sacrifice the overall hardness of the final coating; conversely, if the bottom layer is completely cured, the topcoat will be difficult to adhere.

[0009] Fourth, there is a lack of efficient and universal solutions in terms of tooling and auxiliary equipment. Wheel hub protection often uses dedicated protective plugs of "one type, one plug," which has poor versatility, high management costs, and poor sealing effect, which can easily lead to paint contamination of the assembly surface and affect subsequent vehicle assembly.

[0010] Currently, the industry lacks a systematic and effective solution to the orange peel effect on glossy black alloy wheels. Most companies still rely on traditional processes, barely controlling the appearance through post-processing sanding and rework, resulting in low production efficiency and failing to effectively improve the orange peel problem. Furthermore, the combination of a base layer of black powder with black paint and transparent powder is costly because the powder requires constant temperature for transportation and storage, making maintenance and storage difficult. The powder unit price is 2.5 to 3 times that of paint, leading to high costs. Therefore, there is an urgent need to develop a new coating process that can fundamentally improve the orange peel defect of glossy black aluminum alloy wheels. Summary of the Invention

[0011] This invention proposes a method for improving orange peel texture in aluminum alloy wheel hubs through thermo-electrostatic spraying, in order to solve the problems of prominent and difficult-to-control orange peel defects in glossy black coatings; the problems of high energy consumption, low efficiency and poor leveling of traditional "heating-strong cooling" spraying processes; the problem of difficulty in ensuring uniformity of electrostatic spraying film thickness on complex three-dimensional wheel hub workpieces; and the problem of difficulty in achieving both high-hardness coating and excellent interlayer adhesion.

[0012] The core technical solution of this invention lies in: utilizing higher heating temperatures to impart more initial thermal energy to the workpiece, allowing it to naturally cool down to a precise "optimal thermal spraying window" (65-80°C) after transfer. Powder coating is then performed at this temperature, where the powder melts rapidly upon contact with the workpiece, reducing viscosity and significantly enhancing fluidity (leveling properties), using an ultra-high solids formulation. Its function is to form an ultra-thick paint film through a single coating, utilizing the gravity-induced leveling effect and extremely low curing shrinkage of the thick film to physically fill and cover any microscopic unevenness that may remain in the underlying layer, achieving ultimate smoothness for the optical mirror surface.

[0013] The specific solution of the present invention is as follows: A method for improving orange peel texture in aluminum alloy wheel hubs using thermo-electrostatic spraying, the method comprising: S1 Workpiece dehydration heating: Dehydrate and heat the pretreated aluminum alloy wheel hub at a temperature of 150±10℃ for 5 to 10 minutes. S2 thermo-electrostatic spraying black powder: The workpiece treated in S1 is naturally cooled to 65-80℃, and then electrostatic spraying of anti-orange peel black powder is performed at this temperature. Subsequently, it is baked and cured at 180℃ for 8-15 minutes to form a black powder coating. S3 Black Paint Spraying: Preheat the workpiece to 32±8℃, preheat the black paint to 15-30℃, perform electrostatic spraying on the black powder coating formed in S2, and perform leveling and surface drying according to the preset time. S4 Electrostatic Rotary Cup Spraying of High Solids Bright Paint: Maintain the workpiece preheating temperature at 30±10℃, preheat the high solids bright paint to 15-30℃, perform electrostatic rotary cup spraying on the black paint coating after S3 surface drying, and perform leveling and surface drying according to the preset time. S5 Overall Baking and Curing: After completing the black paint and high-solids gloss paint spraying, the entire workpiece is baked and cured at 140℃ for 20-25 minutes.

[0014] Furthermore, the thermal electrostatic spraying black powder in S2 has the following composition by mass percentage: Epoxy resin 40%; polyester resin 40%; filler 14%; additives 5%; pigment 1%; mass deviation of each component is ±8%.

[0015] Furthermore, the process parameters for the thermal electrostatic spraying black powder in S2 are as follows: Atomization pressure 4.5–6.5 m 3 / h; Powder output: 20-35%; Electrostatic current 5–10 μA; Electrostatic high voltage: 55-65KV; Air pressure 0.4~0.7Mpa.

[0016] Furthermore, multiple electrostatic spray guns are used for zoned spraying, with 20-30% powder applied to the front flat area of ​​the wheel hub and 30-35% powder applied to the window, corner and edge areas of the wheel hub.

[0017] Furthermore, the black paint applied in S3 has the following composition by mass percentage: Inorganic pigments 30%; n-butanol 2%; n-butyl acetate 4%; xylene 12%; acrylic resin 38%; amino resin 12%; the mass deviation of each component is ±10%.

[0018] Furthermore, the process parameters for the S3 black paint spraying are as follows: Turbine air pressure: 0.45–0.6 MPa electrostatic current 5–10 μA The coating is applied using a first spray gun with a flow rate of 400–450 cc / min and a second spray gun with a flow rate of 250–300 cc / min.

[0019] Furthermore, the S4 electrostatic rotary cup spraying high-solids gloss paint has the following composition by mass percentage: Leveling agent 3%; n-Butanol 2%; Xylene 17%; Amino resin 15%; Acrylic resin 63%; Mass deviation of each component is ±6%.

[0020] Furthermore, the process parameters for the S4 electrostatic rotary cup spraying of high-solids gloss paint are as follows: Turbine air pressure: 0.45–0.6 MPa electrostatic current 5–10 μA The coating is applied using a first rotary cup spray gun with a flow rate of 380–420 cc / min and a second rotary cup spray gun with a flow rate of 300–350 cc / min.

[0021] further, The thickness of the black powder coating formed by S2 is 110–145 μm; The black paint coating formed by S3 has a thickness of 15–25 μm; The high-solids glossy coating formed by S4 has a thickness ≥40μm.

[0022] Furthermore, during the workpiece spraying process, a protective plug is used at the center cap groove. The protective plug forms a linear contact seal with the edge of the hole on the hub assembly surface through the tapered inclined surface of its head. The cone angle of the tapered surface ranges from 30° to 70°.

[0023] The present invention has the following technical effects: 1. Improved the orange peel appearance of the gloss black wheels. By combining the synergistic effect of "thermal spraying to promote leveling" and "high-solids, high-gloss paint with ultra-thick filling," this invention can reduce the microscopic undulations on the coating surface from a physical perspective. Practical applications show that glossy black wheels produced using this process exhibit significantly improved orange peel texture compared to traditional 20-30℃ room temperature spraying processes, resulting in a deep, smooth, and ripple-free perfect optical mirror finish.

[0024] 2. It breaks through the technical barrier of simultaneously achieving high hardness and high adhesion. By spraying a clear coat onto the black paint while it is only surface dry and curing them together, a strong chemical bond and interpenetrating network are formed between the two coating layers at the interface. The final coating not only has excellent interlayer adhesion but also ensures that the overall coating achieves high hardness, fully meeting the durability and reliability requirements of wheel products.

[0025] 3. It achieves precise and uniform control of film thickness on complex workpieces, thus suppressing orange peel formation at its source.

[0026] By employing a zoned, differentiated parameter electrostatic spraying strategy, compensatory spraying is performed on areas of the wheel hub that are difficult to powder-coated, effectively overcoming the problem of uneven electric field distribution caused by the geometric shape. This significantly improves the overall uniformity of the black powder coating thickness (significantly reducing film thickness difference), ensuring consistent curing shrinkage stress and fundamentally avoiding orange peel defects caused by microscopic film thickness unevenness.

[0027] 4. The process flow has been simplified, reducing production energy consumption and overall costs.

[0028] This invention eliminates the traditional "forced cooling" process and the "spraying transparent powder + 200℃ high-temperature baking" step. This significantly reduces the consumption of electricity and natural gas, aligning with the trend of green manufacturing. Furthermore, the streamlined process directly leads to improved production efficiency and significant economic benefits. For example, for a 17-inch product, the cost per unit is reduced by 3.0 yuan.

[0029] In summary, this invention addresses industry pain points and, through a series of collaborative and innovative technical means, not only effectively solves the orange peel problem of glossy black wheels, but also brings comprehensive and quantifiable positive effects in terms of coating performance, production cost, production efficiency, and green manufacturing. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the actual spraying effect in one embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the spraying effect on a real object as a comparison. Figure 3 This is a schematic diagram of the protective plug structure. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] In this specification, identical components are represented by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "upper," and "lower" used in the following description refer to directions in the accompanying drawings, while the terms "bottom surface," "top surface," "inner," and "outer" refer to directions towards or away from a specific component, respectively. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this specification, "multiple" means two or more.

[0033] Example 1 This invention provides a method for improving orange peel texture in aluminum alloy wheel hubs using thermo-electrostatic spraying. Taking an aluminum alloy wheel hub as an example, the specific implementation process of this invention is demonstrated. The goal is to obtain a deep, high-gloss, orange peel-free glossy black coating on the front of the wheel hub.

[0034] Process: Pre-treatment of workpieces We provide semi-finished aluminum alloy wheels, which undergo standard pre-treatment line operations. The workpieces are sprayed through multiple cleaning tanks for 0.5 to 2 minutes in each tank. This includes pre-degreasing, degreasing, water washing, pickling, water washing, chromium-free passivation, and deionized water rinsing. After these processes, the wheel surface is clean and free of oil and foreign matter.

[0035] Process: Dehydration and heating of the workpiece The workpiece is transferred to a dedicated dehydration heating furnace. This furnace is a natural gas-heated, jacketed combustion chamber connected to a heat exchanger. Its bottom has evenly distributed upward-facing high-speed hot air vents to transfer heat to the workpiece, and the top is equipped with a hydraulically driven, openable, and heat-insulating door. The heating temperature is set to 150±10℃, and the time is set to 5–10 minutes. The wheel hub enters the furnace, with hot air directly blowing onto it from the bottom and circulating from the top, ensuring uniform heating of the entire hub. During the heating process, residual moisture is completely evaporated. After 5–10 minutes, the wheel hub is removed from the furnace and then naturally conveyed and cooled on a conveyor belt.

[0036] Process: Switch lines and assemble universal protective plugs To effectively prevent subsequent coating intrusion, protective plugs are installed on the workpiece, such as... Figure 3 As shown, the protective plug forms a linear contact seal with the edge of the orifice at the center cap groove of the hub through the tapered inclined surface of its head, and the cone angle of the tapered surface ranges from 30° to 70°.

[0037] Process: Thermostatic spraying of anti-orange peel black powder When the wheel hub is transported to the entrance of the sealed powder coating booth, its surface temperature is monitored using an infrared thermometer to confirm that it has stabilized at 65-80℃.

[0038] Powder material: Anti-orange peel black powder is used, and its mass percentage composition is: epoxy resin 40%, polyester resin 40%, filler 14% (such as barium sulfate), additives 5%, pigment 1% (carbon black); the mass deviation of each component is ±8%.

[0039] Spraying equipment: Six automatic electrostatic spray guns are used. The spraying parameters are shown in the table below: Table 1 The spraying process is initiated, with six spray guns working in tandem. Under the influence of a uniform and gentle electrostatic field (high voltage, low current), the powder is evenly adsorbed onto the wheel hub surface at 65–80°C. Due to the high workpiece temperature, the powder melts rapidly upon contact, exhibiting excellent fluidity. After spraying, the sprayed wheel hub is placed in a curing oven and baked at 180°C for 8–15 minutes. The epoxy-polyester resin system fully cross-links and cures, forming a uniform black powder coating with a thickness controlled at 110–145 μm.

[0040] Process: On-line transfer and online polishing After being coated with black powder, the wheel hubs move to the polishing station. The operator uses fine sandpaper (such as P800) to lightly polish only a very small number of particulate impurities or minor runs, and to lightly treat orange peel texture and blemishes.

[0041] Process: Spraying black paint Rotate the wheel hub into the liquid paint spray booth. First, preheat the workpiece to 32±8℃, and preheat the black paint to 15-30℃.

[0042] Black paint material: Its mass percentage composition is as follows: acrylic resin 38%, amino resin 12%, inorganic black pigment 30%, n-butanol 2%, n-butyl acetate 4%, xylene 12%, and other additives 2%; the allowable deviation of the mass of each component is ±10%.

[0043] Spraying equipment: Two suspended cup electrostatic spray guns are used; one for spraying windows and angles, and the other for the main surface. The spray cup rotation speed is controlled by turbine air pressure. Spraying parameters are shown in the table below: Table 2 Two spray guns work together to form a uniform black paint wet film on the wheel hub surface. After spraying, allow 5-10 minutes for leveling and surface drying. During this period, the solvent evaporates, and the surface tension of the paint film allows it to level fully, subsequently reaching a surface-dry state.

[0044] Process: Electrostatic rotary cup spraying of high-solids gloss varnish After the black paint has dried to the touch, immediately apply a high-solids gloss varnish as the process moves on. Maintain the workpiece preheating temperature at 30±10℃, and preheat the high-solids gloss varnish to 15-30℃.

[0045] High-solids glossy paint material: its mass percentage composition is: acrylic resin 63%, amino resin 15%, leveling agent 3%, n-butanol 2%, xylene 17%; the allowable deviation of the mass of each component is ±6%.

[0046] Spraying equipment: Two high-speed rotary cup electrostatic spray guns are used. The spraying parameters are shown in the table below: Table 3 A high-speed rotating spray cup atomizes the paint into extremely fine particles, which are then uniformly adsorbed under the influence of an electrostatic field. The two paint films (black paint and gloss paint) slightly fuse at the interface due to solvent interpenetration. After spraying, the wheel hub undergoes another 5–10 minutes of leveling and surface drying. The gloss paint, with its high solids content and low shrinkage, completes final leveling and reaches surface dryness under gravity and surface tension. The black paint coating thickness is controlled at 15–25 μm, and the high-solids gloss paint coating thickness is ≥40 μm.

[0047] Process: Overall baking and curing After the black paint and high-solids gloss paint are applied, the wheel hub is placed in the final curing oven and baked at 140°C for 20–25 minutes. During this process, the black paint and high-solids gloss paint undergo thorough cross-linking and curing simultaneously as a whole, forming a strong chemical bond and interpenetrating network structure between the two layers.

[0048] Comparative Example 1 To further illustrate the improved effects of the present invention, Comparative Example 1 uses the traditional "powder undercoat + liquid black paint and gloss paint" process to apply a gloss black coating to the same aluminum alloy wheel. The specific process steps are as follows: Dehydration heating and forced cooling: The wheel hub is sent into the oven and dehydrated at 120℃ for 5-10 minutes. After being taken out of the oven, it is immediately placed in a forced cooling chamber and cooled with strong air for 5-6 minutes to reduce the surface temperature of the workpiece to 20-30℃.

[0049] Electrostatic spraying of black powder and curing: Electrostatic spraying is performed using conventional black powder. It is then baked and cured at 180°C for 8–15 minutes.

[0050] After cooling, the obvious orange peel texture and particles on the coating surface are sanded off. Then, regular black paint and regular gloss paint are sprayed in sequence, and baked at 140℃ for 20-25 minutes to cure.

[0051] Test results: Analyzing the thickness of each coating, Table 4 shows that this invention achieves a systematic increase in coating thickness through the combined use of "thermal spraying" and "high-leveling powder." Higher workpiece temperatures (65-80℃) and superior powder leveling properties make it possible and necessary to spray a thicker powder layer. During melting, the thicker powder layer allows for longer internal flow and surface tension interaction, resulting in stronger self-leveling capabilities and providing a significantly smoother "foundation" for subsequent coatings. In the "wet-on-wet" process, the thickened, incompletely cured black paint acts as an "elastic buffer" and "chemical bridge" connecting the underlying powder and the topcoat. Its thickness is sufficient to accommodate slight penetration of the topcoat solvent, promoting interfacial miscibility, but without being too thick to cause sagging or drying problems. The high-solids topcoat, with its 63% acrylic resin content and 15% amino resin, effectively fills in any remaining micron-level unevenness in the underlying black powder and black paint layers from a physical perspective.

[0052] Table 4 In terms of appearance, by Figure 1 , Figure 2 A comparison reveals that the comparative wheel hub exhibits visible, continuously distributed orange peel-like texture on its surface, resulting in poor mirror finish and severe image distortion. Orange peel level measurements using an orange peel meter indicate a grade of 6-7 for this invention, compared to 4-6 for the comparative, a difference of 1-2 grades. The black powder coating shows poor uniformity (large standard deviation). The total coating thickness (thinnest point) differs by ≥57μm, indicating superior corrosion resistance. Regarding surface film hardness and adhesion, the cross-cut adhesion test shows a grade of 0-1, with almost no edge peeling, and a hardness >H.

[0053] In the embodiments disclosed in this application, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; "linking" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments disclosed in this invention according to the specific circumstances.

[0054] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for improving orange peel texture in aluminum alloy wheel hubs using thermo-electrostatic spraying, characterized in that, The method includes: S1 Workpiece dehydration heating: Dehydrate and heat the pretreated aluminum alloy wheel hub at a temperature of 150±10℃ for 5 to 10 minutes. S2 thermo-electrostatic spraying black powder: The workpiece treated in S1 is naturally cooled to 65-80℃, and then electrostatic spraying of anti-orange peel black powder is performed at this temperature. Subsequently, it is baked and cured at 180℃ for 8-15 minutes to form a black powder coating. S3 Black Paint Spraying: Preheat the workpiece to 32±8℃, preheat the black paint to 15-30℃, perform electrostatic spraying on the black powder coating formed in S2, and perform leveling and surface drying according to the preset time. S4 Electrostatic Rotary Cup Spraying of High Solids Bright Paint: Maintain the workpiece preheating temperature at 30±10℃, preheat the high solids bright paint to 15-30℃, perform electrostatic rotary cup spraying on the black paint coating after S3 surface drying, and perform leveling and surface drying according to the preset time. S5 Overall Baking and Curing: After completing the black paint and high-solids gloss paint spraying, the entire workpiece is baked and cured at 140℃ for 20-25 minutes.

2. The method for improving orange peel texture in aluminum alloy wheel hubs using thermo-electrostatic spraying according to claim 1, characterized in that, The thermostatic spraying black powder in S2 has the following composition by mass percentage: Epoxy resin 40%; polyester resin 40%; filler 14%; additives 5%; pigment 1%; mass deviation of each component is ±8%.

3. The method for improving orange peel texture in aluminum alloy wheel hubs using thermo-electrostatic spraying according to claim 1, characterized in that, The process parameters for the thermal electrostatic spraying black powder in S2 are as follows: Atomization pressure 4.5–6.5 m 3 / h; Powder output: 20-35%; Electrostatic current 5–10 μA; Electrostatic high voltage: 55-65KV; Air pressure 0.4~0.7Mpa.

4. The method for improving orange peel texture in aluminum alloy wheel hubs by thermo-electrostatic spraying according to claim 3, characterized in that, Multiple electrostatic spray guns are used for zoned spraying. The powder output is set to 20-30% for the front flat area of ​​the wheel hub, and 30-35% for the window, corner and edge areas of the wheel hub.

5. The method for improving orange peel texture in aluminum alloy wheel hubs using thermo-electrostatic spraying according to claim 1, characterized in that, The black paint applied in S3 has the following composition by mass percentage: Inorganic pigments 30%; n-butanol 2%; n-butyl acetate 4%; xylene 12%; acrylic resin 38%; amino resin 12%; the mass deviation of each component is ±10%.

6. The method for improving orange peel texture in aluminum alloy wheel hubs by thermo-electrostatic spraying according to claim 1, characterized in that, The process parameters for applying black paint using the S3 spraying method are as follows: Turbine air pressure: 0.45–0.6 MPa electrostatic current 5–10 μA The coating is applied using a first spray gun with a flow rate of 400–450 cc / min and a second spray gun with a flow rate of 250–300 cc / min.

7. The method for improving orange peel texture in aluminum alloy wheel hubs using thermo-electrostatic spraying according to claim 1, characterized in that, The S4 electrostatic rotary cup spray high-solids gloss paint has the following composition by mass percentage: Leveling agent 3%; n-Butanol 2%; Xylene 17%; Amino resin 15%; Acrylic resin 63%; Mass deviation of each component is ±6%.

8. The method for improving orange peel texture in aluminum alloy wheel hubs by thermo-electrostatic spraying according to claim 1, characterized in that, The process parameters for applying high-solids gloss paint using the S4 electrostatic rotary cup spraying method are as follows: Turbine air pressure: 0.45–0.6 MPa electrostatic current 5–10 μA The coating is applied using a first rotary cup spray gun with a flow rate of 380–420 cc / min and a second rotary cup spray gun with a flow rate of 300–350 cc / min.

9. The method for improving orange peel texture in aluminum alloy wheel hubs by thermo-electrostatic spraying according to claim 1, characterized in that, The thickness of the black powder coating formed by S2 is 110–145 μm; The black paint coating formed by S3 has a thickness of 15–25 μm; The high-solids glossy coating formed by S4 has a thickness ≥40μm.

10. The method for improving orange peel texture in aluminum alloy wheel hubs by thermo-electrostatic spraying according to claim 1, characterized in that, During the workpiece spraying process, a protective plug is used in the center cap groove. The protective plug forms a linear contact seal with the edge of the hole on the wheel hub assembly surface through the tapered inclined surface of its head. The cone angle of the tapered surface ranges from 30° to 70°.

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