Coating spraying process for aluminum alloy wheel

Abstract

The invention provides a coating spraying process for an aluminum alloy wheel. The coating spraying process comprises the following steps: S1, surface treatment; s2, spraying a bottom coating; s3, spraying a surface coating; s4, spraying a nano-particle reinforcing layer; s5, thermal plasma spraying post-treatment is carried out; according to the process method, the adhesive force can be improved, the cold plasma treatment technology can efficiently activate the surface of the aluminum alloy, the adhesive force between the coating and the base material is enhanced, and the risk that the coating is peeled off is reduced. And by adding the nano-particle reinforcing layer, the surface hardness of the coating is remarkably improved, and the coating has higher scratch resistance. And the corrosion resistance is enhanced, specifically, the corrosion resistance and the ultraviolet resistance of the aluminum alloy wheel are greatly improved through the optimized formula of the bottom coating and the surface coating, especially the application of a nano reinforcing material and a photocureable coating. The ultraviolet curing technology of the photocureable coating greatly shortens the curing time, the high-frequency production requirement is met, and the production efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the surface treatment and coating technology of aluminum alloy wheels, and particularly to a spraying coating process for aluminum alloy wheels using cold plasma, photocurable coatings, nanoparticle reinforced layers, and thermal plasma spraying. Background Art

[0002] As one of the important components in the modern automotive industry, aluminum alloy wheels are widely used in sedans, trucks, SUVs, and other high-performance vehicles due to their light weight, high strength, and good corrosion resistance. The surface coating of aluminum alloy wheels can not only enhance the aesthetics of the wheels but also improve their durability and extend their service life. The surface coating of aluminum alloy wheels usually adopts a spraying process, which can form a thin and uniform coating to provide functions such as anti-corrosion, anti-ultraviolet, and wear resistance.

[0003] However, although the spraying coating of aluminum alloy wheels can improve their surface characteristics, traditional spraying technologies still have some defects. First, traditional spraying technologies usually rely on simple pretreatment methods such as sandblasting and pickling to improve the coating adhesion, but the treatment effects of these methods on the surface of aluminum alloy wheels are limited and often cannot meet the requirements of high-adhesion coatings. In addition, traditional spraying coatings, such as polyester coatings and fluorocarbon coatings, although they can provide good aesthetic effects, their adhesion and corrosion resistance are relatively poor and cannot fully cope with the long-term use of vehicles in harsh environments.

[0004] Currently, some new coating technologies have been applied to the spraying process of wheels in the market, including the use of epoxy resin coatings, ceramic coatings, and powder coatings, etc. Epoxy resin coatings usually have strong adhesion and good corrosion resistance, but their disadvantages are slow curing speed and general performance in anti-ultraviolet and high-temperature resistance. Although ceramic coatings can provide good wear resistance and high-temperature resistance, due to the high hardness of ceramic coatings, it is difficult to achieve uniform coating, and the brittleness of the coating also limits its application.

[0005] In addition, as a relatively advanced coating technology, powder coatings have the advantages of solvent-free, no volatile organic compounds, and good environmental protection. However, due to the high temperature required during the curing process and the usually large coating thickness, it is still difficult to meet the multiple requirements of thin, uniform, and durable coatings for aluminum alloy wheels.

[0006] With the continuous development of technology, the limitations of traditional coating processes have gradually emerged. In order to improve the coating quality and performance of aluminum alloy wheels, researchers and the industrial community have continuously tried to apply new materials and innovative technologies, such as nanotechnology, photocurable coatings, and plasma surface treatment technologies, etc., in order to solve the deficiencies in the existing technologies:

[0007] 1. Applications of nanotechnology: Due to their unique physical and chemical properties, such as a large specific surface area and higher surface energy, nanomaterials have been widely used in coating processes. Nanomaterials can significantly improve the hardness, wear resistance, corrosion resistance, and other properties of coatings. Nano-titanium oxides, nano-silicon materials, and nano-silicon carbide can all be used as reinforcing agents in coatings to improve the overall performance of the coatings. However, how to uniformly disperse these nanoparticles and firmly bond them to the coating matrix remains a technical challenge.

[0008] 2. Applications of cold plasma technology: As a new type of surface treatment technology, cold plasma technology can generate high-energy electrons and ions by exciting gas molecules at room temperature, thereby changing the surface structure of objects and increasing surface energy. When treating the surfaces of materials such as metals and plastics, this technology can effectively improve the adhesion of coatings. In particular, for metals like aluminum alloys that are difficult to undergo traditional chemical treatments, the application of cold plasma technology has significant advantages.

[0009] 3. Applications of photocurable coatings: Photocurable coatings are coating materials that cure rapidly upon exposure to ultraviolet light. Compared with traditional coatings, photocurable coatings have the advantages of rapid curing, low-temperature curing, solvent-free environmental protection, etc., and can significantly improve production efficiency. Especially in automotive coatings, photocurable coatings can provide good ultraviolet resistance and hardness, and are suitable for coating components with high requirements such as aluminum alloy wheels.

[0010] 4. Applications of thermal plasma spraying technology: Thermal plasma spraying technology sprays coatings onto the surface of workpieces through high-temperature plasmas, and can form uniform and dense coatings. This technology is widely used in metal surface treatment and can significantly improve the adhesion, corrosion resistance, and anti-friction performance of coatings. For the spraying process of aluminum alloy wheels, thermal plasma spraying can effectively improve the problems of uneven coatings and insufficient adhesion existing in traditional spraying technologies.

[0011] Although the above technologies have improved the coating quality of aluminum alloy wheels to a certain extent, the current coating processes still face many challenges, such as thickness control of coatings, uneven adhesion, insufficient corrosion resistance and high-temperature resistance, etc. To overcome these problems, it is necessary to further optimize coating materials, improve spraying technologies, and combine new surface treatment technologies to obtain more excellent coating performance. Summary of the Invention

[0012] Aiming at the above-mentioned existing technical deficiencies, the purpose of the present invention is to provide a spraying coating process for aluminum alloy wheels to improve the coating quality and performance of aluminum alloy wheels.

[0013] To achieve the above purpose, the present invention adopts the following technical solutions:

[0014] An aluminum alloy wheel spraying coating process, comprising the following steps:

[0015] S1. Surface treatment: Using cold plasma technology to perform surface modification on the surface of the aluminum alloy wheel to improve surface energy and increase the adhesion of the coating;

[0016] S2. Primer coating spraying: Mix nano titanium oxide, nano silicon material and modified epoxy resin, and spray it onto the surface of the aluminum alloy wheel by electrostatic spraying process. The thickness of the primer coating is 20 - 40 microns;

[0017] S3. Topcoat spraying: Spray a photocurable coating, the photocurable coating contains a UV initiator and is cured by ultraviolet radiation. The thickness of the coating is 30 - 50 microns;

[0018] S4. Nano - particle reinforced layer spraying: Spray a reinforcing coating containing nano - silicon carbide or nano - aluminum oxide. The thickness of the coating is 10 - 20 microns to improve surface hardness and scratch resistance;

[0019] S5. Thermal plasma spraying post - treatment: Perform thermal plasma spraying treatment on the coating to further enhance the adhesion and corrosion resistance of the coating. The treatment temperature is 800 - 1000 °C and the treatment time is 3 - 5 minutes.

[0020] Preferably, the cold plasma technology uses argon or nitrogen as the treatment gas, and the treatment time is 5 - 10 minutes.

[0021] Preferably, the nano - particle reinforced layer contains a mixture of nano - silicon carbide and nano - aluminum oxide, and the high - pressure air spraying process is used during spraying.

[0022] Preferably, the ultraviolet radiation intensity of the photocurable coating is 200 - 300 mJ / cm 2 , and the irradiation time is 5 - 10 minutes.

[0023] Preferably, the mixture of epoxy resin and nano - material for primer coating spraying is uniformly dispersed by ultrasonic mixing.

[0024] Preferably, the thermal plasma spraying post - treatment uses argon or nitrogen as the medium, the treatment temperature is 900 °C, and the treatment time is 4 minutes.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] Improve adhesion: The cold plasma treatment technology can efficiently activate the aluminum alloy surface, enhance the adhesion between the coating and the substrate, and reduce the risk of coating peeling.

[0027] Enhance wear resistance and hardness: By adding a nano - particle reinforced layer, the surface hardness of the coating is significantly improved, and it has stronger scratch resistance.

[0028] Enhanced corrosion resistance: The optimized formulations of the primer coat and the top coat, especially the application of nano-enhanced materials and UV-curable coatings, greatly improve the corrosion resistance and UV resistance of aluminum alloy wheels.

[0029] Improved production efficiency: The UV curing technology of UV-curable coatings significantly shortens the curing time, meets the high-frequency production requirements, and improves production efficiency. Description of the Drawings

[0030] Figure 1 It is a flow block diagram of the present invention. Detailed Description of the Invention

[0031] The present invention will be further described below with reference to the drawings.

[0032] As Figure 1 shown, a spraying coating process for aluminum alloy wheels, combined with cold plasma surface treatment technology, UV-curable coatings, nano-particle reinforced layers and thermal plasma spraying technology, can effectively improve the adhesion, corrosion resistance, wear resistance and aesthetics of the coatings on aluminum alloy wheels. The following describes the detailed implementation of the present invention through two examples.

[0033] Example 1: Spraying Coating Process for Aluminum Alloy Wheels

[0034] Surface Treatment

[0035] A cold plasma treatment device is used, and nitrogen is selected as the treatment gas. The aluminum alloy wheel is placed in the treatment chamber, and the plasma treatment parameters are set, with the treatment time being 8 minutes. Through the action of cold plasma, the surface of the aluminum alloy wheel is excited to form an activated surface, improving its surface energy and adhesion.

[0036] Primer Coat Spraying

[0037] Nano-titanium oxide, nano-silicon material and epoxy resin are mixed, and an ultrasonic stirring device is used to uniformly mix the materials. The thickness of the primer coat is controlled at 30 microns, and an electrostatic spraying device is used to spray the surface of the wheel.

[0038] After spraying, the wheel is placed in a temperature-controlled drying furnace, the temperature is set at 150 °C, and it is baked for 20 minutes to cure the primer coat and improve its adhesion.

[0039] Top Coat Spraying and UV Curing

[0040] UV-curable coatings are used for top coat spraying, and the coatings mainly contain UV initiators. After spraying is completed, a UV radiation lamp is used for curing, with the UV intensity being 250 mJ / cm 2 , and the irradiation time is 7 minutes. The curing process causes the coating to crosslink rapidly, forming a firm coating.

[0041] Spraying of nanoparticle-reinforced layer

[0042] Prepare a reinforced coating material containing nano silicon carbide and nano aluminum oxide, and spray it using a high-pressure air spraying device. The thickness of the nanoparticle-reinforced layer is controlled at 15 microns. During the spraying process, ensure that the coating evenly covers the surface of the topcoat.

[0043] Post-treatment by thermal plasma spraying

[0044] Put the wheel that has completed the spraying process into a thermal plasma spraying device, use argon as the spraying medium, set the treatment temperature at 900 °C, and the treatment time at 4 minutes. The thermal plasma spraying process effectively enhances the adhesion and corrosion resistance of the coating.

[0045] Finished wheel

[0046] After being processed through the above five steps, the coating of the aluminum alloy wheel has a uniform thickness, and has strong adhesion, wear resistance, corrosion resistance and ultraviolet resistance, and the surface is smooth and beautiful, meeting the quality requirements of high-end automobiles for wheel coatings.

[0047] Example 2: Coating process for aluminum alloy wheels

[0048] Surface treatment

[0049] Use a cold plasma treatment device and select argon as the treatment gas. Put the aluminum alloy wheel into the device, set the treatment time at 10 minutes, and the treatment power at 100 W. Cold plasma treatment can effectively remove the oil stain and oxide layer on the surface of the aluminum alloy, increase the surface energy, and provide a better adhesion basis for the subsequent coating.

[0050] Spraying of primer coat

[0051] Prepare a primer coat material containing nano silicon and modified epoxy resin, and evenly spray the primer coat onto the surface of the aluminum alloy wheel using an electrostatic spraying process. The thickness of the primer coat is 25 microns. After spraying, place it in a drying oven and bake it at a temperature of 180 °C for 15 minutes to ensure that the coating firmly adheres to the wheel surface.

[0052] Spraying of topcoat and ultraviolet curing

[0053] Use a photocurable coating for topcoat spraying, and add an ultraviolet initiator to the coating so that it can quickly cure under ultraviolet irradiation. The ultraviolet radiation intensity is set at 230 mJ / cm 2 , and the irradiation time is set at 6 minutes. Through ultraviolet curing, the coating completes crosslinking in a short time and has good hardness and ultraviolet resistance.

[0054] Spraying of nanoparticle-reinforced layer

[0055] A composite reinforced coating material containing nano-aluminum oxide and nano-silicon carbide is used. The nano-particle reinforced layer is sprayed using a high-pressure air spraying process, and the coating thickness is controlled at 12 microns. The nano-particle reinforced layer can improve the hardness and scratch resistance of the coating and enhance the mechanical properties of the coating.

[0056] Post-treatment by thermal plasma spraying

[0057] The sprayed wheels are subjected to post-treatment by thermal plasma spraying. The treatment temperature is set at 950 °C, the treatment time is 3 minutes, and argon is used as the medium. The thermal plasma spraying process further enhances the corrosion resistance and anti-friction performance of the coating, forming a strong and durable protective layer on the wheel surface.

[0058] Finished wheels

[0059] The coating of the aluminum alloy wheels after the above treatment not only has excellent adhesion, corrosion resistance and wear resistance, but also has a bright and uniform appearance, meeting the requirements of high-end automobiles for wheel coatings. This process can effectively extend the service life of the wheels and improve the appearance quality of the wheels.

[0060] In order to prove that the beneficial effects described in the present invention are indeed achieved, it can be proved through experimental verification and performance comparison in the following aspects:

[0061] 1. Adhesion test

[0062] In the present invention, through the combination of cold plasma surface treatment technology and multi-layer coatings (primer coat, top coat and reinforced layer), the adhesion of the coating on the surface of aluminum alloy wheels is significantly improved. To verify this effect, an adhesion test was carried out, and the adhesion of the coating was measured using the standard "tensile adhesion test" method (such as ASTM D3359 standard).

[0063] Test method: The adhesion of the coating was evaluated by using the tape test method (adhesion test) by drawing grids on the coating surface. During the evaluation, the coating adhesion was classified into 0-5 levels, where level 0 indicates complete peeling and level 5 indicates no peeling of the coating.

[0064] Result: The adhesion of the coating of the aluminum alloy wheels after cold plasma treatment and multi-layer coating combination reached above level 4 (excellent level), which was significantly better than the adhesion of the traditional spraying process (generally at level 2-3).

[0065] Conclusion: Through the improvement of cold plasma treatment and multi-layer coatings, the adhesion between the coating and the surface of aluminum alloy wheels is significantly enhanced, and the durability of the coating is improved.

[0066] 2. Corrosion resistance test

[0067] Corrosion resistance is an important indicator for the coating of aluminum alloy wheels, especially under harsh environments (such as moisture, salt spray, acid and alkali, etc.). To verify the improvement of the process of the present invention in terms of corrosion resistance, a salt spray corrosion test was carried out.

[0068] Test method: According to the ISO 9227 standard, a salt spray corrosion test chamber was used to expose the sprayed aluminum alloy wheels to a 5% salt spray solution at a temperature of 35°C for 1000 hours. During the test, the coating was observed every 250 hours, and the corrosion situation of the coating was recorded.

[0069] Result: The coating of the aluminum alloy wheels treated by the process of the present invention showed excellent corrosion resistance, and no obvious peeling or blistering occurred in the 1000-hour salt spray corrosion test. However, the coating of the aluminum alloy wheels with the traditional spraying process peeled off and corrosion spots appeared after 300 hours.

[0070] Conclusion: By combining cold plasma treatment, nano-particle reinforced layer and ultraviolet curing technology, the corrosion resistance of the coating was greatly improved, and it can effectively meet the usage requirements under harsh environments.

[0071] 3. Wear resistance test

[0072] Aluminum alloy wheels are often exposed to high-friction environments, so the wear resistance of the coating is very crucial. To verify the wear resistance of the coating of the present invention, a standard wear test was carried out.

[0073] Test method: A friction and wear testing machine was used to conduct a wear test on the aluminum alloy wheels according to the ASTM D4060 standard. Under the condition of a standard sandpaper (such as CS-17), a certain pressure and number of friction times were applied to measure the wear amount of the coating.

[0074] Result: The coating of the treated aluminum alloy wheels showed a lower wear amount, and the loss of coating thickness was less than 5% of the original coating thickness, while the wear amount of the traditional coating exceeded 15% of the original coating thickness.

[0075] Conclusion: The spraying coating process of the present invention significantly improved the wear resistance of the coating, enabling the aluminum alloy wheels to have a longer service life during use and better cope with friction damage.

[0076] 4. UV aging resistance test

[0077] When aluminum alloy wheels are exposed to sunlight, the coating is easily affected by ultraviolet rays, resulting in color fading or coating aging. To verify the UV aging resistance of the coating of the present invention, a UV accelerated aging test was carried out.

[0078] Test method: Use a Q-Sun ultraviolet aging test chamber to expose the coating samples to ultraviolet radiation, simulating the aging process of wheels under long-term sunlight exposure. The test conditions are ultraviolet intensity: 1.5 W / m 2 , humidity: 65%, test time: 500 hours.

[0079] Results: After 500 hours of ultraviolet radiation, the coating of the aluminum alloy wheel using the photocurable coating maintains good surface color, without obvious color difference or aging phenomenon. While the traditional coating fades significantly after 200 hours, and there are signs of cracking and aging.

[0080] Conclusion: The ultraviolet anti-aging property of the photocurable coating enables the coating of the present invention to better cope with long-term sunlight exposure and maintain the aesthetics and performance of the coating.

[0081] 5. Comprehensive performance test

[0082] Finally, combining all test results, a comprehensive performance evaluation was carried out to compare the overall performance of the aluminum alloy wheel coatings of the traditional spraying process and the process of the present invention.

[0083] Results: The comprehensive test results show that the process of the present invention is not only superior to the traditional spraying process in terms of adhesion, corrosion resistance, abrasion resistance, ultraviolet anti-aging property, etc., but also the appearance of the coating is smooth and uniform, meeting the aesthetic requirements of high-end cars for wheel coatings.

[0084] Conclusion: Through the above-mentioned multiple tests, the aluminum alloy wheel spraying coating process proposed by the present invention has significant beneficial effects, can significantly improve the comprehensive performance of the coating, extend the service life of aluminum alloy wheels, and meet the technical requirements of the high-end market.

[0085] Summary

[0086] Through experimental tests in multiple aspects such as adhesion, corrosion resistance, abrasion resistance, and ultraviolet anti-aging property, the present invention has demonstrated its excellent effects in improving the quality and performance of aluminum alloy wheel coatings. These experimental data fully verify the effectiveness and feasibility of the technical solution of the present invention, ensuring the realization of the described beneficial effects in practical applications.

Claims

1. An aluminum alloy wheel spraying coating process, characterized in that, It includes the following steps: S1. Surface treatment: Use cold plasma technology to perform surface modification on the surface of the aluminum alloy wheel to increase surface energy and enhance the adhesion of the coating; S2. Primer coating spraying: Mix nano-titanium oxide, nano-silicon material with modified epoxy resin, and spray it onto the surface of the aluminum alloy wheel by electrostatic spraying process. The thickness of the primer coating is 20 - 40 microns; S3. Topcoat spraying: Spray a photocurable coating. The photocurable coating contains a UV initiator and is cured by ultraviolet radiation. The thickness of the coating is 30 - 50 microns; S4. Nano-particle reinforced layer spraying: Spray a reinforced coating containing nano-silicon carbide or nano-aluminum oxide. The thickness of the coating is 10 - 20 microns to improve surface hardness and scratch resistance; S5. Post-treatment by thermal plasma spraying: Perform thermal plasma spraying treatment on the coating to further enhance the adhesion and corrosion resistance of the coating. The treatment temperature is 800 - 1000 °C and the treatment time is 3 - 5 minutes.

2. The spraying coating process for an aluminum alloy wheel according to claim 1, wherein The cold plasma technology uses argon or nitrogen as the treatment gas, and the treatment time is 5 - 10 minutes.

3. The spraying coating process for an aluminum alloy wheel as described in claim 1, characterized in that, The nano-particle reinforced layer contains a mixture of nano-silicon carbide and nano-aluminum oxide, and the high-pressure air spraying process is used during spraying.

4. The spraying coating process of an aluminum alloy wheel according to claim 1, characterized in that, The ultraviolet radiation intensity of the photocurable coating is 200 - 300 mJ / cm 2 , and the irradiation time is 5 - 10 minutes.

5. The spraying coating process for an aluminum alloy wheel according to claim 1, wherein The mixture of epoxy resin and nano-materials for primer coating spraying is evenly dispersed by ultrasonic mixing.

6. The spraying coating process of an aluminum alloy wheel according to claim 1, characterized in that, The post-treatment by thermal plasma spraying uses argon or nitrogen as the medium, the treatment temperature is 900 °C, and the treatment time is 4 minutes.

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