3c2b high-gloss mirror silver coating for wheel hub and preparation method and application thereof

Abstract

This invention discloses a 3C2B high-gloss mirror silver coating for wheel hubs, its preparation method, and its application, relating to the field of coating technology. The coating comprises the following raw materials in parts by weight: 45-52 parts of a special acrylic polyurethane monomer resin, 37-44 parts of a composite solvent, 0.01-0.02 parts of a leveling agent, 10-13 parts of mirror silver aluminum powder, and 0.3-0.6 parts of a dispersant. The composite solvent is prepared from butyl acetate, isobutyl ketone, and isobutyl isobutyrate in a mass ratio of 22-26:9-11:6-7. The introduction of the composite solvent, the special acrylic polyurethane monomer resin, and the mirror silver aluminum powder with a specific particle size in this invention simultaneously improves gloss, PVD coating repair compatibility, and 3C2B mass production process compatibility. Therefore, the 3C2B high-gloss mirror silver coating of this invention has a wider application prospect in the field of PVD wheel hub and rim repair without defects.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a 3C2B high-gloss mirror silver coating for wheel hubs, its preparation method, and its application. Background Technology

[0002] With the continuous upgrading of the quality of high-end automotive interiors and exteriors, high-gloss mirror-finish wheels, with their exquisite and transparent metallic texture and high-end minimalist visual effect, have become a mainstream configuration for luxury passenger vehicles. The market has increasingly stringent requirements for the gloss, smoothness, and process compatibility of wheel mirror coatings. Currently, physical vapor deposition (PVD) technology, with its ultra-high mirror clarity and uniform metallic luster, is widely used in the mass production of high-end wheels, and the appearance and texture of the finished wheels far surpasses that of traditional electroplated products. However, the surface coating of PVD wheels has low hardness, making them prone to damage such as bumps, scratches, and wear during use. Moreover, there is currently no suitable dedicated repair coating in the industry. After damage, repairs result in large color differences, severe loss of gloss, and abrupt repair boundaries, significantly reducing the aesthetics of the finished wheel. This leads to high product scrap rates and after-sales repair rates, hindering the industrialization and promotion of high-end PVD wheels.

[0003] Currently, conventional electroplated silver coatings are commonly used for wheel rim mirror repair. These coatings are mostly made of ordinary acrylic and polyester resins as the main film-forming components, combined with conventional mixed solvents and 5-10μm large-particle-size aluminum powder. They are only suitable for simple two-coat two-bake (2C2B) and two-coat one-bake (2C1B) coating processes. Conventional electroplated silver coatings have significant shortcomings in their own system. After spraying and curing, the gloss of the paint film is only 100-120 GU, resulting in poor mirror reflection and failing to meet the appearance requirements of high-end wheel rims with ultra-bright mirror finishes. At the same time, this coating system has extremely poor compatibility with PVD coatings, with significant differences in curing shrinkage and paint film distribution characteristics. When used for PVD wheel rim repair, it is prone to problems such as insufficient adhesion, color deviation, and localized loss of gloss, failing to achieve a seamless repair effect.

[0004] In addition, existing electroplated silver coatings are not compatible with the mainstream three-coat two-bake (3C2B) process for high-end wheel mass production. Under wet-on-wet multi-layer spraying and secondary baking conditions, coating defects such as clear coat and color coat adhesion, loss of paint film texture, orange peel effect, and numerous pinholes are easily encountered, resulting in extremely poor process compatibility and construction stability. The reason for this is that traditional resins have insufficient wetting properties, which cannot achieve dense directional arrangement of aluminum powder. Furthermore, the solvent evaporation gradient and the leveling aid have poor compatibility with the system. After high-temperature baking, the smoothness and metallic texture of the paint film are significantly reduced, making it difficult to meet both mass production process requirements and mirror-like appearance standards.

[0005] Therefore, developing a high-gloss mirror silver coating that is compatible with the 3C2B coating process and can achieve seamless repair of PVD wheel hubs is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a 3C2B high-gloss mirror silver coating for wheel hubs, its preparation method, and its application, thereby solving the following technical problems:

[0007] Existing wheel hub electroplating silver coatings still suffer from problems such as insufficient gloss, poor compatibility with PVD coating repairs, incompatibility with 3C2B mass production processes, and numerous construction defects.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] A 3C2B high-gloss mirror silver coating for wheel hubs comprises the following raw materials in parts by weight: 45-52 parts of special acrylic polyurethane monomer resin, 37-44 parts of composite solvent, 0.01-0.02 parts of leveling agent, 10-13 parts of mirror silver aluminum powder, and 0.3-0.6 parts of dispersant.

[0010] Preferably, the composite solvent is made of butyl acetate solvent, isobutyl ketone solvent, and isobutyl isobutyrate in a mass ratio of 22-26:9-11:6-7.

[0011] The butyl acetate solvent is either butyl acetate or isobutyl acetate;

[0012] The isobutyl ketone solvent is either methyl isobutyl ketone or diisobutyl ketone.

[0013] Preferably, the leveling agent is a polyether-modified siloxane leveling agent.

[0014] Preferably, 0.3-0.8 parts by weight of aluminum powder orientation aligning agent may be added to the 3C2B high-gloss mirror silver coating for the wheel hub;

[0015] The aluminum powder orientation accelerator is cellulose acetate butyrate.

[0016] Preferably, the particle size of the mirror silver aluminum powder is 2μm.

[0017] Preferably, the wheel hub has a mirror gloss of 212-228 GU after being sprayed with 3C2B high-gloss mirror silver coating, a coating adhesion of grade 0, an orange peel grade of grade 1, and a DOI value of 92.5-95.8.

[0018] A method for preparing a 3C2B high-gloss mirror silver coating for wheel hubs includes the following steps:

[0019] Add a special acrylic polyurethane monomer resin to the mixed solvent and stir until transparent. Then add a leveling agent and a dispersant and stir for 10-15 minutes. Then add mirror silver aluminum powder and disperse for 15-20 minutes to obtain a mirror silver coating.

[0020] The beneficial effects of this invention are:

[0021] This invention provides a 3C2B high-gloss mirror silver coating for wheel hubs, its preparation method, and its application. Through a synergistic design using a special acrylic polyurethane monomer resin system, ultrafine mirror silver powder combined with directional additives, and a gradient-compounded mixed solvent, it specifically addresses industry pain points such as insufficient gloss in existing electroplated silver coatings, poor compatibility with PVD coating repair, incompatibility with 3C2B mass production processes, numerous construction defects, and weak protective performance. It achieves a dual breakthrough in high-end PVD wheel hub seamless repair and mass production coating performance. Specific beneficial effects are as follows:

[0022] (I) This invention uses a special acrylic polyurethane monomer resin as the core film-forming body, replacing traditional ordinary acrylic and polyester resins. The resin molecular chain segments are rich in polar active groups, possessing excellent flexibility, cross-linking density, and substrate wettability. This resin can tightly bond with the microstructure of the PVD coating surface, completely solving the problems of poor compatibility and weak interlayer adhesion between traditional coatings and PVD coatings. Tests show that the interlayer adhesion can reach level 0, with no peeling or flaking defects. At the same time, this resin has excellent high-temperature baking stability and can be adapted to the 3C2B three-coat two-bake process for wheel mass production. It can withstand multiple high-temperature baking and wet-on-wet multi-layer spraying conditions, effectively avoiding coating defects such as clear coat bleeding, loss of paint film texture, blooming, orange peel, and pinholes that are common in traditional coatings, greatly improving the stability of mass production construction and process compatibility. Compared with the ordinary acrylic resin system of Comparative Example 1, the resin system of this invention completely solves the core problems of poor adhesion, significant reduction in sharpness, and weak protective performance, laying the foundation for long-term stable adhesion of mirror coatings.

[0023] (II) This invention precisely selects 2μm ultrafine special mirror silver aluminum powder, combined with cellulose acetate butyrate directional alignment additives, to achieve a single-layer, parallel, and dense directional arrangement of aluminum powder particles within the paint film, without stacking or disordered agglomeration, maximizing the light reflectivity of the paint film and giving the coating an ultra-high mirror gloss effect. The mirror gloss level of this invention can reach 212-228 GU, far exceeding the 100-120 GU gloss level of traditional electroplated silver coatings. Simultaneously, the orange peel grade of the paint film is as low as level 1, and the DOI image clarity can reach 92.5-95.8. The paint surface is smooth and transparent, with an ultimate mirror texture, perfectly matching the ultra-bright mirror appearance standards of high-end PVD wheel hubs. Compared to the large-particle-size aluminum powders in Comparative Examples 2 and 3, the ordinary aluminum powder in Comparative Example 4, and the conventional electroplating silver powder in Comparative Example 5, the combination of ultrafine mirror silver powder and directional additives in this invention can completely avoid the problems of messy aluminum powder distribution, uneven reflection, and rough and foggy paint surface, and achieve a high-end mirror visual effect upgrade from the pigment system level.

[0024] (III) This invention employs a multi-component gradient mixed solvent system composed of butyl acetate, methyl isobutyl ketone, and isobutyl isobutyrate, with a scientifically proportioned ratio of high and low boiling point solvents, exhibiting gradient evaporation characteristics. The low-boiling-point solvent can evaporate and set quickly, avoiding wet film sagging and pigment sedimentation; the high-boiling-point solvent can moderately extend the leveling window of the paint film, assisting in the full spreading of the resin and the precise orientation of the aluminum powder, effectively improving the smoothness and gloss uniformity of the paint film. At the same time, the multi-component mixed solvent has excellent solubility and dispersibility for special acrylic polyurethane resins, additives, and mirror silver powder, with good system storage stability, uniform spray atomization, and no particle or pinhole defects. Compared with single solvents, binary solvents, and solvent systems with unbalanced ratios, the solvent system of this invention is perfectly compatible with the 3C2B wet-on-wet spraying process, completely solving problems such as orange peel, gloss decay, and poor interlayer compatibility caused by uneven solvent evaporation, while taking into account both workability and finished product appearance quality.

[0025] (iv) The resin, pigment, solvent, and additive system of this invention exhibits a high degree of synergy, resulting in a dense and uniform cross-linked structure in the molded paint film. This effectively blocks moisture and salt spray erosion, providing excellent salt spray protection. After 480 hours of continuous salt spray testing, the scratch spread length of the example sample was only 0.4-0.7 mm, demonstrating protective performance far exceeding that of various comparative systems. This effectively extends the service life of the PVD wheel hub repair area, preventing corrosion, loss of gloss, and damage from occurring preferentially at the repair site, thus solving the problems of poor protection and high rework rate of traditional repair coatings. Furthermore, the system's formulation is scientifically and rationally proportioned, achieving high gloss, high adhesion, high reflectivity, and excellent protection without the need for additional functional additives. The construction process is simple, and it is highly adaptable to mass production, significantly reducing the scrap rate and production cost of PVD wheel hub repairs.

[0026] (V) This invention can achieve a seamless repair effect for PVD wheels. The repaired area has a high degree of uniformity in gloss, texture, and color with the original PVD coating, with no obvious color difference, loss of gloss, or abrupt boundary issues. The overall appearance of the repaired wheel is extremely consistent. At the same time, it is perfectly compatible with the industry's mainstream 3C2B mass production coating process. It is suitable for seamless repair of damaged wheels after sales, as well as for mass production coating of high-end mirror wheels. It has a wide range of applications and effectively breaks through the technical bottleneck that traditional electroplated silver coatings cannot simultaneously achieve a high-end mirror appearance and the stability of mass production processes, thus helping the industrialization and large-scale promotion of high-end PVD wheels.

[0027] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The embodiments described below are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Unless otherwise specified, the following information pertains to some of the raw materials used in the following embodiments and comparative examples of this invention:

[0030] Special acrylic polyurethane monomer resin, model: EDL-MA521; mirror silver aluminum powder with a particle size of 2μm, purchased from Shenzhen Caidie Technology Co., Ltd., model: D-136; aluminum powder orientation aligning agent is cellulose acetate butyrate, model: Eastman CAB-381-20.

[0031] Example 1: A method for preparing a 3C2B high-gloss mirror silver coating for wheel hubs is as follows:

[0032] Add 45g of special acrylic polyurethane monomer resin to a mixed solvent of 22g butyl acetate, 9g methyl isobutyl ketone, and 6g isobutyl isobutyrate and stir until transparent. Then add 0.01g leveling agent BYK-320 and 0.3g dispersant BYK-104S and stir for 10min. Then add 10g mirror silver aluminum powder (model: D-136) with a particle size of 2μm and 0.3g aluminum powder orientation agent and disperse for 15min to obtain mirror silver coating.

[0033] Example 2: A method for preparing a 3C2B high-gloss mirror silver coating for wheel hubs is as follows:

[0034] In a mixed solvent of 24g butyl acetate, 10g methyl isobutyl ketone, and 6.5g isobutyl isobutyrate, 48.5g of special acrylic polyurethane monomer resin was added and stirred until transparent. Then, 0.015g of leveling agent BYK-320 and 0.45g of dispersant BYK-104S were added and stirred for 18min. Then, 11.5g of mirror silver aluminum powder (model: D-136) with a particle size of 2μm and 0.5g of aluminum powder orientation agent were added and dispersed for 18min to obtain mirror silver coating.

[0035] Example 3: A method for preparing a 3C2B high-gloss mirror silver coating for wheel hubs is as follows:

[0036] Add 52g of special acrylic polyurethane monomer resin to a mixed solvent of 26g isobutyl acetate, 11g diisobutyl ketone, and 7g isobutyl isobutyrate, and stir until transparent. Then add 0.02g leveling agent BYK-333 and 0.6g dispersant BYK-104S and stir for 15min. Then add 13g mirror silver aluminum powder (model: D-136) with a particle size of 2μm and 0.8g aluminum powder orientation agent and disperse for 20min to obtain mirror silver coating.

[0037] Comparative Example 1:

[0038] Compared with Example 1, this comparative example only replaces the "special acrylic polyurethane monomer resin" added during the preparation process with "acrylic resin". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, a 3C2B high-gloss mirror silver coating for wheel hubs is obtained.

[0039] Comparative Example 2:

[0040] Compared with Example 1, this comparative example only replaces the "2μm particle size mirror silver aluminum powder (model: D-136)" added during the preparation process with "7μm particle size mirror silver aluminum powder (model: Decomet Highgloss VP / 13302)". All other steps and parameters are the same, and will not be repeated in this comparative example. The final result is 3C2B high gloss mirror silver coating for wheel hubs.

[0041] Comparative Example 3:

[0042] Compared with Example 1, this comparative example only replaces the "2μm particle size mirror silver aluminum powder (model: D-136)" added during the preparation process with "7μm particle size mirror silver aluminum powder (model: METALURE L-51007 MA)". All other steps and parameters are the same, and will not be repeated in this comparative example. The final result is 3C2B high gloss mirror silver coating for wheel hubs.

[0043] Comparative Example 4:

[0044] Compared with Example 1, this comparative example only replaces the "mirror silver aluminum powder (model: D-136) with 2μm particle size" added during the preparation process with "aluminum powder with 2μm particle size". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, 3C2B high gloss mirror silver coating for wheel hubs is obtained.

[0045] Comparative Example 5:

[0046] Compared with Example 1, this comparative example only replaces the "mirror silver aluminum powder (model: D-136) with 2μm particle size" added during the preparation process with "electroplated silver powder with 2μm particle size". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, 3C2B high gloss mirror silver coating for wheel hubs is obtained.

[0047] Comparative Example 6:

[0048] Compared with Example 1, this comparative example only replaces the "mixed solvent of 22g butyl acetate, 9g methyl isobutyl ketone and 6g isobutyl isobutyrate" with "37g butyl acetate" during the preparation process. All other steps and parameters are the same, and will not be repeated in this comparative example. The final product is 3C2B high-gloss mirror silver coating for wheel hubs.

[0049] Comparative Example 7:

[0050] Compared with Example 1, this comparative example only replaces the "mixed solvent of 22g butyl acetate, 9g methyl isobutyl ketone and 6g isobutyl isobutyrate" with "22g butyl acetate and 15g methyl isobutyl ketone". All other steps and parameters are the same, and will not be repeated in this comparative example. The final product is 3C2B high-gloss mirror silver coating for wheel hubs.

[0051] Comparative Example 8:

[0052] Compared with Example 1, this comparative example only replaces the "mixed solvent of 22g butyl acetate, 9g methyl isobutyl ketone and 6g isobutyl isobutyrate" added during the preparation process with "22g butyl acetate and 15g isobutyl isobutyrate". All other steps and parameters are the same, and will not be repeated in this comparative example. The final product is 3C2B high-gloss mirror silver coating for wheel hubs.

[0053] Comparative Example 9:

[0054] Compared with Example 1, this comparative example only replaces the "mixed solvent of 22g butyl acetate, 9g methyl isobutyl ketone, and 6g isobutyl isobutyrate" added during the preparation process with "22g butyl acetate, 6g methyl isobutyl ketone, and 9g isobutyl isobutyrate". All other steps and parameters are the same, and will not be repeated in this comparative example. The final product is 3C2B high-gloss mirror silver coating for wheel hubs.

[0055] Performance testing:

[0056] The PVD rim was partially polished, cleaned, and dried. Then, the sample was prepared according to the standard 3C2B process for wheel hubs (first, a high-gloss mirror primer was sprayed and baked for the first time, then a 1μm thick mirror silver coating prepared in proportion according to the embodiment of the present invention was sprayed and flash-dried for 8 minutes, then a clear coat was sprayed and baked for the second time). After cooling, the sample was obtained.

[0057] Measurement of specular gloss:

[0058] Referring to the GB / T 9754-2025 standard, the specular gloss of 20° was measured using a gloss meter under constant temperature and humidity GB / T9278 standard environment. The test results are shown in Table 1.

[0059] Adhesion determination:

[0060] Referring to GB / T 34681-2017 and GB / T 9286-2021 standards, the complete 3C2B coating of aluminum alloy was partially polished, and then the mirror silver coating prepared by the various embodiments and comparative examples of the present invention was sprayed and baked. The interlayer adhesion was then measured, and the test results are shown in Table 1.

[0061] Determination of vividness:

[0062] Referring to the GB / T 35236-2017 standard, the sample was scanned using an orange peel and DOI (reflective image clarity) tester, and the orange peel grade and DOI value were recorded. The higher the DOI and the lower the orange peel grade, the better the leveling and smoothness of the paint film. The test results are shown in Table 1.

[0063] Salt spray resistance test:

[0064] The sample was sealed with epoxy putty, and the areas with mirror silver coating were marked. After soaking in 5% sodium chloride solution for 7 days, it was placed in a salt spray test chamber and subjected to 480 hours of continuous salt spray at 35℃ using a 5% sodium chloride solution with a pH of 6.5-7.2 (salt spray deposition rate of 2 mL / (80 cm²)). 2 After treatment, the length of the scribe line spread (mm) was measured. The test results are shown in Table 1.

[0065] Table 1: Performance test results of Examples 1-3 and Comparative Examples 1-9

[0066]

[0067] Data Analysis:

[0068] As can be clearly seen from the performance test data in Table 1, the 3C2B high-gloss mirror silver coating for wheel hubs prepared in Examples 1-3 of this invention exhibits excellent performance in four core properties: mirror gloss, interlayer adhesion, paint film clarity, and salt spray resistance. All indicators are superior to all comparative samples, simultaneously meeting the core requirements of high-end PVD wheel hub seamless repair, 3C2B mass production process compatibility, ultra-high mirror appearance, and long-term protection. Its overall performance is balanced and outstanding. Each comparative sample showed varying degrees of performance degradation by replacing the core resin, aluminum powder type, solvent system, and adjusting the solvent ratio. Specific data analysis is as follows:

[0069] Comparative Example 1 replaced the special acrylic polyurethane monomer resin of this invention with an equal amount of ordinary acrylic resin. Compared with Example 1, all properties were significantly reduced. The mirror gloss was only 116 GU, the interlayer adhesion dropped to level 3, the orange peel grade deteriorated to level 4, the DOI value was only 61.3, and the 480h salt spray scratch propagation length was as high as 3.6 mm. This may be because ordinary acrylic resin has low crosslinking density and poor high-temperature stability, making it unsuitable for the 3C2B multiple baking process. The paint film is prone to thermal deformation and leveling failure. At the same time, the resin has extremely poor wettability and adhesion to the PVD coating, making it prone to peeling between layers. It also cannot effectively bind the aluminum powder to oriented arrangement, resulting in disordered pigment distribution and a significant decrease in light reflectivity. Ultimately, this leads to a dull paint surface, severe orange peel, complete loss of mirror texture, and high porosity of the paint film, making it extremely easy for salt spray to penetrate and corrode, resulting in complete failure of protective performance. It is completely unable to meet the needs of high-end wheel coating and repair.

[0070] In Comparative Examples 2 and 3, the 2μm ultrafine mirror silver aluminum powder was replaced with two types of 7μm large-particle-size aluminum powder, respectively. Compared with Example 1, the overall performance deteriorated. The mirror gloss decreased to 143GU and 168GU, respectively; the adhesion decreased to level 1; the orange peel grade increased to level 3-5; the DOI value decreased significantly; and the salt spray erosion length increased significantly. This may be because the aluminum powder particle size is too large, resulting in a large microscopic unevenness on the paint film surface after spraying and forming, which makes it impossible to form a smooth mirror structure. This leads to severe light diffuse reflection and a significant reduction in mirror gloss and clarity. At the same time, the large-particle-size aluminum powder has a large self-weight, which makes it easy to settle and stack during the paint film curing process, making it impossible to achieve uniform directional distribution. This results in a rough paint surface, obvious orange peel, and uneven gloss. Furthermore, there are gaps at the interface between the large-particle-size aluminum powder and the resin, which reduces the density of the paint film and allows water vapor and salt spray to easily penetrate, ultimately causing a simultaneous deterioration in both protective performance and appearance.

[0071] Comparative Example 4 was replaced with ordinary 2μm aluminum powder, and Comparative Example 5 was replaced with conventional electroplated silver powder. Compared with Example 1, the mirror gloss, reflectivity, and salt spray resistance all showed a significant decline. The surface smoothness and reflectivity of ordinary aluminum powder and conventional electroplated silver powder were far lower than those of the special mirror silver aluminum powder. In addition, the powder surface activity was poor, and the compatibility with directional additives and resin systems was weak, making it impossible to form a regular mirror reflection coating. The formed paint film was prone to problems such as fogging and dull gloss. At the same time, the powder dispersion uniformity was insufficient, and local agglomeration was prone to occur, resulting in uneven paint texture. Furthermore, the coating density was insufficient, and the corrosion protection ability was significantly weakened. It could only meet the needs of ordinary wheel hub coating and could not be adapted to the repair and mass production standards of high-end PVD mirror wheel hubs.

[0072] Comparative Example 6 used a single butyl acetate solvent system, completely disrupting the gradient evaporation balance. Compared with Example 1, gloss, sharpness, and salt spray resistance all decreased significantly, and the orange peel grade increased to level 5. This may be because the single solvent had a uniform evaporation rate, resulting in excessively rapid solvent evaporation during the flash-drying stage. Insufficient leveling time meant that the aluminum powder did not complete its directional arrangement before setting, leading to poor surface smoothness, severe orange peel, and low gloss. Simultaneously, the solvent's limited dissolving and dispersing ability made the system prone to uneven powder dispersion, reducing the uniformity and density of the paint film, thereby lowering the coating's protective performance and appearance quality.

[0073] Comparative Examples 7 and 8 used a binary mixed solvent system, lacking the key components isobutyl isobutyrate and methyl isobutyl ketone. This resulted in an unbalanced solvent evaporation gradient, leading to a slight deterioration in various properties compared to Example 1, with an increased orange peel effect, decreased DOI value, and increased salt spray erosion length. This may be due to the unreasonable combination of high and low boiling points in the binary solvent system, resulting in uneven evaporation rates during wet film formation, which easily leads to localized dry spraying and insufficient leveling. This also slightly disrupts the directional distribution of aluminum powder, causing a decrease in the smoothness and gloss uniformity of the paint surface. Simultaneously, the solvent weakens the dispersion stability of the resin and powder, reducing the microstructure density of the paint film and consequently reducing its salt spray protection performance.

[0074] Comparative Example 9, by adjusting the ternary solvent ratio and disrupting the optimal ratio balance, showed a slight deterioration in mirror gloss, reflectivity, and protective performance compared to Example 1. This may be because the imbalanced solvent ratio led to a disordered gradient evaporation rhythm, a decrease in the matching degree of evaporation of high and low boiling point solvents, and an inability to accurately adapt to the leveling and setting rhythm of 3C2B wet-on-wet spraying. The directional alignment effect of aluminum powder was slightly affected, resulting in a slight decrease in the mirror texture and smoothness of the paint surface. At the same time, the uniformity of paint film formation deteriorated, and the protective performance was slightly reduced.

[0075] Comprehensive test data shows that this invention achieves a synergistic coating system through the precise formulation of a special acrylic polyurethane monomer resin, 2μm ultrafine mirror silver powder + directional additives, and a ternary gradient compound solvent. All three components are indispensable and optimally proportioned, simultaneously achieving ultra-high mirror gloss, excellent interlayer adhesion, exceptional paint reflectivity, and long-lasting corrosion resistance. This perfectly adapts to the 3C2B mass production coating process for wheels and the seamless repair scenario for PVD wheels. All comparative examples, which only modified a single core component or proportion, resulted in degradation of multiple indicators in appearance, process compatibility, and protective performance. This fully demonstrates the scientific nature and uniqueness of the formulation system of this invention, effectively solving various technical shortcomings of traditional mirror silver coatings and significantly improving the yield rate and repair quality of high-end PVD wheel coatings.

[0076] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A 3C2B high-gloss mirror silver coating for wheel hubs, characterized in that, The raw materials include the following parts by weight: 45-52 parts of special acrylic polyurethane monomer resin, 37-44 parts of composite solvent, 0.01-0.02 parts of leveling agent, 10-13 parts of mirror silver aluminum powder, and 0.3-0.6 parts of dispersant.

2. The 3C2B high-gloss mirror silver coating for wheel hubs according to claim 1, characterized in that, The composite solvent is made of butyl acetate solvent, isobutyl ketone solvent, and isobutyl isobutyrate in a mass ratio of 22-26:9-11:6-7. The butyl acetate solvent is either butyl acetate or isobutyl acetate; The isobutyl ketone solvent is either methyl isobutyl ketone or diisobutyl ketone.

3. The 3C2B high-gloss mirror silver coating for wheel hubs according to claim 1, characterized in that, The leveling agent is a polyether-modified siloxane leveling agent.

4. The 3C2B high-gloss mirror silver coating for wheel hubs according to claim 1, characterized in that, The 3C2B high-gloss mirror silver coating for the wheel hub may also contain 0.3-0.8 parts by weight of aluminum powder orientation aligning agent.

5. The 3C2B high-gloss mirror silver coating for wheel hubs according to claim 1, characterized in that, The particle size of the mirror silver aluminum powder is 2μm.

6. The 3C2B high-gloss mirror silver coating for wheel hubs according to claim 1, characterized in that, The wheel hub, after being coated with 3C2B high-gloss mirror silver paint, has a mirror gloss of 212-228 GU, a coating adhesion grade of 0, an orange peel grade of 1, and a DOI value of 92.5-95.

8.

7. A method for preparing a 3C2B high-gloss mirror silver coating for wheel hubs, characterized in that, Includes the following steps: Add a special acrylic polyurethane monomer resin to the mixed solvent and stir until transparent. Then add a leveling agent and a dispersant and stir for 10-15 minutes. Then add mirror silver aluminum powder and disperse for 15-20 minutes to obtain a mirror silver coating.

8. An application of the 3C2B high-gloss mirror silver coating for wheel hubs according to any one of claims 1-7, characterized in that, The wheel hub is treated with 3C2B high-gloss mirror silver coating for seamless repair of PVD wheel hub rims.

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