Aluminum alloy wheel electroplating strengthening method

Abstract

The invention provides an electroplating strengthening method for an aluminum alloy wheel. The electroplating strengthening method comprises the following steps: forming a periodic microstructure on the surface of the aluminum alloy wheel by utilizing a laser micro-etching technology; immersing the wheel into a supercritical carbon dioxide cleaning system to clean oil stains and oxidation films; after cleaning, spraying an active coating containing nano titanate; a high-compactness plating layer is formed in a pulse current electroplating mode; a chemical nickel-phosphorus plating layer and a hard chromium plating layer containing nano metal particles are sequentially formed on the surface of the wheel; performing hole sealing treatment on the electroplated layer by using low-temperature plasma; and coating and curing a flexible UV coating containing an ultraviolet light absorber on the surface of the electroplated layer to form the anti-aging protective film. According to the invention, a novel double cleaning-activating step is adopted in the pretreatment process, and special pre-plating passivation treatment is combined, so that tight combination of an electroplated layer and an aluminum alloy substrate is ensured, and the adhesive force grade reaches 5B, which is obviously superior to that of a traditional process.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy processing, and specifically to a method for electroplating and strengthening aluminum alloy wheels. Background Art

[0002] Due to their light weight, high strength, strong corrosion resistance, and good thermal conductivity, aluminum alloy wheels are widely used in the automotive industry. However, aluminum alloy materials also have certain problems in actual use, especially in terms of corrosion resistance, wear resistance, and surface aesthetics in harsh environments. Therefore, the modification of their surface properties has become a research hotspot.

[0003] Currently, electroplating is one of the main technical means to improve the surface properties of aluminum alloy wheels. Traditional aluminum alloy electroplating methods usually include steps such as pretreatment, electroplated bottom layer, and surface decorative layer. Among them, pretreatment is an important link to ensure the adhesion of the coating. Conventional treatment methods include pickling, alkaline etching, and oxide film removal, but these methods have the disadvantages of long treatment time, large material loss, and serious environmental pollution. Especially after the treatment of the aluminum alloy surface oxide film, if it is not completely removed, it is extremely easy to cause problems such as peeling of the electroplated layer and poor adhesion.

[0004] In addition, in order to achieve the gloss and durability of the coating, multiple electroplating processes are usually required, which increases the process complexity and cost. At the same time, the chemical reagents used in traditional electroplating processes pose certain hazards to the human body and the environment. In recent years, some studies have tried to improve the above defects by improving the electroplating process or using new electroplating solution formulations, but it is still difficult to achieve a comprehensive improvement in excellent adhesion, corrosion resistance, and other comprehensive properties.

[0005] In summary, for the surface electroplating process of aluminum alloy wheels, a more efficient and environmentally friendly process method is still needed. Summary of the Invention

[0006] Aiming at the above existing technical deficiencies, the purpose of the present invention is to provide a method for electroplating and strengthening aluminum alloy wheels to improve the adhesion, corrosion resistance, and wear resistance of the coating.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A method for electroplating and strengthening aluminum alloy wheels, comprising the following steps:

[0009] S1. Pretreatment process:

[0010] a. Using laser micro-etching technology to form periodic microstructures on the surface of the aluminum alloy wheel, and the size of the microstructures is 5 - 50 μm;

[0011] b. Immersing the wheel in a supercritical carbon dioxide cleaning system to clean the oil stain and oxide film;

[0012] c. Spray an active coating containing nano-titanate after cleaning to form a high-adhesion transition layer;

[0013] S2. Electroplating process:

[0014] a. Adopt pulse current electroplating method and adjust the current density to 1.0 - 5.0 A / dm 2 to form a high-density coating;

[0015] b. Sequentially form an electroless nickel-phosphorus layer and a hard chromium coating containing nano-metal particles on the surface of the wheel, and the total thickness of the coating is 20 - 28 μm;

[0016] S3. Post-treatment process:

[0017] a. Use low-temperature plasma to seal the pores of the electroplated layer;

[0018] b. Coat and cure a flexible UV coating containing an ultraviolet absorber on the surface of the electroplated layer to form an anti-aging protective film.

[0019] Preferably, the scanning speed of the laser micro-etching is 30 - 70 mm / s, and the micro-etching depth is 8 - 15 μm.

[0020] Preferably, the pressure of the supercritical carbon dioxide cleaning is 20 - 35 MPa, the temperature is 35 - 50 °C, and the cleaning time is 10 - 20 minutes.

[0021] Preferably, the period of the pulse current electroplating is 5 - 15 seconds, and the pulse current density changes cyclically between 1.0 - 5.0 A / dm 2 during each cycle.

[0022] Preferably, the thickness of the electroless nickel-phosphorus layer is 5 - 8 μm, and the thickness of the hard chromium coating is 15 - 20 μm.

[0023] Preferably, the power of the plasma sealing treatment is 100 - 200 W, and the treatment time is 3 - 8 minutes.

[0024] Preferably, the curing time of the flexible UV coating is 2 - 5 minutes, and the thickness of the cured coating is 10 - 20 μm.

[0025] Preferably, the hard chromium plating solution used in the electroplating process contains nano-metal particles with a mass fraction of 0.1 - 1.0% to improve the wear resistance and gloss of the coating.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] The present invention ensures a tight bond between the electroplated layer and the aluminum alloy substrate by adopting a novel dual cleaning-activation step in the pretreatment process and combining it with a special pre-plating passivation treatment. The adhesion grade reaches 5B, which is significantly better than the traditional process.

[0028] By selecting optimized electroplating bottom layer materials and post-passivation treatment steps, the present invention greatly improves the corrosion resistance of the electroplated layer, enabling it to withstand a salt spray test for up to 600 hours without obvious corrosion, far exceeding the existing technology level.

[0029] By introducing enhanced nanoparticles during the electroplating process and adopting optimized current density and electroplating solution ratio, the wear amount of the electroplated layer of the present invention is controlled below 5 mg, and the wear resistance is greatly improved, which can significantly extend the service life of aluminum alloy wheels.

[0030] Adopting a novel surface polishing process and a high-gloss electroplating solution formula, the glossiness of the electroplated layer of the present invention can reach above 90 GU, the surface is more bright and beautiful, and the appearance quality of aluminum alloy wheels is significantly improved.

[0031] Through special post-plating passivation and sealing hole treatment, the electroplated layer of the present invention has no cracks and no color change under ultraviolet aging conditions, and has excellent anti-ultraviolet aging performance.

[0032] The present invention adopts an improved cleaning and electroplating solution formula, reduces the use of harmful chemicals, significantly reduces the impact on the environment, and at the same time, the optimized process flow shortens the treatment time and reduces the cost.

[0033] The present invention realizes an overall improvement in the adhesion, corrosion resistance, wear resistance, glossiness and anti-ultraviolet aging performance of the coating. The comprehensive performance is better than the traditional electroplating process and has wide popularization and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flow block diagram of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] The present invention will be further described below with reference to the accompanying drawings.

[0036] As Figure 1 shown, the present invention provides a method for strengthening the electroplating of aluminum alloy wheels, which realizes the efficient strengthening of the surface treatment of aluminum alloy wheels through innovative laser, supercritical, pulse electroplating and plasma-assisted technologies.

[0037] Example 1

[0038] The present invention proposes a method for strengthening the electroplating of aluminum alloy wheels, which specifically includes the following steps:

[0039] (1) Pretreatment process

[0040] 1.1 The surface of the aluminum alloy wheel is treated by a laser micro-etching device with a scanning speed of 50 mm / s and a micro-etching depth of 10 μm to form a periodic micro-structure with a micro-structure size of 10 μm.

[0041] 1.2 The wheel is placed in a supercritical carbon dioxide cleaning system with a cleaning pressure of 30 MPa, a temperature of 40 °C, and a cleaning time of 15 minutes to remove oil stains and oxide films.

[0042] 1.3 A nano-titanate active coating is sprayed on the surface of the cleaned wheel with a coating thickness of 5 μm and dried at 100 °C for 10 minutes to form a high-adhesion transition layer.

[0043] (2) Electroplating process

[0044] 2.1 Using pulse current electroplating technology, a electroless nickel-phosphorus layer is formed on the wheel surface, and the current density varies cyclically between 1.5 A / dm 2 and 3.0 A / dm 2 with a pulse period of 10 seconds and a nickel-phosphorus layer thickness of 6 μm.

[0045] 2.2 Hard chromium electroplating is carried out on the surface of the nickel-phosphorus layer using a plating solution containing nano-aluminum oxide particles (mass fraction 0.5%), with an electroplating current density of 2.5 A / dm 2 , a coating thickness of 18 μm, and a total electroplating time of 40 minutes.

[0046] (3) Post-treatment process

[0047] 3.1 The coating is sealed using low-temperature plasma with a plasma power of 150 W and a treatment time of 5 minutes.

[0048] 3.2 A flexible UV coating containing an ultraviolet absorber is evenly sprayed on the electroplated layer with a curing time of 3 minutes and a coating thickness of 15 μm to form an anti-aging protective film.

[0049] The surface gloss of the treated aluminum alloy wheel reaches over 90 GU, the adhesion reaches 5B, and the corrosion resistance exceeds 500 hours (neutral salt spray test), showing excellent comprehensive performance.

[0050] Example 2

[0051] This example optimizes the process parameters on the basis of Example 1 to further improve the coating performance:

[0052] (1) Pretreatment process

[0053] 1.1 The surface of the aluminum alloy wheel is treated by laser micro-etching technology. The scanning speed is adjusted to 40 mm / s, the micro-etching depth is 12 μm, and regular textures with a micro-structure size of 20 μm are formed.

[0054] 1.2 Immerse the wheel in a supercritical carbon dioxide cleaning system. The cleaning pressure is 25 MPa, the temperature is 45 °C, and the cleaning time is 12 minutes.

[0055] 1.3 Spray an active coating containing nano-zirconia particles on the surface of the cleaned wheel. The coating thickness is 7 μm, and it is dried at 120 °C for 8 minutes.

[0056] (2) Electroplating process

[0057] 2.1 Adopt pulse current electroplating to form a nickel-phosphorus layer on the surface of the wheel. The pulse current density varies between 2.0 A / dm 2 and 4.0 A / dm 2 The pulse period is 8 seconds, and the coating thickness is 7 μm.

[0058] 2.2 In hard chromium electroplating, a plating solution containing nano-silicon carbide particles (mass fraction 0.8%) is used. The electroplating current density is 3.0 A / dm 2 , the coating thickness is 20 μm, and the total electroplating time is 50 minutes.

[0059] (3) Post-treatment process

[0060] 3.1 Through low-temperature plasma sealing treatment, the plasma power is adjusted to 180 W, and the treatment time is 6 minutes.

[0061] 3.2 Coat a flexible UV coating containing a high-efficiency ultraviolet absorber on the surface of the coating. The coating curing time is 4 minutes, and the thickness after curing is 18 μm.

[0062] Experimental verification

[0063] In order to verify the effectiveness and superiority of the aluminum alloy wheel electroplating strengthening method described in the present invention, the following experimental verification was carried out. The test indicators include adhesion, corrosion resistance, wear resistance, glossiness, and ultraviolet aging resistance, etc.

[0064] Experiment 1: Adhesion test

[0065] The cross-cut method in ASTM D3359 standard is used to test the adhesion of the electroplated layer of the aluminum alloy wheel. The results are as follows:

[0066] Sample Number Adhesion Grade Result Description Example 1 of the Present Invention 5B No peeling or falling off Example 2 of the Present Invention 5B No peeling or falling off Comparative Sample 1 3B Partial area peeling Comparative Sample 2 4B Slight peeling at the edge

[0067] The experimental results show that the adhesion of the electroplated layer of the present invention reaches the highest grade (5B), which is better than the comparative sample.

[0068] Experiment 2: Corrosion Resistance Test

[0069] According to the ASTM B117 standard, a neutral salt spray test was conducted to test the corrosion resistance of the coating in a corrosive environment. The test time was 500 hours, and the results are as follows:

[0070] Sample Number Testing Time (h) Surface Corrosion Degree Example 1 of the Present Invention 500 No obvious corrosion Example 2 of the Present Invention 600 No obvious corrosion Comparative Sample 1 300 Large-area corrosion spots appear Comparative Sample 2 400 Slight corrosion at the edge

[0071] The experimental results show that the corrosion resistance of the electroplated coating of the present invention is significantly better than that of the comparative sample.

[0072] Experiment 3: Abrasion Resistance Test

[0073] The abrasion resistance of the electroplated coating was tested using a Taber abrasion tester (H18 grinding wheel, load 1000 g), and the wear amount after 1000 revolutions was recorded. The results are as follows:

[0074] Sample Number Wear Amount (mg) Result Description Example 1 of the Present Invention 5.2 Excellent wear resistance Example 2 of the Present Invention 4.8 Excellent wear resistance Comparative Sample 1 12.5 Serious wear Comparative Sample 2 8.3 Relatively obvious wear

[0075] The experimental results show that the abrasion resistance of the electroplated coating of the present invention has been significantly improved.

[0076] Experiment 4: Glossiness Test

[0077] The glossiness of the coating surface was measured using a glossiness meter (measurement angle 60°). The results are as follows:

[0078] Sample Number Glossiness (GU) Example 1 of the Present Invention 91 Example 2 of the Present Invention 95 Comparative Sample 1 78 Comparative Sample 2 82

[0079] The experimental results show that the coating surface of the present invention has high glossiness and a more beautiful appearance.

[0080] Experiment 5: UV Aging Resistance Test

[0081] An ultraviolet aging test chamber (UV340 lamp tube) was used, with the temperature set at 60 °C and the humidity at 50%. The total test time was 300 hours to evaluate the surface cracks and color change of the coating. The results are as follows:

[0082] Sample Number Testing Time (h) Surface Change Example 1 of the Present Invention 300 No cracks, no color change Example 2 of the Present Invention 300 No cracks, no color change Comparative Sample 1 200 Slight cracks appear Comparative Sample 2 250 Obvious surface color change

[0083] The experimental results show that the electroplated coating of the present invention has excellent stability and durability under ultraviolet aging conditions.

[0084] Summary

[0085] Through the above experimental verification, the electroplating strengthening method for aluminum alloy wheels proposed by the present invention has significantly improved the adhesion, corrosion resistance, abrasion resistance, glossiness and UV aging resistance of the coating, showing excellent comprehensive performance, which proves that the technical solution of the present invention has high practical value and reliability.

Claims

1. An electroplating strengthening method for aluminum alloy wheels, characterized in that, It includes the following steps: S1. Pretreatment process: a. Use laser micro-etching technology to form periodic microstructures on the surface of the aluminum alloy wheel, with the microstructure size being 5 - 50 μm; b. Immerse the wheel in a supercritical carbon dioxide cleaning system to clean the oil stain and oxide film; c. Spray an active coating containing nano-titanate after cleaning to form a high-adhesion transition layer; S2. Electroplating process: a. Adopt pulse current electroplating method to adjust the current density to 1.0 - 5.0 A / dm 2 to form a highly dense coating; b. Sequentially form an electroless nickel-phosphorus layer and a hard chromium coating containing nano-metal particles on the wheel surface, with the total coating thickness being 20 - 28 μm; S3. Post-treatment process: a. Use low-temperature plasma to perform a sealing treatment on the electroplated layer; b. Coat and cure a flexible UV coating containing an ultraviolet absorber on the surface of the electroplated layer to form an anti-aging protective film.

2. The electroplating strengthening method for aluminum alloy wheels according to claim 1, wherein The scanning speed of the laser micro-etching is 30 - 70 mm / s, and the micro-etching depth is 8 - 15 μm.

3. The electroplating strengthening method for aluminum alloy wheels according to claim 1, characterized in that, The pressure of the supercritical carbon dioxide cleaning is 20 - 35 MPa, the temperature is 35 - 50 °C, and the cleaning time is 10 - 20 minutes.

4. The electroplating strengthening method for aluminum alloy wheels according to claim 1, characterized in that, The period of the pulsed current electroplating is 5 - 15 seconds, and the pulsed current density varies cyclically between 1.0 - 5.0 A / dm 2 each time.

5. The electroplating strengthening method for aluminum alloy wheels according to claim 1, characterized in that, The thickness of the electroless nickel-phosphorus layer is 5 - 8 μm, and the thickness of the hard chromium coating is 15 - 20 μm.

6. The electroplating strengthening method for aluminum alloy wheels according to claim 1, characterized in that, The power of the plasma sealing treatment is 100 - 200 W, and the treatment time is 3 - 8 minutes.

7. The electroplating strengthening method for aluminum alloy wheels according to claim 1, characterized in that, The curing time of the flexible UV coating is 2 - 5 minutes, and the coating thickness after curing is 10 - 20 μm.

8. The electroplating strengthening method for aluminum alloy wheels according to claim 1, wherein The hard chromium plating solution used in the electroplating process contains nano-metal particles with a mass fraction of 0.1 - 1.0% to improve the wear resistance and gloss of the coating.

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