A method for improving the bond strength of a coating to an alloy

Abstract

The application discloses a method for improving the bonding strength of coating and alloy, which comprises the following steps: S1, polishing the alloy; S2, immersing the polished alloy into a liquid to perform cavitation treatment on the surface of the alloy; and S3, coating the alloy surface after the cavitation treatment with coating, and drying and curing to obtain the coating. In S2, the liquid can generate hydroxyl radicals during the cavitation treatment. The method can construct a super-hydrophilic surface on the surface of the alloy substrate, and further improve the permeability of the coating and the bonding strength of the coating and the alloy substrate, and has a very wide industrial application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metal material surface treatment, and particularly relates to a method for improving the bonding strength of coating and alloy. BACKGROUND

[0002] Light alloy, mainly refers to three kinds of metals and their alloys, such as aluminum, magnesium and titanium, due to good appearance, high specific strength, small density (aluminum 2.7g / cm 3 , magnesium 1.74g / cm 3 , titanium 4.5g / cm 3 ), easy processing and other characteristics in energy saving and light weight, showing very considerable application prospect. However, light alloy, especially aluminum, magnesium alloy and other materials with high chemical activity and electrode potential, are prone to corrosion in high humidity, salt and alkali environment, not only will cause material failure, cause economic loss, form safety hazard, but also will aggravate environmental pollution. At present, the most commonly used corrosion protection method mainly includes surface strengthening, alloying, surface coating and other methods, among which, coating application is the most economical and practical.

[0003] However, with the increasingly complex service conditions, the requirements for material performance are increasingly strict, and the stability of the coating and the substrate is increasingly strict. The existing coating process solidification, the preparation technology of the coating mainly focuses on the strengthening of the performance of the coating itself, and rarely involves the research on the coating process. Optimizing the coating process, strengthening the substrate alloy, and using high-performance coating can improve the stability of the coating and the substrate, and achieve the effect of 1+1>2. Therefore, it is of great significance to explore a method for improving the coating bonding strength and strengthening the substrate material with low cost, simple process, excellent performance and green environmental protection. SUMMARY

[0004] Based on the above technical problems, the present application provides a method for improving the bonding strength of coating and alloy, which can effectively improve the bonding stability of coating and alloy, and the strength of alloy substrate, and significantly improve the durability of alloy surface coating.

[0005] The specific scheme of the present application is as follows:

[0006] The present application provides a method for improving the bonding strength of coating and alloy, comprising the following steps:

[0007] S1, polishing the alloy; S2, immersing the polished alloy in a liquid to perform cavitation treatment on the surface of the alloy; S3, coating the coating on the surface of the alloy after cavitation treatment, and drying and curing to obtain the coating.

[0008] In S2, the liquid can generate hydroxyl radicals during cavitation treatment.

[0009] Preferably, in S1, the alloy is a light alloy; more preferably, the alloy is at least one selected from an aluminum alloy, a magnesium alloy, and a titanium alloy.

[0010] Preferably, in S1, the roughness of the alloy surface after the polishing treatment is less than or equal to 0.4 μm.

[0011] Preferably, in S2, the liquid is water or an aqueous solution; more preferably, the liquid is an aqueous solution of silicon dioxide.

[0012] Preferably, in S2, the temperature of the liquid is 10-60 °C.

[0013] Preferably, in S2, cavitation treatment is performed using a cavitation treatment device; the vibration head of the cavitation treatment device is immersed in the liquid, and the distance between the vibration head and the surface of the alloy is 0.5-1.2 mm.

[0014] Preferably, in S2, the cavitation treatment device is an ultrasonic vibration device.

[0015] Preferably, in S2, the cavitation treatment parameters are as follows: the amplitude of ultrasonic vibration is 50-100 μm, the frequency of ultrasonic vibration is 20-800 KHz, and the cavitation treatment time is 0.1-2 h.

[0016] Preferably, in S3, the coating treatment is performed on the surface of the alloy within 0-48 h after the cavitation treatment.

[0017] Preferably, in S3, the coating is a water-based coating or a solvent-based coating.

[0018] Preferably, in S3, the coating method is at least one selected from brushing, spraying, and dipping.

[0019] Preferably, in S3, the coating method is selected from ultrasonic dipping and high-pressure spraying.

[0020] The present application has the following advantages:

[0021] The present application provides a method for improving the bonding strength between a coating and an alloy, which has the characteristics of simple operation, safety and reliability, short preparation period, good repeatability, and low cost, can construct a super-hydrophilic surface on the surface of an alloy substrate, thereby improving the permeability of the coating and the bonding strength between the coating and the alloy substrate, and significantly improving the strength of the alloy substrate, and has a very broad industrial application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The present application is a schematic diagram of the operation process.

[0023] Figure 2 The present application is a schematic diagram of the improved ultrasonic vibration device.

[0024] Figure 3Surface morphology of AZ31B magnesium alloy before and after cavitation and the corresponding element content change chart.

[0025] Figure 4 Surface wettability change chart of AZ31B magnesium alloy before and after cavitation.

[0026] Figure 5 Methylene blue content change chart in water solution of AZ31B magnesium alloy before and after cavitation.

[0027] Figure 6 Coating adhesion strength change chart of AZ31B magnesium alloy before and after cavitation.

[0028] Figure 7 Cross-section hardness chart of AZ31B magnesium alloy before and after cavitation.

[0029] Figure 8 Surface morphology of AlSi12 aluminum alloy before and after cavitation and the corresponding element content change chart.

[0030] Figure 9 Surface wettability change chart of AlSi12 aluminum alloy before and after cavitation.

[0031] Figure 10 Coating adhesion strength change chart of AlSi12 aluminum alloy before and after cavitation.

[0032] Figure 11 Cross-section hardness chart of AlSi12 aluminum alloy before and after cavitation.

[0033] Figure 12 Surface wettability change chart of AZ31B magnesium alloy before and after cavitation.

[0034] Figure 13 Coating adhesion strength change chart of AZ31B magnesium alloy before and after cavitation.

[0035] Figure 14 Cross-section hardness chart of AZ31B magnesium alloy before and after cavitation.

[0036] Figure 15 Surface wettability change chart of Ti27Nb alloy before and after cavitation.

[0037] Figure 16 Coating adhesion strength comparison chart of AZ31B magnesium alloy of example 1 and example 5.

[0038] Figure 17 Contact angle change curve of AZ31B magnesium alloy after cavitation of example 1 with time. DETAILED DESCRIPTION

[0039] The application provides a method for improving the bonding strength of a coating and an alloy, comprising the following steps:

[0040] S1, polishing the alloy; S2, immersing the polished alloy into a liquid to perform cavitation treatment on the surface of the alloy; S3, coating the surface of the alloy after the cavitation treatment with a coating, and drying and curing to obtain the coating.

[0041] In S2, the liquid can generate hydroxyl radicals during the cavitation treatment.

[0042] Preferably, in S1, the alloy is a light alloy; more preferably, the alloy is at least one selected from an aluminum alloy, a magnesium alloy and a titanium alloy. The light alloy in the application refers to an alloy material with low density and light weight, which is prone to surface oxidation. Common light alloys include aluminum alloys, magnesium alloys and titanium alloys.

[0043] The application performs cavitation treatment on the polished alloy in the liquid, and a large amount of hydroxyl radicals can be generated. As a strong polar group, the hydroxyl radical is easy to combine with a hydrogen bond and promote the generation of an oxidation layer with a certain thickness on the surface of the alloy, improve the microtopography of the substrate surface, and a large amount of cavitation bubbles broken on the surface of the alloy substrate can introduce dislocations, generate residual compressive stress and work hardening, thereby achieving the effect of strengthening the alloy substrate.

[0044] In addition, the cavitation treatment can also change the wettability of the alloy substrate, and the surface of the alloy substrate after the cavitation treatment is hydrophilic. Under this condition, the coating is coated on the surface of the alloy, which helps to enhance the bonding strength of the coating and the alloy substrate.

[0045] Preferably, in S2, the temperature of the liquid is 10-60℃. Experiments show that the cavitation intensity of the liquid is high between 10-60℃, and further increase of the temperature of the liquid will change the viscosity, surface tension and other factors of the liquid, thereby affecting the cavitation intensity.

[0046] Preferably, in S2, the cavitation treatment parameters are as follows: the ultrasonic vibration amplitude is 50-100μm, the ultrasonic vibration frequency is 20-800KHz, and the cavitation treatment time is 0.1-2h. More preferably, the ultrasonic vibration frequency is 20-30KHz.

[0047] Preferably, in S2, the cavitation treatment is performed by using a cavitation treatment device; the vibration head of the cavitation treatment device is immersed in the liquid, and the distance between the vibration head and the surface of the alloy is 0.5-1.2mm. More preferably, in S2, the cavitation treatment device is an ultrasonic vibration device.

[0048] The cavitation treatment device of the present application refers to a device capable of inducing cavitation. It includes but is not limited to ultrasonic vibration device. Ultrasonic vibration device is a device that uses ultrasonic waves to cause a large number of tiny bubbles (cavitation nuclei) in the liquid to collapse sharply.

[0049] Preferably, in S3, the alloy surface within 0-48h after cavitation treatment is subjected to paint coating treatment.

[0050] Preferably, in S3, the coating method is selected from ultrasonic immersion coating or high-pressure spraying.

[0051] The high-pressure spraying of the present application is a coating process that uses high-pressure equipment to atomize and spray paint onto the surface of the object to be coated; ultrasonic immersion coating is a coating process that uses high-frequency acoustic energy to break down paint molecules to the nanoscale to increase the adhesion of paint to the substrate.

[0052] The present application helps to further enhance the permeability of the paint by ultrasonic immersion coating or high-pressure spraying, to further improve the adhesion strength of the paint to the alloy.

[0053] In order to cooperate with the above method, the present application also provides an improved ultrasonic vibration device as shown in Figure 2 The ultrasonic vibration device comprises: a 4-DOF spherical parallel motion mechanism 1, a variable amplitude rod 2, a rotatable blade 3; the two ends of the variable amplitude rod 2 are connected with the 4-DOF spherical parallel motion mechanism 1 and the rotatable blade 3 respectively, and the bottom of the variable amplitude rod 2 is connected with a vibration head 7; a high-pressure liquid delivery pipe 4 is arranged in the variable amplitude rod 2.

[0054] Preferably, the rotatable blade 3 is controlled to rotate by a motor, and the control rotation speed is 0-50r / s.

[0055] Preferably, the rotatable blade 3 has holes on the surface.

[0056] Preferably, the 4-DOF spherical parallel motion mechanism 1 drives the variable amplitude rod 2 to move in all directions. Its role is to realize the surface modification and coating of materials of different shapes.

[0057] Preferably, the bottom of the high-pressure liquid delivery pipe 4 is provided with an outlet 5, and the outlet 5 is located at the lower end surface of the variable amplitude rod 2.

[0058] Preferably, the vibration head 7 is a hollow structure, the material is hard alloy, the upper end surface is connected with the outlet 5 of the high-pressure liquid delivery pipe 4, and a narrow flow channel 6 is arranged at a distance of 1-4mm from the lower end surface; the diameter of the narrow flow channel is 0.3-0.5mm, and the outlet of the narrow flow channel is located at the lower end surface of the vibration head 7.

[0059] Preferably, the speed of the high-pressure liquid delivery pipe can be controlled within the range of 0-200m / s.

[0060] The high-pressure liquid delivery pipe, the rotatable blade and the amplitude rod can be used alone or in combination according to application scenarios. When used as a paint coating device, the amplitude rod can be used for vibration-assisted coating or the high-pressure liquid delivery pipe can be used for spraying.

[0061] Hereinafter, the technical solutions of the present application will be described in detail through specific examples, but it should be clear that these examples are used for illustration, but not to be interpreted as limiting the scope of the present application.

[0062] Example 1

[0063] A method for improving the bonding strength of paint and alloy, comprising the following steps:

[0064] S1, polishing the surface of AZ31B magnesium alloy, the final surface roughness is 0.1 μm; clean with anhydrous ethanol and dry to remove surface dirt and ash layer;

[0065] S2, immerse the polished AZ31B magnesium alloy into 25℃ distilled water, and use ultrasonic vibration device to perform cavitation treatment on the AZ31B magnesium alloy, the specific parameters are as follows: the vibration head of the ultrasonic vibration device is immersed in the liquid, the distance between the vibration head and the alloy surface is 0.5 mm, the ultrasonic vibration amplitude is 52 μm, the ultrasonic vibration frequency is 20 KHz, and the cavitation treatment time is 0.5 h;

[0066] S3, clean the above treated AZ31B magnesium alloy with anhydrous ethanol to ensure that the dirt on the sample surface is completely removed and dried; then within 48 h after the cavitation treatment, use the high-pressure liquid delivery pipe to spray the anti-corrosion paint on the sample surface at a speed of 6 mm / s; use the oven to heat and cure the sample, the oven temperature is controlled at 60℃, and the drying time is 30 min.

[0067] Test the performance of the AZ31B magnesium alloy before and after cavitation treatment and the AZ31B magnesium alloy coated with paint in S3, and the results are as follows:

[0068] 1、 Figure 3 The figure shows the surface morphology of AZ31B magnesium alloy before and after cavitation and the corresponding change in element content, where before corresponds to the original surface after polishing treatment, and after corresponds to the sample surface after cavitation treatment.

[0069] It can be seen that the surface of the AZ31B magnesium alloy after cavitation treatment has obvious oxidation phenomenon.

[0070] 2、 Figure 4The graph shows the change in surface wettability of AZ31B magnesium alloy before and after cavitation. The "before" graph corresponds to the sample after grinding and polishing treatment, and the "after" graph corresponds to the sample after cavitation treatment (tested immediately after cavitation treatment, within 48 hours).

[0071] It can be seen that after cavitation treatment, the wetting angle of the AZ31B magnesium alloy surface decreased from 85.9° to 4.6°, the wettability was significantly improved, and the sample surface had superhydrophilicity.

[0072] However, after cavitation treatment, the AZ31B magnesium alloy sample was placed for 24 days, and continuous contact angle tests were performed. The contact angle change curve over time is as follows: Figure 17 As shown.

[0073] It can be seen that the wetting angle gradually increases with the increase of the standing time, and the sample surface changes from a superhydrophilic state to a hydrophobic state after the standing time exceeds 2 days. After standing for 21 days, the wetting angle of the AZ31B magnesium alloy surface increases to 150.8°, and the wettability is significantly reduced, exhibiting superhydrophobicity. It is evident that the surface properties of the AZ31B magnesium alloy after cavitation treatment change after a certain period of time, which is not conducive to the bonding of the coating. Therefore, in this invention, S3 coating treatment is performed within 48 hours after cavitation treatment.

[0074] 3. Figure 5 The graph shows the change in methylene blue content in the aqueous solution of AZ31B magnesium alloy before and after cavitation. The "before" corresponds to the sample after polishing, and the "after" corresponds to the sample after cavitation treatment.

[0075] Because hydroxyl radicals are highly reactive and have a short lifespan, they are often indirectly measured by converting them into easily detectable substances. Methylene blue, with its numerous unsaturated double bonds exhibiting strong reducing properties, is frequently used as a hydroxyl radical scavenger. When hydroxyl radicals react with it, the color gradually fades.

[0076] In this experiment, 1000 ml of a 5 mg / L methylene blue solution was prepared by mixing methylene blue with deionized water and used as the medium for ultrasonic cavitation. Based on Lambert-Beer's law, the hydroxyl radical content was determined by measuring the transmittance of the solution at 664 nm (the maximum absorption wavelength of methylene blue) using a UV spectrophotometer after the experiment. A decrease in the transmittance of the solution indicated an increase in the number of hydroxyl radicals participating in the reaction, i.e., an increase in the number of hydroxyl radicals generated during cavitation.

[0077] Depend on Figure 5 It can be seen that the methylene blue reagent content in the aqueous solution of AZ31B magnesium alloy is significantly reduced. Since methylene blue reacts with hydroxyl radicals to form hydroxymethylene blue, this indirectly proves the generation of hydroxyl radicals during cavitation. Furthermore, the number of hydroxyl radicals increases significantly with the increase of ultrasonic cavitation time.

[0078] 4、 Figure 6 The figure of the variation of the bonding strength between AZ31B magnesium alloy and paint before and after cavitation, wherein before corresponds to the sample coated after not being treated by ultrasonic cavitation (i.e. the sample obtained only by S1 and S3 steps), and after corresponds to the AZ31B magnesium alloy coated with paint after S3 cavitation treatment.

[0079] It can be seen that the time and test force used for peeling off the water-based paint after cavitation treatment are obviously greater than those without cavitation treatment, i.e. the bonding strength between AZ31B magnesium alloy and water-based paint is improved by more than 60%.

[0080] 5、 Figure 7 The figure of the cross-section hardness of AZ31B magnesium alloy before and after cavitation, wherein before corresponds to the cross-section hardness of the sample without cavitation treatment, and after corresponds to the cross-section hardness of the AZ31B magnesium alloy after cavitation treatment.

[0081] It can be seen that the surface hardness of AZ31B magnesium alloy is improved after cavitation treatment, and a hardened layer of about 300 μm is formed.

[0082] Example 2

[0083] A method for improving the bonding strength between paint and alloy, comprising the following steps:

[0084] S1, polishing the surface of AlSi12 aluminum alloy to a final surface roughness of 0.1 μm; cleaning with anhydrous ethanol and blowing dry to remove surface dirt and ash layer;

[0085] S2, completely immersing the polished AlSi12 aluminum alloy into 25°C distilled water, and treating the AlSi12 aluminum alloy by cavitation using an ultrasonic vibration device, with the same parameters as those in Example 1;

[0086] S3, cleaning the AlSi12 aluminum alloy treated above with anhydrous ethanol to ensure that the dirt on the surface of the sample is completely removed and dried; then within 48 hours after the end of cavitation treatment, spraying the anticorrosive paint to the surface of the sample through a high-pressure liquid delivery pipe at a spraying speed of 6 mm / s; and using an oven to heat and cure the sample, with the oven temperature controlled at 60°C and the drying time being 30 min.

[0087] The properties of the AlSi12 aluminum alloy before and after cavitation treatment and the AlSi12 aluminum alloy coated with paint in this example were tested, and the results are shown as follows:

[0088] 1、 Figure 8The surface morphology of AlSi12 aluminum alloy before and after cavitation and the corresponding element content change chart, wherein before corresponds to the original surface after polishing treatment, after corresponds to the sample surface after cavitation treatment.

[0089] It can be seen that the surface of AlSi12 aluminum alloy after cavitation treatment has obvious oxidation phenomenon.

[0090] 2、 Figure 9 The surface wettability change chart of AlSi12 aluminum alloy before and after cavitation, wherein before corresponds to the sample after polishing treatment, after corresponds to the sample after cavitation treatment (tested immediately after cavitation treatment, within 48h).

[0091] It can be seen that the surface wettability of AlSi12 aluminum alloy decreases from 66.1° to 9.6° after cavitation treatment, and the wettability is obviously improved, and the sample surface has super hydrophilicity.

[0092] 3、 Figure 10 The bonding strength change chart of AlSi12 aluminum alloy and water-based paint before and after cavitation, wherein before corresponds to the sample coated after ultrasonic cavitation treatment (i.e. the sample obtained only by S1 and S3 steps), after corresponds to the AlSi12 aluminum alloy coated with paint after S1-S3 cavitation treatment.

[0093] It can be seen that the bonding strength of AlSi12 aluminum alloy and water-based paint is improved by more than 50%.

[0094] 4、 Figure 11 The cross-section hardness chart of AlSi12 aluminum alloy before and after cavitation treatment, wherein before corresponds to the cross-section hardness of the sample without cavitation treatment, after corresponds to the cross-section hardness of the AlSi12 aluminum alloy obtained after cavitation treatment.

[0095] It can be seen that the surface hardness of AlSi12 aluminum alloy is improved after cavitation treatment, and a hardened layer of about 325μm is formed.

[0096] Example 3

[0097] A method for improving the bonding strength of paint and alloy, which is different from example 1 only in that (1) the surface roughness after S1 polishing treatment is 0.128μm; (2) the cavitation time in S2 is 0.25h, and the other steps and parameters are the same as example 1.

[0098] The performance of AZ31B magnesium alloy before and after cavitation treatment and S3 coated with paint is tested, and the results are as follows:

[0099] 1、 Figure 12A figure of the surface wettability of AZ31B magnesium alloy before and after cavitation, wherein before corresponds to the sample after polishing treatment, and after corresponds to the sample after cavitation treatment (tested immediately after cavitation treatment, within 48h).

[0100] It can be seen that the surface wettability of AZ31B magnesium alloy is obviously improved after cavitation treatment, and the surface of the sample has super hydrophilicity, with the wettability angle decreasing from 85.9° to 6.6°.

[0101] 2、 Figure 13 A figure of the bonding strength of AZ31B magnesium alloy and water-based paint before and after cavitation, wherein before corresponds to the sample coated after no ultrasonic cavitation treatment (i.e. the sample obtained after only S1 and S3 steps), and after corresponds to the AZ31B magnesium alloy coated with paint after S1-S3 cavitation treatment.

[0102] It can be seen that the time and test force used for peeling off the water-based paint after cavitation treatment are obviously greater than those without cavitation treatment, i.e. the bonding strength of AZ31B magnesium alloy and water-based paint is improved by more than 34%.

[0103] 3、 Figure 14 A figure of the cross-section hardness of AZ31B magnesium alloy before and after cavitation, wherein before corresponds to the cross-section hardness of the sample without cavitation treatment, and after corresponds to the cross-section hardness of AZ31B magnesium alloy after cavitation treatment.

[0104] It can be seen that the surface hardness of AZ31B magnesium alloy is improved after cavitation treatment, and a hardened layer of about 200μm is formed.

[0105] Example 4

[0106] A method for improving the bonding strength of paint and alloy, comprising the following steps:

[0107] S1, polishing treatment is performed on the surface of Ti27Nb alloy, and the final surface roughness is 0.133μm; the Ti27Nb alloy is cleaned with anhydrous ethanol and dried to remove surface oil stains and ash layer;

[0108] S2, the polished Ti27Nb alloy is completely immersed in a 30℃ aqueous silica solution, and cavitation treatment is performed on the Ti27Nb alloy by using an ultrasonic cavitation device, with the following specific parameters: the distance between the ultrasonic cavitation device and the surface of the alloy is 1.0mm, the ultrasonic vibration amplitude is 60μm, the ultrasonic vibration frequency is 28KHz, and the cavitation treatment time is 0.5h;

[0109] S3, using anhydrous ethanol cleaning above the treated Ti27Nb alloy, to ensure that the sample surface stains completely removed and dried; then through the high pressure liquid delivery tube, the corrosion protection paint sprayed to the sample surface, the spray speed 6mm / s; using oven for heat curing, oven temperature control at 60℃, drying time is 30min.

[0110] The performance of Ti27Nb alloy before and after cavitation treatment and the Ti27Nb alloy coated with S3 paint were tested, and the results are shown below:

[0111] 1、 Figure 15 The figure of the change of surface wettability of Ti27Nb alloy before and after cavitation is shown, wherein before corresponds to the sample after polishing treatment, and after corresponds to the sample after cavitation treatment (tested immediately after cavitation treatment, within 48h).

[0112] It can be seen that the surface wettability of Ti27Nb alloy is reduced from 65.6° to 8.9° after cavitation treatment, and the wettability is obviously improved, and the sample surface has super hydrophilicity.

[0113] Example 5

[0114] A method for improving the bonding strength of paint and alloy, which is only different from example 1 in that step S3 adopts roll brush uniform coating of the surface after ultrasonic cavitation, and then placed in a 60℃ oven for 30min.

[0115] The bonding strength of AZ31B magnesium alloy and water-based paint obtained in this example and example 1 is compared, and the comparison chart is shown in Figure 16 It can be seen that the time and test force used for peeling off the water-based paint after high pressure spraying treatment are obviously greater than those of ordinary coating treatment, that is, high pressure spraying treatment can significantly improve the bonding strength of AZ31B magnesium alloy and water-based paint.

[0116] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this, any skilled person in the art can make equivalent replacement or change according to the technical scheme and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A method of improving the bond strength of a coating to an alloy, characterized by, The method comprises the following steps: S1, polishing the alloy; S2, immersing the polished alloy into a liquid to perform cavitation treatment on the surface of the alloy; S3, coating a paint on the surface of the alloy after the cavitation treatment, and drying and curing to obtain the alloy; In S2, the liquid can generate hydroxyl radicals during the cavitation treatment; In S2, the cavitation treatment is performed by using a cavitation treatment device; the vibration head of the cavitation treatment device is immersed in the liquid, and the distance between the vibration head and the surface of the alloy is 0.5-1.2 mm; the cavitation treatment device is an ultrasonic vibration device; the cavitation treatment parameters are as follows: the ultrasonic vibration amplitude is 50-100 μm, the ultrasonic vibration frequency is 20-800 KHz, and the cavitation treatment time is 0.1-2 h.

2. The method of improving paint-to-alloy bond strength according to claim 1, wherein, The alloy is a light alloy.

3. The method of improving paint-to-alloy bond strength according to claim 1, wherein, The alloy is selected from at least one of aluminum alloy, magnesium alloy, and titanium alloy.

4. The method of improving paint-to-alloy bond strength according to claim 1 or 2, wherein In S1, the roughness of the surface of the alloy after the polishing treatment is ≤0.4 μm.

5. The method of improving paint-to-alloy bond strength according to claim 1 or 2, wherein In S2, the liquid is water or an aqueous solution.

6. The method of improving paint-to-alloy bond strength according to claim 1 or 2, wherein In S2, the liquid is an aqueous solution of silicon dioxide.

7. The method of improving paint-to-alloy bond strength according to claim 1 or 2, wherein In S2, the temperature of the liquid is 10-60 ℃.

8. The method of improving paint-to-alloy bond strength according to claim 1 or 2, wherein In S3, the coating treatment on the surface of the alloy is performed within 0-48 h after the cavitation treatment.

9. The method of improving paint-to-alloy bond strength according to claim 1 or 2, wherein In S3, the coating method is at least one of brushing, spraying, and dipping.

10. The method of improving paint-to-alloy bond strength according to claim 1 or 2, wherein The coating method is selected from ultrasonic dipping or high-pressure spraying.

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