Moisture-heat-resistant, corrosion-resistant and mildew-resistant multifunctional coating on magnesium alloy surface as well as preparation and application thereof

Abstract

The invention belongs to the field of magnesium alloy surface treatment, and particularly relates to a magnesium alloy surface damp-heat-resistant, corrosion-resistant and mildew-proof multifunctional coating and preparation and application thereof. The damp-heat-resistant, corrosion-resistant and mildew-proof multifunctional coating on the surface of the magnesium alloy comprises an inner layer and an outer layer, wherein the inner layer is a micro-arc oxidation layer containing Ta, Sn and Sb elements, and the outer layer is an epoxy resin organic coating containing modified conductive mica powder. The multifunctional coating is used for improving the damp-heat resistance, corrosion resistance and mildew resistance of the surface of the magnesium alloy in the harsh marine atmospheric environment. The method is simple in technological process, convenient to operate, capable of forming a damp-heat-resistant, corrosion-resistant and mould-corrosion-resistant coating on the surface of the magnesium alloy, environmentally friendly, remarkable in application value and capable of meeting the actual requirements for novel multifunctional magnesium alloy materials in the fields of aerospace, ocean engineering and the like.

Description

Technical Field

[0001] The present invention belongs to the field of magnesium alloy surface treatment, and in particular relates to a multifunctional coating on the surface of a magnesium alloy that is resistant to moisture, heat, corrosion and mildew, and a preparation method and application thereof. Background Art

[0002] Magnesium alloy is a lightweight, high-strength metallic material with excellent specific stiffness and strength. Its density is only two-thirds that of aluminum and one-quarter that of steel. As the lightest metallic structural material, it is hailed as "the green engineering material with the greatest development and application potential of the century." Magnesium alloy also boasts excellent thermal conductivity, electromagnetic shielding, and recyclability, offering broad application prospects in the automotive, aerospace, electronics, communications, and medical devices sectors. Furthermore, magnesium alloy offers excellent machinability and low casting costs, making it a highly sought-after lightweight material in modern industry and engineering. However, despite its significant advantages in many fields, its application remains limited by several key issues. Magnesium alloys are chemically active and susceptible to rapid oxidation and corrosion reactions in air, water, and salt spray environments. Especially in hot and humid environments, their surfaces are susceptible to corrosion products, leading to rapid performance degradation. This drawback severely restricts the application of magnesium alloys in harsh environments such as humid and marine environments. Therefore, improving the surface corrosion resistance of magnesium alloys has become a key research and engineering challenge to expand their application areas.

[0003] In many practical applications, magnesium alloys must contend with conventional corrosion and withstand the ravages of long-term, hot and humid environments. Furthermore, in marine engineering, aerospace equipment, and outdoor installations, magnesium alloys are exposed to high humidity, high temperatures, and microbial growth, making their surfaces susceptible to severe corrosion and even mold growth. This mold growth not only accelerates corrosion but can also affect product functionality and appearance, potentially leading to health and safety issues.

[0004] Therefore, the development of a multifunctional composite coating with moisture and heat resistance, corrosion resistance and mildew resistance has become the focus of current research. Summary of the Invention

[0005] In view of the defects in the above-mentioned prior art, the purpose of the present invention is to provide a multifunctional coating for the surface of magnesium alloy that is resistant to moisture, heat, corrosion and mildew in harsh marine atmospheric environment, as well as its preparation and application.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A multifunctional coating for the surface of a magnesium alloy that is resistant to heat and moisture, corrosion, and mildew, the multifunctional coating comprising an inner layer and an outer layer; wherein the inner layer is a micro-arc oxidation layer containing Ta, Sn, and Sb elements, and the outer layer is an epoxy resin organic coating containing modified conductive mica powder.

[0008] The thickness of the inner layer is 5 to 12 μm, and the thickness of the outer layer is 50 to 100 μm.

[0009] The inner layer is prepared by micro-arc oxidation, and the outer layer is prepared by spraying.

[0010] Specifically, the inner layer is a micro-arc oxidation treatment of the magnesium alloy after pre-treatment, and then dried to obtain a micro-arc oxidation coating containing Ta, Sn, and Sb elements;

[0011] The outer layer is a modified conductive mica powder-epoxy resin organic coating sprayed on the surface of the magnesium alloy after micro-arc oxidation treatment.

[0012] A method for preparing the heat-resistant, corrosion-resistant and mildew-resistant multifunctional coating on the surface of a magnesium alloy as claimed in claim 1, characterized in that it comprises the following steps:

[0013] S1: Pre-treatment of the magnesium alloy to be processed;

[0014] S2: The magnesium alloy after the pretreatment in S1 is subjected to micro-arc oxidation treatment and dried to obtain a micro-arc oxidation coating containing Ta, Sn, and Sb elements;

[0015] S3: Prepare an organic coating containing modified conductive mica powder and epoxy resin, and spray the organic coating on the surface of the magnesium alloy after micro-arc oxidation treatment;

[0016] S4: The magnesium alloy obtained in step S3 is placed in a drying oven and dried at 30° C. for 10-12 hours.

[0017] Furthermore, the pretreatment in step S1 includes polishing, degreasing, cleaning, and drying; wherein the polishing is to polish the surface of the magnesium alloy with silicon carbide sandpaper, the silicon carbide sandpaper is 800-3000#; and the degreasing is to clean and polish with acetone solution.

[0018] Furthermore, in step S2, the electrolyte used in the micro-arc oxidation treatment includes 8-12 g / L of sodium hexametaphosphate, 6-10 g / L of sodium silicate, 2-6 g / L of sodium hydroxide, 3-12 g / L of tantalum pentoxide, and 3-12 g / L of nano-antimony tin oxide.

[0019] Furthermore, in step S2, the working electrode of the micro-arc oxidation treatment is a magnesium alloy, the counter electrode is a stainless steel plate, and the treatment parameters are: voltage 280-320V, frequency 400-500Hz, and oxidation time 1-5min.

[0020] Furthermore, in step S3, the modified conductive mica powder-epoxy resin organic coating component includes modified conductive mica powder, tetrahydrofuran, epoxy resin, and polyamide; wherein the mass ratio of the modified conductive mica powder to the epoxy resin is (1-2):1, the mass ratio of the modified conductive mica powder to the tetrahydrofuran is 1:1; and the mass ratio of the epoxy resin to the polyamide is 3:1.

[0021] The modified conductive mica powder is prepared by mixing conductive mica powder and titanate coupling agent in anhydrous ethanol at 65-75 DEG C and stirring with magnetic force for 50-70 minutes.

[0022] The invention discloses an application of a heat-resistant, corrosion-resistant and mildew-resistant multifunctional coating on a magnesium alloy surface, wherein the multifunctional coating is used to improve the heat-resistant, corrosion-resistant and mildew-resistant properties of the magnesium alloy surface in a harsh marine atmospheric environment.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention can significantly improve the moisture and heat resistance and corrosion resistance of magnesium alloys by constructing micro-arc oxidation and organic composite coatings on the surface of magnesium alloys. The addition of Ta, Sn and Sb elements improves the chemical stability of the coating, improves the moisture and heat resistance and corrosion resistance of the coating, and at the same time, based on the growth inhibition effect of Sn and Sb elements on microorganisms, the coating is given the ability to resist the growth of mold, thereby promoting the application of advanced magnesium alloy materials in harsh marine atmospheric environments. At the same time, by functionally modifying the organic coating and adding modified conductive mica powder, the coating is given good anti-mildew properties. This multifunctional coating can effectively solve the application bottleneck of magnesium alloys in complex environments, enhance its application potential in fields such as marine engineering, and provide reliable guarantees for the practical application of new materials.

[0025] The process of the present invention is simple and easy to operate. It can form a coating on the surface of the magnesium alloy that is resistant to moisture and heat, corrosion and mildew erosion. It is green and environmentally friendly, has significant application value, and can meet the actual needs of aerospace, marine engineering and other fields for new multifunctional magnesium alloy materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a comparison diagram of the electrochemical polarization curves before and after preparation of the VW75 magnesium alloy coating in Example 1 of the present invention.

[0027] Figure 2 This is a comparison diagram of the three-dimensional morphology of the VW75 magnesium alloy coating before and after the moisture and heat resistance test in Example 1 of the present invention.

[0028] Figure 3 This is a comparison of the appearance of the VW75 magnesium alloy coating before and after the mildew resistance test in Example 1 of the present invention.

[0029] Figure 4This is a comparison diagram of the electrochemical polarization curves before and after preparation of the VW75 magnesium alloy coating in Example 2 of the present invention.

[0030] Figure 5 This is a comparison of the three-dimensional morphologies of the VW75 magnesium alloy coating before and after the moisture and heat resistance test in Example 2 of the present invention.

[0031] Figure 6 This is a comparison of the appearance of the VW75 magnesium alloy coating before and after the mildew resistance test in Example 2 of the present invention.

[0032] Figure 7 1 is a comparison diagram of the electrochemical polarization curves of Example 1 of the present invention and Comparative Example 1.

[0033] Figure 8 This is a comparison of the three-dimensional morphologies of Example 1 of the present invention and Comparative Example 1 after the moisture and heat resistance test.

[0034] Figure 9 This is a comparison of the appearances of Example 1 and Comparative Example 2 after the anti-mildew test. DETAILED DESCRIPTION

[0035] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, provide detailed implementation methods and specific operating procedures, and will help those skilled in the art to further understand the present invention. It should be pointed out that the scope of protection of the present invention is not limited to the following embodiments, and a number of adjustments and improvements made under the premise of the concept of the present invention all fall within the scope of protection of the present invention.

[0036] Example 1

[0037] This embodiment relates to a multifunctional coating for magnesium alloy surface that is resistant to moisture, heat, corrosion and mildew. The preparation method and properties thereof are as follows:

[0038] (1) Pretreatment of VW75 magnesium alloy

[0039] The surface of VW75 magnesium alloy was polished with 800#, 1200#, 2000#, and 3000# silicon carbide sandpaper in turn, and polished with a polishing cloth; the sample was degreased with acetone, and then ultrasonically cleaned with deionized water; finally, it was cleaned with anhydrous ethanol and dried.

[0040] (2) performing micro-arc oxidation on the polished VW75 magnesium alloy and drying it to obtain a micro-arc oxidation layer containing Ta, Sn, and Sb elements;

[0041] The specific process of micro-arc oxidation treatment is:

[0042] Electrolyte preparation: Take a certain amount of sodium hexametaphosphate, sodium silicate, and sodium hydroxide, add an appropriate amount of deionized water, and stir to fully dissolve, so that the sodium hexametaphosphate is 10g / L, the sodium silicate is 8g / L, and the sodium hydroxide is 4g / L. Then, tantalum pentoxide and nano-antimony tin oxide particles are added to the solution to make the concentrations of 6g / L and 3g / L, respectively, to prepare the electrolyte;

[0043] Using a stainless steel plate as the cathode, the pretreated VW75 magnesium alloy material was installed on the anode and immersed in the prepared electrolyte. The treatment parameters were voltage 300V, frequency 500Hz, and oxidation time 120s; it was rinsed with anhydrous ethanol and dried.

[0044] (3) preparing an organic coating containing modified conductive mica powder and epoxy resin, and spraying the organic coating on the surface of the magnesium alloy after micro-arc oxidation treatment;

[0045] The specific organic coating preparation process is as follows:

[0046] First, the conductive mica powder was modified. The conductive mica powder and titanate coupling agent were mixed in anhydrous ethanol and magnetically stirred for 1 h at a stirring temperature of 70°C.

[0047] Then, an organic coating is prepared, which includes modified conductive mica powder, tetrahydrofuran, epoxy resin, and polyamide, wherein the mass ratio of modified conductive mica powder: epoxy resin is 1.5:1; the mass ratio of modified conductive mica powder: tetrahydrofuran is 1:1; and the mass ratio of epoxy resin: polyamide is 3:1.

[0048] Afterwards, the organic coating is sprayed onto the surface of the magnesium alloy after the micro-arc oxidation treatment using a spray gun.

[0049] (4) Drying the sprayed magnesium alloy to obtain a multifunctional coating having heat and moisture resistance, corrosion resistance, and mildew resistance on the surface of the magnesium alloy, wherein the drying temperature is 30° C. and the drying time is 10 hours.

[0050] Coating performance test

[0051] 1. Coating thickness

[0052] The coating cross-section thickness was measured using SEM, where the inner layer thickness was 5.43 μm and the outer layer thickness was 54.27 μm.

[0053] 2. Electrochemical performance test

[0054] The corrosion resistance of the magnesium alloy samples prepared above and the untreated magnesium alloy in natural seawater was evaluated using an electrochemical workstation. The magnesium alloy was installed in a customized electrochemical cell as the working electrode, an Ag / AgCl (saturated KCl) electrode was used as the reference electrode, and a platinum mesh (20 mm × 20 mm × 0.1 mm) was used as the counter electrode. Figure 1 It can be seen that the corrosion resistance of the magnesium alloy surface is greatly improved after coating preparation, the electrochemical corrosion potential moves significantly in the positive direction, and the self-corrosion current density is reduced.

[0055] 3. Moisture and heat resistance test

[0056] The magnesium alloy samples prepared above and the untreated magnesium alloy were placed in a drying oven and heated at 120°C for 3600s. The heated samples were then immersed in natural seawater for 3600s. After the immersion was completed, the immersed samples were washed in anhydrous ethanol, the surface natural seawater was removed and the samples were placed in a drying oven again and heated at 120°C for 3600s. The above process was repeated 4 times for all samples. The three-dimensional morphology of the samples was then observed using a laser confocal microscope. Figure 2 It can be seen that after the wet heat test, there is no obvious change on the surface of the magnesium alloy after coating preparation.

[0057] 4. Anti-mildew performance test

[0058] According to GB / T 1741-2020, the fungus resistance test of VW75 magnesium alloy before and after coating was carried out. Figure 3 It can be seen that no obvious corrosion occurs to the magnesium alloy after coating preparation.

[0059] Example 2

[0060] This embodiment relates to a multifunctional coating for magnesium alloy surface that is resistant to moisture, heat, corrosion and mildew. The preparation method and properties thereof are as follows:

[0061] The preparation of the micro-arc oxidation layer containing Ta, Sn, and Sb elements in the inner layer is the same as that in Example 1, except that the amount of the components containing the modified conductive mica powder-epoxy resin organic coating is different, specifically:

[0062] Equipped with modified conductive mica powder-epoxy resin organic coating, the organic coating is sprayed on the surface of the magnesium alloy after micro-arc oxidation treatment;

[0063] The specific organic coating preparation process is as follows:

[0064] First, the conductive mica powder was modified. The conductive mica powder and titanate coupling agent were mixed in anhydrous ethanol and magnetically stirred for 1 h at a stirring temperature of 70°C.

[0065] Then, an organic coating is prepared, which includes modified conductive mica powder, tetrahydrofuran, epoxy resin, and polyamide, wherein the mass ratio of modified conductive mica powder: epoxy resin is 2:1; the mass ratio of modified conductive mica powder: tetrahydrofuran is 1:1; and the mass ratio of epoxy resin: polyamide is 3:1.

[0066] Afterwards, the organic coating is sprayed onto the surface of the magnesium alloy after the micro-arc oxidation treatment using a spray gun.

[0067] The sprayed magnesium alloy is dried to obtain a multifunctional coating having heat and moisture resistance, corrosion resistance, and mildew resistance on the surface of the magnesium alloy, wherein the drying temperature is 30° C. and the drying time is 10 hours.

[0068] Coating performance test

[0069] 1. Coating thickness

[0070] The thickness of the coating cross section was measured using SEM. The thickness of the inner layer was 5.43 μm, and the thickness of the outer layer was 84.40 μm.

[0071] 2. Electrochemical performance test

[0072] The corrosion resistance of the magnesium alloy samples prepared above and the untreated magnesium alloy in natural seawater was evaluated using an electrochemical workstation. The magnesium alloy was installed in a customized electrochemical cell as the working electrode, an Ag / AgCl (saturated KCl) electrode was used as the reference electrode, and a platinum mesh (20 mm × 20 mm × 0.1 mm) was used as the counter electrode. Figure 4 It can be seen that the corrosion resistance of the magnesium alloy surface is greatly improved after coating preparation, the electrochemical corrosion potential moves significantly in the positive direction, and the self-corrosion current density is reduced.

[0073] 3. Moisture and heat resistance test

[0074] The magnesium alloy samples prepared above and the untreated magnesium alloy were placed in a drying oven and heated at 120°C for 3600s. The heated samples were then immersed in natural seawater for 3600s. After the immersion was completed, the immersed samples were washed in anhydrous ethanol, the surface natural seawater was removed and the samples were placed in a drying oven again and heated at 120°C for 3600s. The above process was repeated 4 times for all samples. The three-dimensional morphology of the samples was then observed using a laser confocal microscope. Figure 5 It can be seen that after the wet heat test, the surface of the magnesium alloy prepared with the coating has no obvious changes.

[0075] 4. Anti-mildew performance test

[0076] According to GB / T 1741-2020, the fungus resistance test of VW75 magnesium alloy before and after coating was carried out. Figure 6It can be seen that no obvious corrosion occurs to the magnesium alloy after micro-arc oxidation treatment.

[0077] Comparative Example 1

[0078] The difference between Comparative Example 1 and Example 1 is that the VW75 magnesium alloy material is only coated with a micro-arc oxidation coating.

[0079] The specific process of micro-arc oxidation treatment is:

[0080] Preparation of electrolyte: Take a certain amount of sodium hexametaphosphate, sodium silicate, and sodium hydroxide, add an appropriate amount of deionized water, and stir to fully dissolve, so that the concentration of sodium hexametaphosphate is 10g / L, the concentration of sodium silicate is 8g / L, and the concentration of sodium hydroxide is 4g / L to obtain the electrolyte;

[0081] Using a stainless steel plate as the cathode, the pretreated VW75 magnesium alloy material was installed on the anode and immersed in the prepared electrolyte. The treatment parameters were voltage 300V, frequency 500Hz, and oxidation time 120s; it was rinsed with anhydrous ethanol and dried.

[0082] Coating performance test

[0083] 1. Electrochemical performance test

[0084] The corrosion resistance of the prepared samples in natural seawater was evaluated using an electrochemical workstation. The prepared samples were installed in a custom electrochemical cell as working electrodes, using Ag / AgCl (saturated KCl) electrodes as reference electrodes and platinum mesh (20 mm × 20 mm × 0.1 mm) as counter electrodes. Figure 7 It can be seen that compared with Example 1, the electrochemical corrosion potential of Comparative Example 1 is lower and the self-corrosion current density is greater.

[0085] 2. Moisture and heat resistance test

[0086] The samples prepared above were placed in a drying oven and heated at 120°C for 3600s. The heated samples were then immersed in natural seawater for 3600s. After immersion, the immersed samples were washed in anhydrous ethanol, the surface natural seawater was removed, and the samples were placed in a drying oven again and heated at 120°C for 3600s. The above process was repeated 4 times for all samples. The three-dimensional morphology of the samples was then observed using a laser confocal microscope. Figure 8 As can be seen in the figure, after the damp heat test, the surface of the sample in Comparative Example 1 changed significantly compared to Example 1. This shows that the coating in Comparative Example 1 does not contain Ta, Sn, and Sb elements, resulting in a larger porosity and lower chemical stability of the coating, which reduces the damp heat resistance and corrosion resistance of the magnesium alloy.

[0087] Comparative Example 2

[0088] The difference between Comparative Example 2 and Example 1 is that the composite coating does not contain modified conductive mica powder.

[0089] The preparation of the micro-arc oxidation layer containing Ta, Sn and Sb elements in the inner layer is the same as that in Example 1.

[0090] Equipped with epoxy resin organic coating, the organic coating is sprayed on the surface of the magnesium alloy after micro-arc oxidation treatment;

[0091] The specific organic coating preparation process is as follows:

[0092] The organic coating comprises tetrahydrofuran, epoxy resin and polyamide, wherein the mass ratio of epoxy resin to tetrahydrofuran is 1:1; the mass ratio of epoxy resin to polyamide is 3:1.

[0093] Afterwards, the coating is sprayed onto the surface of the micro-arc oxidation layer using a spray gun.

[0094] The sprayed magnesium alloy is dried to obtain a composite coating on the surface of the magnesium alloy, wherein the drying temperature is 30° C. and the drying time is 10 hours.

[0095] Anti-mildew performance test

[0096] The samples were tested for mold resistance according to GB / T 1741-2020. Figure 9 It can be seen that compared with Example 1, the surface of the sample in Comparative Example 2 was corroded.

[0097] It can be seen that the coating of Comparative Example 2 does not contain modified conductive mica powder and thus cannot inhibit the adhesion of mold, resulting in a decrease in the anti-mold performance of the magnesium alloy.

[0098] In summary, the present invention produces a multifunctional magnesium alloy coating with a dense and uniform microstructure on the surface of the magnesium alloy, which has good moisture and heat resistance and corrosion resistance. The addition of Ta, Sn and Sb elements improves the chemical stability of the coating, improves the moisture and heat resistance and corrosion resistance of the coating, and at the same time, based on the growth inhibition effect of Sn and Sb elements on microorganisms, the coating is given the ability to resist the growth of mold, thereby promoting the application of advanced magnesium alloy materials in harsh marine atmospheric environments. At the same time, by functionally modifying the organic coating and adding modified conductive mica powder, the coating is given good mildew resistance. This multifunctional coating can effectively solve the application bottleneck of magnesium alloys in complex environments, enhance its application potential in fields such as marine engineering, and provide reliable guarantees for the practical application of new materials.

[0099] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A multifunctional coating for magnesium alloy surface that is resistant to heat, moisture, corrosion and mildew, characterized in that: The multifunctional coating comprises an inner layer and an outer layer; wherein the inner layer is a micro-arc oxidation layer containing Ta, Sn, and Sb elements, and the outer layer is an epoxy resin organic coating containing modified conductive mica powder.

2. The multifunctional coating for magnesium alloy surface resistant to heat and moisture, corrosion and mildew according to claim 1, characterized in that: The thickness of the inner layer is 5 to 12 μm, and the thickness of the outer layer is 50 to 100 μm.

3. The multifunctional coating for magnesium alloy surface resistant to heat and moisture, corrosion and mildew according to claim 1, characterized in that: The inner layer is a micro-arc oxidation coating containing Ta, Sn and Sb elements obtained by micro-arc oxidation treatment of the magnesium alloy after pre-treatment and drying; The outer layer is a modified conductive mica powder-epoxy resin organic coating sprayed on the surface of the magnesium alloy after micro-arc oxidation treatment.

4. A method for preparing a heat-resistant, corrosion-resistant and mildew-resistant multifunctional coating on a magnesium alloy surface according to any one of claims 1 to 3, characterized in that: The steps include: S1: Pre-treatment of the magnesium alloy to be processed; S2: The magnesium alloy after the pretreatment in S1 is subjected to micro-arc oxidation treatment and dried to obtain a micro-arc oxidation coating containing Ta, Sn, and Sb elements; S3: Prepare an organic coating containing modified conductive mica powder and epoxy resin, and spray the organic coating on the surface of the magnesium alloy after micro-arc oxidation treatment; S4: The magnesium alloy obtained in step S3 is placed in a drying oven and dried at 30° C. for 10-12 hours.

5. The method for preparing the heat-resistant, corrosion-resistant and mildew-resistant multifunctional coating on the surface of a magnesium alloy according to claim 4, characterized in that: The pre-treatment in step S1 includes polishing, degreasing, cleaning, and drying; The polishing process is to polish the surface of the magnesium alloy with silicon carbide sandpaper, wherein the silicon carbide sandpaper is 800-3000#; and the degreasing process is to clean and polish with acetone solution.

6. The method for preparing the heat-resistant, corrosion-resistant and mildew-resistant multifunctional coating on the surface of a magnesium alloy according to claim 4, characterized in that: In step S2, the electrolyte used in the micro-arc oxidation treatment includes 8-12 g / L of sodium hexametaphosphate, 6-10 g / L of sodium silicate, 2-6 g / L of sodium hydroxide, 3-12 g / L of tantalum pentoxide, and 3-12 g / L of nano-antimony tin oxide.

7. The method for preparing the heat-resistant, corrosion-resistant and mildew-resistant multifunctional coating on the surface of a magnesium alloy according to claim 4, characterized in that: In step S2, the working electrode of the micro-arc oxidation treatment is a magnesium alloy, the counter electrode is a stainless steel plate, and the treatment parameters are: voltage 280-320V, frequency 400-500Hz, and oxidation time 1-5min.

8. The method for preparing the heat-resistant, corrosion-resistant and mildew-resistant multifunctional coating on the surface of a magnesium alloy according to claim 4, characterized in that: In step S3, the modified conductive mica powder-epoxy resin organic coating component includes modified conductive mica powder, tetrahydrofuran, epoxy resin, and polyamide; wherein the mass ratio of the modified conductive mica powder to the epoxy resin is (1-2):1, the mass ratio of the modified conductive mica powder to the tetrahydrofuran is 1:1; and the mass ratio of the epoxy resin to the polyamide is 3:

1.

9. The method for preparing the heat-resistant, corrosion-resistant and mildew-resistant multifunctional coating on the surface of a magnesium alloy according to claim 8, characterized in that: The modified conductive mica powder is prepared by mixing conductive mica powder and titanate coupling agent in anhydrous ethanol at 65-75 DEG C and stirring with magnetic force for 50-70 minutes.

10. Application of a multifunctional coating for magnesium alloy surface that is resistant to moisture, heat, corrosion and mildew, characterized in that: The multifunctional coating is used to improve the moisture and heat resistance, corrosion resistance and mildew resistance of the magnesium alloy surface in a harsh marine atmospheric environment.

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