Magnesium alloy corrosion-resistant coating and use method thereof

Abstract

The invention relates to a magnesium alloy corrosion-resistant coating and a use method thereof, and belongs to the technical field of magnesium alloy treatment. According to the preparation method, micro-arc oxidation treatment and electrophoresis technologies are combined, and a novel magnesium alloy corrosion-resistant coating preparation technology is formed. According to the technology, the corrosion resistance of the coating is improved, the adhesive force and the attractiveness of the coating are enhanced, and a coating formula with good corrosion resistance and attractiveness is prepared according to the proportion of the emulsion, the color paste and the coating; according to the method, micro-arc oxidation is adjusted, so that the film thickness of the magnesium alloy is controlled within the range of 8-15 microns, and the magnesium alloy is combined with KNT831 cathode electrophoretic paint and corrosion-resistant paint, so that the treated magnesium alloy has better corrosion resistance; and meanwhile, the film layer is controlled within the range of 8-15 microns during micro-arc oxidation of the magnesium alloy, so that the production time of the magnesium alloy is obviously shortened, the energy consumption in the micro-arc oxidation process is further reduced, and the production efficiency is improved at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of magnesium alloy processing and relates to a magnesium alloy corrosion-resistant coating and a use method thereof. Background Art

[0002] With the rapid development of the low-altitude economy, the weight of aircraft such as unmanned equipment and flying cars seriously affects their hovering time. Therefore, the research and development of lightweight materials has become an important task in the industry. Magnesium alloys stand out from many metals due to their low density, excellent specific strength and specific stiffness. Although researchers have improved the composition and process, magnesium alloys still have high chemical activity and are very prone to corrosion in the atmospheric environment, which greatly limits the use scenarios of magnesium alloys. It is currently believed that preparing an anti-corrosion coating on the surface of magnesium alloys to improve the corrosion resistance of the material has become a practical method. For products in general use environments, such as mobile phone middle frames, micro-arc oxidation technology is conventionally used to prepare a corrosion-resistant coating mainly composed of oxides on the surface of magnesium alloys by electrochemical methods. Its neutral salt spray resistance is in the range of 100-150 hours. However, for some products with higher corrosion resistance requirements, micro-arc oxidation cannot meet their needs. Electrophoretic coating technology is widely used in automotive primers due to its excellent corrosion resistance and ease of processing. However, when electrophoretic coating is applied directly to magnesium alloys, the bonding between the electrophoretic layer and the alloy is poor, causing it to easily peel off and failing to achieve the desired corrosion protection. Therefore, a patent has been developed to combine the two, creating a micro-arc oxidation (MAO) coating. This coating forms an in-situ coating on the surface of a magnesium alloy, and its excellent bonding strength to the magnesium alloy. Researchers have combined the two to create a MAO-ELC composite coating, leveraging their synergistic effect to improve the coating's corrosion resistance.

[0003] In the current patents, for the micro-arc oxidation-electrophoretic composite coating, the thickness of the micro-arc oxidation film in the Chinese patent publication number CN 118497863A is about 25 to 30 μm, and its corrosion resistance is about 3000 hours, which is the micro-arc oxidation-electrophoretic composite coating with the highest neutral salt spray resistance seen so far. Summary of the Invention

[0004] The purpose of the present invention is to provide a magnesium alloy corrosion-resistant coating and a method of using the same, which has the characteristics of good corrosion resistance.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A magnesium alloy corrosion-resistant coating, the coating formula is as follows: by mass percentage, 30-40% epoxy resin, 15-20% phenolic resin, 5-10% modified inorganic filler, 15-18% butanol, 10-15% toluene, 5-7% monoethanolamine, 2-3% dispersant,

[0007] The preparation method of the modified inorganic filler is as follows:

[0008] S1.1: Titanium dioxide and zirconium nitrate were mixed in a mass ratio of 2:1 and ground in a ball mill at 400 rpm for 1 h. The resulting mixture was transferred to 600°C and calcined for 3 h. After calcination, the mixture was cooled to room temperature and pulverized to obtain Mixture A.

[0009] S1.2: Sodium silicate is dissolved in deionized water to obtain a sodium silicate solution having a mass fraction of 30-40%. Mixture A is immersed in the sodium silicate solution and ultrasonicated at 40°C for 1-2 hours, wherein the mass ratio of mixture A to sodium silicate is 1:(1-2). After the ultrasonication is completed, the mixture is filtered and dried to obtain mixture B.

[0010] S1.3: Dissolve graphene oxide in deionized water to obtain a graphene oxide solution with a mass fraction of 40-50%. Immerse mixture B in the graphene oxide solution and sonicate at room temperature for 1 hour. The mass ratio of mixture B to graphene oxide is 1:1. After the sonication is completed, filter and collect the filter cake.

[0011] S1.4: Freezing the filter cake in liquid nitrogen for 15 to 20 minutes, and then drying it at -50°C under vacuum for 6 hours. After drying, crushing and grinding the filter cake to obtain the modified inorganic filler.

[0012] The coating preparation method is as follows:

[0013] Put epoxy resin, phenolic resin, butanol, toluene and monoethanolamine into a reaction kettle, stir at a speed of 200 r / min, heat to 70°C while stirring, add modified inorganic filler and dispersant after complete dissolution, increase the speed to 250 r / min, stir for 4 to 6 hours, and obtain the coating;

[0014] The magnesium alloy corrosion-resistant coating is coated on the surface of the micro-arc oxidation coating, and the film thickness of the micro-arc oxidation coating is 8 to 15 μm.

[0015] Furthermore, the dispersant is polyethylene glycol, and the number average molecular weight ranges from 2000 to 4000.

[0016] Furthermore, the mixture A obtained by grinding in S1.1 has a particle size of 500 mesh.

[0017] Furthermore, the particle size of the modified inorganic filler obtained by grinding in S1.4 is 800 mesh.

[0018] A method for using a magnesium alloy corrosion-resistant coating, wherein the specific steps of the method are as follows:

[0019] S5.1: Sodium phosphate, sodium fluoride, and sodium hydroxide are mixed to form an electrolyte. The cleaned and dried magnesium alloy is placed in an electrolytic cell and subjected to micro-arc oxidation treatment using the magnesium alloy as an anode and a stainless steel plate as a cathode to obtain a magnesium alloy substrate I after micro-arc oxidation treatment.

[0020] S5.2: Mix cathodic electrophoretic paint KNT831 and corrosion-resistant coating in a mass ratio of 1:1 to obtain a mixture D. Curing the mixture D at 30°C for 24 h, the mixture is then attached to the surface of a magnesium alloy substrate I by electrophoresis treatment to obtain a magnesium alloy substrate II.

[0021] S5.3: After the electrophoresis treatment is completed, the obtained magnesium alloy substrate II is cleaned with pure water. After cleaning, it is baked and solidified.

[0022] Furthermore, the electrolyte prepared in S5.1 has a sodium phosphate concentration of 10-15 g / L, a sodium fluoride concentration of 4-8 g / L, a sodium hydroxide concentration of 3-6 g / L, and the solvent is deionized water.

[0023] Furthermore, the pH of the electrolyte prepared in S5.1 is 12.9-13.1.

[0024] Furthermore, the parameters of the micro-arc oxidation treatment in S5.1 are constant current control mode, and the current density is 1.5 to 2.5 A / dm 2 The frequency range is 1000-1500 Hz, the duty cycle is 25-35%, the time is 5-12 minutes, the thickness of the micro-arc oxidation coating is 8-15 μm, and the electrolyte temperature is 25-35°C.

[0025] Furthermore, the parameters of the electrophoresis treatment in S5.2 are as follows: constant voltage mode is adopted, the magnesium alloy substrate is the cathode, the stainless steel plate is the anode, the electrophoresis tank temperature is 30±0.5°C, the voltage is controlled to increase to 220V within 15s, and the duration is 5min.

[0026] Furthermore, the baking and curing parameters in S5.3 are a baking temperature of 175° C. and a baking time of 0.5 h.

[0027] The epoxy resin in the present invention was purchased from Shenyang Elex Chemical Co., Ltd. with a CAS number of 24969-06-0 and a purity of 99%; the phenolic resin in the present invention was purchased from Shenyang Elex Chemical Co., Ltd. with a CAS number of 9003-35-4 and a purity of 99%; the titanium dioxide in the present invention was purchased from Tianjin Linyi Chemical Technology Co., Ltd. with a purity of 99%; the sodium silicate in the present invention was purchased from Jiangsu Leien Environmental Protection Technology Co., Ltd. with a purity of 99%; and the cathode electrophoretic paint KNT831 in the present invention was purchased from Shanghai Jinlitai Chemical Co., Ltd.

[0028] The present invention provides a magnesium alloy corrosion-resistant coating and a method for using the same. The coating formula and preparation process, as well as the pretreatment and electrophoretic treatment process of the magnesium alloy substrate, significantly improve the corrosion resistance of the magnesium alloy. The epoxy resin and phenolic resin in the coating provide a tough coating foundation, while the modified inorganic filler effectively enhances the density and adhesion of the coating through its special preparation process, further improving the corrosion resistance of the coating. At the same time, the optimization of the electrolyte formula and micro-arc oxidation treatment parameters enables the formation of a uniform and dense micro-arc oxidation coating on the surface of the magnesium alloy substrate, further enhancing the protective effect of the coating. The electrophoretic treatment ensures that the coating can be evenly and tightly adhered to the surface of the magnesium alloy substrate, avoiding problems such as coating shedding or cracking. After baking and curing, a strong bond is formed between the coating and the magnesium alloy substrate, further improving the overall corrosion resistance.

[0029] By adding epoxy resin and phenolic resin, modified inorganic fillers and other additives, the coating can form a tough and dense protective film on the surface of the magnesium alloy, effectively isolating the corrosive medium, thereby significantly improving the corrosion resistance of the magnesium alloy. The resin and modified inorganic filler in the coating can enhance the adhesion and mechanical strength of the coating, making the coating less likely to fall off or be damaged when subjected to external forces.

[0030] The components in the modified inorganic filler, such as titanium dioxide, zirconium nitrate, sodium silicate and graphene oxide, can work synergistically to enhance the corrosion resistance and mechanical properties of the coating. The modified inorganic filler has good dispersibility and stability, can be evenly dispersed in the coating, and improve the overall performance of the coating.

[0031] After titanium dioxide and zirconium nitrate are ground in a ball mill, a tight composite structure is formed through chemical bonds and physical adsorption. This structure is further solidified during the roasting process to form a compound with excellent corrosion resistance. The surface of the composite structure is rich in active sites. The composite structure of titanium dioxide and zirconium nitrate is immersed in a sodium silicate solution and subjected to ultrasonic treatment. The silicate ions react chemically with the active sites on the surface of the structure to form silicon-oxygen bonds (Si-O). This not only enhances the bonding force between the filler and the resin matrix, but also improves the corrosion resistance and dispersibility of the filler. Graphene oxide is then used for modification to further enhance the mechanical strength and corrosion resistance of the coating.

[0032] Epoxy resin and phenolic resin, the primary film-forming components of the coating, form a tough, dense protective film that shields the magnesium alloy from corrosive media. They also possess excellent adhesion and mechanical properties, enhancing the overall performance of the coating. By combining titanium dioxide, zirconium nitrate, sodium silicate, and graphene oxide, a modified inorganic filler with superior performance is formed. This significantly enhances the coating's corrosion resistance and mechanical properties, while also improving its dispersibility and stability. Butanol and toluene, as solvents, dissolve the resin and other additives, resulting in a uniform liquid coating for easier application and coating. They also adjust the coating's viscosity and fluidity, ensuring uniform and smooth adhesion to the magnesium alloy surface. Monoethanolamine, as an additive, adjusts the coating's pH, improving its stability and dispersibility. Furthermore, it reacts chemically with the resin and other components, forming stronger chemical bonds and enhancing the coating's adhesion and mechanical properties.

[0033] Beneficial effects of the present invention:

[0034] This invention combines micro-arc oxidation (MAO) with electrophoresis technology to create a novel corrosion-resistant coating preparation technology for magnesium alloys. This technology not only improves the coating's corrosion resistance, but also enhances its adhesion and aesthetics. By adjusting the ratio of emulsion, colorant, and coating, a coating formula with excellent corrosion resistance and aesthetics is formulated. The invention achieves improved corrosion resistance for magnesium alloys by adjusting the MAO film thickness to within a range of 8 to 15 μm. This, combined with KNT831 cathodic electrophoretic paint and corrosion-resistant coatings, results in a significantly shorter production time because the MAO film thickness is controlled within a range of 8 to 15 μm. This significantly reduces energy consumption during the MAO process and increases production efficiency. DETAILED DESCRIPTION

[0035] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0036] Example 1

[0037] A magnesium alloy corrosion-resistant coating, the coating formula is as follows, by mass percentage, epoxy resin 40%, phenolic resin 17%, modified inorganic filler 10%, butanol 15%, toluene 10%, monoethanolamine 5%, polyethylene glycol 20003%,

[0038] The preparation method of the modified inorganic filler is as follows:

[0039] S1.1: Titanium dioxide and zirconium nitrate were mixed in a mass ratio of 2:1 and ground in a ball mill at 400 rpm for 1 h. The resulting mixture was transferred to 600°C and calcined for 3 h. After calcination, the mixture was cooled to room temperature and pulverized to obtain a mixture A having a particle size of 500 mesh.

[0040] S1.2: Sodium silicate was dissolved in deionized water to obtain a 35% sodium silicate solution. Mixture A was immersed in the sodium silicate solution and ultrasonicated at 40°C for 2 h. The mass ratio of mixture A to sodium silicate was 1:1. After the ultrasonication, the mixture was filtered and dried to obtain mixture B.

[0041] S1.3: Dissolve graphene oxide in deionized water to obtain a 45% by mass graphene oxide solution. Immerse mixture B in the graphene oxide solution and sonicate at room temperature for 1 h. The mass ratio of mixture B to graphene oxide is 1:1. After sonication, filter and collect the filter cake.

[0042] S1.4: The filter cake was placed in liquid nitrogen for freezing for 15 minutes, and then dried at -50°C under vacuum for 6 hours. After drying, the filter cake was crushed and ground to obtain the modified inorganic filler, wherein the particle size of the modified inorganic filler was 800 mesh;

[0043] The coating preparation method is as follows:

[0044] Epoxy resin, phenolic resin, butanol, toluene, and monoethanolamine are placed in a reaction kettle and stirred at a speed of 200 r / min. The temperature is raised to 70° C. while stirring. After complete dissolution, modified inorganic fillers and dispersants are added, the speed is increased to 250 r / min, and stirring is carried out for 6 hours to obtain the coating.

[0045] A method for using a magnesium alloy corrosion-resistant coating, wherein the specific steps of the method are as follows:

[0046] S5.1: Sodium phosphate, sodium fluoride, and sodium hydroxide are mixed to form an electrolyte. The concentration of sodium phosphate in the electrolyte is 10 g / L, the concentration of sodium fluoride is 8 g / L, and the concentration of sodium hydroxide is 6 g / L. The solvent is deionized water. The pH of the electrolyte is 12.9-13.1. The magnesium alloy after surface cleaning and drying is placed in an electrolytic cell. Micro-arc oxidation treatment is performed with the magnesium alloy as the anode and the stainless steel plate as the cathode. The parameters of the micro-arc oxidation treatment are constant current control mode and the current density is 2 A / dm 2 The frequency range is 1500 Hz, the duty cycle is 30%, and the time is 7 min. The thickness of the micro-arc oxidation coating is 8 μm, and the electrolyte temperature is 30°C. The magnesium alloy substrate I after micro-arc oxidation treatment is obtained;

[0047] S5.2: Mix cathodic electrophoretic paint KNT831 and corrosion-resistant coating in a mass ratio of 1:1 to obtain a mixture D. After aging the mixture D at 30°C for 24 h, adhere the mixture to the surface of magnesium alloy substrate I via electrophoresis. The electrophoresis treatment is performed in a constant voltage mode, with the magnesium alloy substrate as the cathode and the stainless steel plate as the anode. The electrophoresis tank temperature is 30 ± 0.5°C, and the voltage is increased to 220 V within 15 s for 5 min to obtain magnesium alloy substrate II.

[0048] S5.3: After the electrophoresis treatment is completed, the obtained magnesium alloy substrate II is cleaned with pure water. After the cleaning is completed, it is baked and solidified. The baking and solidification parameters are a baking temperature of 175° C. and a baking time of 0.5 h.

[0049] Example 2

[0050] A magnesium alloy corrosion-resistant coating, the coating formula is as follows, by mass percentage, epoxy resin 30%, phenolic resin 20%, modified inorganic filler 10%, butanol 18%, toluene 15%, monoethanolamine 5%, polyethylene glycol 20002%,

[0051] The preparation method of the modified inorganic filler is as follows:

[0052] S1.1: Titanium dioxide and zirconium nitrate were mixed in a mass ratio of 2:1 and ground in a ball mill at 400 rpm for 1 h. The resulting mixture was transferred to 600°C and calcined for 3 h. After calcination, the mixture was cooled to room temperature and pulverized to obtain a mixture A having a particle size of 500 mesh.

[0053] S1.2: Sodium silicate was dissolved in deionized water to obtain a 30% sodium silicate solution. Mixture A was immersed in the sodium silicate solution and ultrasonicated at 40°C for 1 h. The mass ratio of mixture A to sodium silicate was 1:1. After the ultrasonication, the mixture was filtered and dried to obtain mixture B.

[0054] S1.3: Dissolve graphene oxide in deionized water to obtain a 40% by mass graphene oxide solution. Immerse mixture B in the graphene oxide solution and sonicate at room temperature for 1 h. The mass ratio of mixture B to graphene oxide is 1:1. After sonication, filter and collect the filter cake.

[0055] S1.4: The filter cake was placed in liquid nitrogen for freezing for 15 minutes, and then dried at -50°C under vacuum for 6 hours. After drying, the filter cake was crushed and ground to obtain the modified inorganic filler, wherein the particle size of the modified inorganic filler was 800 mesh;

[0056] The coating preparation method is as follows:

[0057] Epoxy resin, phenolic resin, butanol, toluene, and monoethanolamine are placed in a reaction kettle and stirred at a speed of 200 r / min. The temperature is raised to 70° C. while stirring. After complete dissolution, modified inorganic fillers and dispersants are added, the speed is increased to 250 r / min, and stirring is carried out for 4 hours to obtain the coating.

[0058] A method for using a magnesium alloy corrosion-resistant coating, wherein the specific steps of the method are as follows:

[0059] S5.1: Sodium phosphate, sodium fluoride, and sodium hydroxide are mixed to form an electrolyte. The concentration of sodium phosphate in the electrolyte is 10 g / L, the concentration of sodium fluoride is 4 g / L, and the concentration of sodium hydroxide is 3 g / L. The solvent is deionized water. The pH of the electrolyte is 12.9-13.1. The magnesium alloy after surface cleaning and drying is placed in an electrolytic cell. Micro-arc oxidation treatment is performed with the magnesium alloy as the anode and the stainless steel plate as the cathode. The parameters of the micro-arc oxidation treatment are constant current control mode and the current density is 1.5 A / dm 2 The frequency range is 1000 Hz, the duty cycle is 25%, and the time is 12 min. The thickness of the micro-arc oxidation coating is 8 μm, and the electrolyte temperature is 25°C. The magnesium alloy substrate I after micro-arc oxidation treatment is obtained;

[0060] S5.2: Mix cathodic electrophoretic paint KNT831 and corrosion-resistant coating in a mass ratio of 1:1 to obtain a mixture D. After aging the mixture D at 30°C for 24 h, adhere the mixture to the surface of magnesium alloy substrate I via electrophoresis. The electrophoresis treatment is performed in a constant voltage mode, with the magnesium alloy substrate as the cathode and the stainless steel plate as the anode. The electrophoresis tank temperature is 30 ± 0.5°C, and the voltage is increased to 220 V within 15 s for 5 min to obtain magnesium alloy substrate II.

[0061] S5.3: After the electrophoresis treatment is completed, the obtained magnesium alloy substrate II is cleaned with pure water. After the cleaning is completed, it is baked and solidified. The baking and solidification parameters are a baking temperature of 175° C. and a baking time of 0.5 h.

[0062] Example 3

[0063] A magnesium alloy corrosion-resistant coating, the coating formula is as follows, by mass percentage, epoxy resin 40%, phenolic resin 15%, modified inorganic filler 5%, butanol 15%, toluene 15%, monoethanolamine 7%, polyethylene glycol 20003%,

[0064] The preparation method of the modified inorganic filler is as follows:

[0065] S1.1: Titanium dioxide and zirconium nitrate were mixed in a mass ratio of 2:1 and ground in a ball mill at 400 rpm for 1 h. The resulting mixture was transferred to 600°C and calcined for 3 h. After calcination, the mixture was cooled to room temperature and pulverized to obtain a mixture A having a particle size of 500 mesh.

[0066] S1.2: Sodium silicate was dissolved in deionized water to obtain a 40% sodium silicate solution. Mixture A was immersed in the sodium silicate solution and ultrasonicated at 40°C for 2 h. The mass ratio of mixture A to sodium silicate was 1:2. After the ultrasonication, the mixture was filtered and dried to obtain mixture B.

[0067] S1.3: Dissolve graphene oxide in deionized water to obtain a 50% by mass graphene oxide solution. Immerse mixture B in the graphene oxide solution and sonicate at room temperature for 1 h. The mass ratio of mixture B to graphene oxide is 1:1. After sonication, filter and collect the filter cake.

[0068] S1.4: The filter cake is placed in liquid nitrogen for freezing for 20 minutes, and then dried at -50°C under vacuum for 6 hours. After drying, the filter cake is crushed and ground to obtain the modified inorganic filler, wherein the particle size of the modified inorganic filler is 800 mesh;

[0069] The coating preparation method is as follows:

[0070] Epoxy resin, phenolic resin, butanol, toluene, and monoethanolamine are placed in a reaction kettle and stirred at a speed of 200 r / min. The temperature is raised to 70° C. while stirring. After complete dissolution, modified inorganic fillers and dispersants are added, the speed is increased to 250 r / min, and stirring is carried out for 6 hours to obtain the coating.

[0071] A method for using a magnesium alloy corrosion-resistant coating, wherein the specific steps of the method are as follows:

[0072] S5.1: Sodium phosphate, sodium fluoride, and sodium hydroxide are mixed to form an electrolyte. The concentration of sodium phosphate in the electrolyte is 15 g / L, the concentration of sodium fluoride is 8 g / L, and the concentration of sodium hydroxide is 6 g / L. The solvent is deionized water. The pH of the electrolyte is 12.9-13.1. The magnesium alloy after surface cleaning and drying is placed in an electrolytic cell. Micro-arc oxidation treatment is performed with the magnesium alloy as the anode and the stainless steel plate as the cathode. The parameters of the micro-arc oxidation treatment are constant current control mode and the current density is 2.5 A / dm 2 The frequency range is 1500 Hz, the duty cycle is 35%, and the time is 5 min. The thickness of the micro-arc oxidation coating is 15 μm, and the electrolyte temperature is 35°C. The magnesium alloy substrate I after micro-arc oxidation treatment is obtained;

[0073] S5.2: Mix cathodic electrophoretic paint KNT831 and corrosion-resistant coating in a mass ratio of 1:1 to obtain a mixture D. After aging the mixture D at 30°C for 24 h, adhere the mixture to the surface of magnesium alloy substrate I via electrophoresis. The electrophoresis treatment is performed in a constant voltage mode, with the magnesium alloy substrate as the cathode and the stainless steel plate as the anode. The electrophoresis tank temperature is 30 ± 0.5°C, and the voltage is increased to 220 V within 15 s for 5 min to obtain magnesium alloy substrate II.

[0074] S5.3: After the electrophoresis treatment is completed, the obtained magnesium alloy substrate II is cleaned with pure water. After the cleaning is completed, it is baked and solidified. The baking and solidification parameters are a baking temperature of 175° C. and a baking time of 0.5 h.

[0075] Comparative Example 1

[0076] In this comparative example, zirconium nitrate was not added during the inorganic filler modification process, and the remaining steps were consistent with those in Example 1.

[0077] Comparative Example 2

[0078] In this comparative example, no sodium silicate was added during the inorganic filler modification process, and the remaining steps were consistent with those in Example 1.

[0079] Comparative Example 3

[0080] In this comparative example, graphene oxide was not added during the inorganic filler modification process, and the remaining steps were consistent with those in Example 1.

[0081] The examples and comparative examples were subjected to corrosion resistance testing. The corrosion resistance test was performed according to ISO 9227:2017. The sample was fixed and the concentration of 10% sodium chloride was adjusted with 3% hydrochloric acid to a pH of 3 to prepare brine. The brine was sprayed on the sample through a spray device at a spray rate of 20 mL / s, a spray frequency of 60 min / time, and each spray for 20 s. After continuous spraying for 168 h, the corrosion of the sample was observed.

[0082] The experimental results are summarized in the following table:

[0083] Corrosion resistance Example 1 No corrosion, no bubbles Example 2 No corrosion, no bubbles Example 3 No corrosion, no bubbles Comparative Example 1 corrosion Comparative Example 2 No corrosion or bubbles Comparative Example 3 corrosion

[0084] It can be seen from the above experiments that the coating prepared by the present invention can make the magnesium alloy have better corrosion resistance.

[0085] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A magnesium alloy corrosion-resistant coating, characterized in that: The coating formulation is as follows: by mass percentage, epoxy resin 30-40%, phenolic resin 15-20%, modified inorganic filler 5-10%, butanol 15-18%, toluene 10-15%, monoethanolamine 5-7%, dispersant 2-3%, The preparation method of the modified inorganic filler is as follows: S1.1: Titanium dioxide and zirconium nitrate were mixed in a mass ratio of 2:1 and ground in a ball mill at 400 rpm for 1 h. The resulting mixture was transferred to 600°C and calcined for 3 h. After calcination, the mixture was cooled to room temperature and pulverized to obtain Mixture A. S1.2: Sodium silicate is dissolved in deionized water to obtain a sodium silicate solution having a mass fraction of 30-40%. Mixture A is immersed in the sodium silicate solution and ultrasonicated at 40°C for 1-2 hours, wherein the mass ratio of mixture A to sodium silicate is 1:(1-2). After the ultrasonication is completed, the mixture is filtered and dried to obtain mixture B. S1.3: Dissolve graphene oxide in deionized water to obtain a graphene oxide solution with a mass fraction of 40-50%. Immerse mixture B in the graphene oxide solution and sonicate at room temperature for 1 hour. The mass ratio of mixture B to graphene oxide is 1:

1. After the sonication is completed, filter and collect the filter cake. S1.4: Freezing the filter cake in liquid nitrogen for 15 to 20 minutes, and then drying it at -50°C under vacuum for 6 hours. After drying, crushing and grinding the filter cake to obtain the modified inorganic filler. The coating preparation method is as follows: Put epoxy resin, phenolic resin, butanol, toluene and monoethanolamine into a reaction kettle, stir at a speed of 200 r / min, heat to 70°C while stirring, add modified inorganic filler and dispersant after complete dissolution, increase the speed to 250 r / min, stir for 4 to 6 hours, and obtain the coating; The magnesium alloy corrosion-resistant coating is coated on the surface of the micro-arc oxidation coating, and the film thickness of the micro-arc oxidation coating is 8 to 15 μm.

2. The magnesium alloy corrosion-resistant coating according to claim 1, characterized in that: The dispersant is polyethylene glycol, and the number average molecular weight ranges from 2000 to 4000.

3. The magnesium alloy corrosion-resistant coating according to claim 1, characterized in that: The particle size of the mixture A obtained by grinding in S1.1 is 500 mesh.

4. The magnesium alloy corrosion-resistant coating according to claim 1, characterized in that: The particle size of the modified inorganic filler obtained by grinding in S1.4 is 800 mesh.

5. A method for using a magnesium alloy corrosion-resistant coating, based on the magnesium alloy corrosion-resistant coating according to any one of claims 1 to 4, characterized in that: The specific steps of the method of use are as follows: S5.1: Sodium phosphate, sodium fluoride, sodium hydroxide, and deionized water are mixed to form an electrolyte. The cleaned and dried magnesium alloy is placed in an electrolytic cell and subjected to micro-arc oxidation treatment using the magnesium alloy as the anode and the stainless steel plate as the cathode to obtain a magnesium alloy substrate I after micro-arc oxidation treatment. S5.2: Mix cathodic electrophoretic paint KNT831 and corrosion-resistant coating in a mass ratio of 1:1 to obtain a mixture D. Curing the mixture D at 30°C for 24 h, the mixture is then attached to the surface of a magnesium alloy substrate I by electrophoresis treatment to obtain a magnesium alloy substrate II. S5.3: After the electrophoresis treatment is completed, the obtained magnesium alloy substrate II is cleaned with pure water. After cleaning, it is baked and solidified.

6. The method for using the magnesium alloy corrosion-resistant coating according to claim 5, characterized in that: The electrolyte prepared in S5.1 has a sodium phosphate concentration of 10-15 g / L, a sodium fluoride concentration of 4-8 g / L, a sodium hydroxide concentration of 3-6 g / L, and the solvent is deionized water.

7. The method for using the magnesium alloy corrosion-resistant coating according to claim 5, characterized in that: The pH of the electrolyte prepared in S5.1 is 12.9-13.

1.

8. The method for using the magnesium alloy corrosion-resistant coating according to claim 5, characterized in that: The parameters of the micro-arc oxidation treatment in S5.1 are constant current control mode, and the current density is 1.5-2.5A / dm 2 , frequency range is 1000~1500Hz, duty cycle is 25~35%, time is 5~12min, electrolyte temperature is 25~35℃.

9. The method for using the magnesium alloy corrosion-resistant coating according to claim 5, characterized in that: The parameters of the electrophoresis treatment in S5.2 are as follows: constant voltage mode is adopted, the magnesium alloy substrate is the cathode, the stainless steel plate is the anode, the electrophoresis tank temperature is 30±0.5°C, the voltage is controlled to increase to 220V within 15s, and the duration is 5min.

10. The method for using the magnesium alloy corrosion-resistant coating according to claim 5, characterized in that: The baking and curing parameters in S5.3 are a baking temperature of 175° C. and a baking time of 0.5 h.