Self-sealing and self-healing corrosion-resistant magnesium alloy coating and its preparation method

Abstract

The present invention belongs to the technical field of surface treatment of metal materials, and provides a self-sealing and self-healing corrosion-resistant coating for magnesium alloys and a preparation method thereof. A micro-arc oxidation coating with both self-sealing and self-healing functions is prepared on the surface of the magnesium alloy through a two-step micro-arc oxidation process, greatly improving the corrosion resistance, solving the technical problems in the prior art such as the penetration of corrosive media due to the pore structure of the micro-arc oxidation coating, single functions of only self-sealing or self-healing, limited protection effect, and easy aging of traditional sealing materials, and achieving the beneficial effects of providing long-term active corrosion protection for magnesium alloys and simplifying the process.

Description

Technical Field

[0001] The present invention relates to the technical field of surface treatment of metal materials, and particularly relates to a self-sealing and self-healing corrosion-resistant coating for magnesium alloys and a preparation method thereof. Background Art

[0002] As the lightest metal structural material, the density of magnesium alloy is only 2 / 3 of that of aluminum and 1 / 4 of that of steel. It has characteristics such as high specific strength and excellent vibration damping performance, and shows great application potential in fields such as aerospace and automotive lightweighting. However, the standard electrode potential of magnesium is extremely low (-2.37V), and its corrosion product Mg(OH)2 film layer is loose and porous, unable to effectively block the long-term erosion of corrosive media. Especially in magnesium alloys containing high-potential second phases (such as Mg 17 Al 12 , Al-Mn phase), the problem of galvanic corrosion is more prominent, severely restricting its engineering applications in harsh environments.

[0003] Currently, micro-arc oxidation (MAO) technology is widely used for the surface protection of magnesium alloys, and the corrosion resistance is significantly improved by in-situ generating a ceramic coating. To further solve the pore defects of the micro-arc oxidation coating, two types of improvement schemes have been proposed in the prior art: First, the self-sealing hole technology: doping corrosion-resistant nanoparticles (such as ZnO, TiO2) in the electrolyte, using the particles to fill the pores and reducing the risk of corrosive medium penetration; Second, the self-healing technology: by doping a Ce salt (such as cerium acetate), releasing Ce 3+ / Ce 4+ ions during the corrosion process, reacting with the corrosion products to form a dense protective film (such as Ce(OH)3) and delaying the corrosion of the substrate.

[0004] However, there are still technical defects in the prior art. For example: in the self-sealing hole technology, the nanoparticles can only temporarily fill the pores, and the gaps between the particles will still cause the penetration of corrosive media during long-term service, and the mechanical stability of the nanostructure is insufficient; in the self-healing technology, although the cerium-containing coating can achieve dynamic repair, it cannot solve the problem of rapid penetration of corrosive media by the initial pore defects; the traditional scheme requires separate implementation of the sealing and self-healing treatments for the preparation of the self-sealing hole and self-healing coatings, with a cumbersome process and high cost, and it is difficult to meet the industrial requirements. Therefore, there is an urgent need to develop a composite coating preparation method with both self-sealing hole and self-healing functions to comprehensively improve the long-term corrosion resistance of magnesium alloys. Summary of the Invention

[0005] The present invention provides a self-sealing and self-healing corrosion-resistant coating for magnesium alloys and a preparation method thereof, aiming to solve the technical problems of single function, limited protection effect and complex process of the micro-arc oxidation coating in the prior art.

[0006] On the one hand, the present invention provides a method for preparing a self-sealing and self-healing corrosion-resistant coating for magnesium alloy, comprising the following steps:

[0007] (1) Perform surface pretreatment on the magnesium alloy. The surface pretreatment is successively mechanical polishing, deionized water cleaning, ultrasonic cleaning with anhydrous ethanol and acetone, and then perform drying treatment to obtain a magnesium alloy substrate;

[0008] (2) Place the magnesium alloy substrate in an alkaline electrolyte, use the magnesium alloy substrate as the anode and a stainless-steel container as the cathode, and perform micro-arc oxidation treatment in a constant current mode to form a dielectric layer, obtaining a magnesium alloy substrate with a dielectric layer;

[0009] (3) Transfer the magnesium alloy substrate with a dielectric layer to a cerium salt-containing electrolyte, and perform micro-arc oxidation treatment again in the same constant current mode to obtain a self-sealing and self-healing corrosion-resistant coating for magnesium alloy;

[0010] The alkaline electrolyte includes soluble phosphate and sodium hydroxide;

[0011] The cerium salt-containing electrolyte includes soluble phosphate, soluble sodium salt, and soluble cerium salt;

[0012] In the alkaline electrolyte, the concentration of soluble phosphate is 10-30 g·L -1 and the concentration of sodium hydroxide is 1-10 g·L -1 ;

[0013] In the cerium salt-containing electrolyte package, the concentration of soluble phosphate is 10-30 g·L -1 the concentration of soluble sodium salt is 1-10 g·L -1 and the concentration of soluble cerium salt is 1-30 g·L -1 ;

[0014] The current density of the micro-arc oxidation treatment is 1-15 A·dm -2 with a frequency of 200-2000 Hz, a duty cycle of 10-30%, a total reaction time of 5-30 min, and the electrolyte temperature ≤ 40°C.

[0015] According to the method for preparing a self-sealing and self-healing corrosion-resistant coating for magnesium alloy provided by the present invention, the soluble phosphate is any one or several of sodium hexametaphosphate, sodium pyrophosphate, sodium phosphate, sodium metaphosphate, and potassium phosphate.

[0016] According to the method for preparing a self-sealing and self-healing corrosion-resistant coating for magnesium alloy provided by the present invention, the soluble sodium salt is any one or several of sodium fluoride, sodium chloride, sodium carbonate, and sodium nitrate.

[0017] A preparation method of a self-sealing and self-healing corrosion-resistant coating for magnesium alloy provided by the present invention, wherein the soluble cerium salt is any one or more of cerium acetate, cerium nitrate, and cerium carbonate.

[0018] A preparation method of a self-sealing and self-healing corrosion-resistant coating for magnesium alloy provided by the present invention, wherein the time of micro-arc oxidation treatment in the alkaline electrolyte is 10 - 15 min, and the time of micro-arc oxidation treatment in the cerium salt-containing electrolyte is 5 - 20 min.

[0019] A preparation method of a self-sealing and self-healing corrosion-resistant coating for magnesium alloy provided by the present invention, wherein the power supply for micro-arc oxidation treatment is an alternating current power supply or a direct current power supply, and the power is 10 - 100 kW.

[0020] A preparation method of a self-sealing and self-healing corrosion-resistant coating for magnesium alloy provided by the present invention, wherein the magnesium alloy is a rare earth magnesium alloy or a non-rare earth magnesium alloy.

[0021] A preparation method of a self-sealing and self-healing corrosion-resistant coating for magnesium alloy provided by the present invention, wherein the time of ultrasonic cleaning is 20 - 40 min.

[0022] On the other hand, the present invention provides a self-sealing and self-healing corrosion-resistant coating for magnesium alloy.

[0023] The self-sealing and self-healing corrosion-resistant coating for magnesium alloy provided by the present invention and its preparation method in-situ dope cerium phosphate on the surface of magnesium alloy through a two-step micro-arc oxidation process to form a composite coating, solving the technical problems in the prior art that the micro-arc oxidation coating has corrosion medium penetration due to hole structure, single function of only self-sealing or self-healing, limited protection effect, and easy aging of traditional sealing materials, achieving the self-sealing function and significantly improving the coating density; the self-healing function, dynamically repairing coating defects and extending the protection life; the two-step micro-arc oxidation process integrates the self-sealing and self-healing functions, without the need for additional sealing treatment, reducing the process complexity and cost; being applicable to rare earth and non-rare earth magnesium alloy systems, expanding the application potential of lightweight materials in fields such as aerospace and automotive. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 It is a SEM diagram of the self-sealing and self-healing corrosion-resistant coating for magnesium alloy provided by Embodiment 1 of the present invention;

[0026] Figure 2 It is the elemental distribution map of the self-sealing and self-healing corrosion-resistant magnesium alloy coating provided in Embodiment 1 of the present invention;

[0027] Figure 3 It is the cross-sectional SEM image of the self-sealing and self-healing corrosion-resistant magnesium alloy coating provided in Embodiment 1 of the present invention;

[0028] Figure 4 It is the cross-sectional elemental distribution map of the self-sealing and self-healing corrosion-resistant magnesium alloy coating provided in Embodiment 1 of the present invention;

[0029] Figure 5 It is the comparison chart of the electrochemical test results between the self-sealing and self-healing corrosion-resistant magnesium alloy coating provided in Embodiment 1 of the present invention and the magnesium alloy substrate;

[0030] Figure 6 It is the SEM image of the surface corrosion self-healing morphology of the self-sealing and self-healing corrosion-resistant magnesium alloy coating provided in Embodiment 1 of the present invention after 14 days of immersion in brine. Detailed implementation manners

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts fall within the scope of protection of the present invention.

[0032] The present invention provides a preparation method for a self-sealing and self-healing corrosion-resistant magnesium alloy coating, including the following steps:

[0033] (1) Perform surface pretreatment on the magnesium alloy. The surface pretreatment is successively mechanical polishing, deionized water cleaning, ultrasonic cleaning with absolute ethanol and acetone, and drying treatment to obtain a magnesium alloy substrate;

[0034] (2) Place the magnesium alloy substrate in an alkaline electrolyte solution, use the magnesium alloy substrate as the anode and a stainless steel container as the cathode, and perform micro-arc oxidation treatment in a constant current mode to form a dielectric layer, obtaining a magnesium alloy substrate with a dielectric layer;

[0035] (3) Transfer the magnesium alloy substrate with the dielectric layer to a cerium salt-containing electrolyte solution, and perform micro-arc oxidation treatment again in the same constant current mode to obtain a self-sealing and self-healing corrosion-resistant magnesium alloy coating;

[0036] The alkaline electrolyte solution includes soluble phosphate and sodium hydroxide;

[0037] The cerium salt-containing electrolyte includes soluble phosphate, soluble sodium salt, and soluble cerium salt;

[0038] In the alkaline electrolyte, the concentration of the soluble phosphate is 10-30 g·L -1 , preferably 15-25 g·L -1 , more preferably 18-22 g·L -1 ; the concentration of sodium hydroxide is 1-10 g·L -1 , preferably 2-8 g·L -1 , more preferably 3-7 g·L -1 ;

[0039] In the cerium salt-containing electrolyte package, the concentration of the soluble phosphate is 10-30 g·L -1 , preferably 15-25 g·L -1 , more preferably 18-22 g·L -1 ; the concentration of the soluble sodium salt is 1-10 g·L -1 , preferably 2-8 g·L -1 , more preferably 4-6 g·L -1 ; the concentration of the soluble cerium salt is 1-30 g·L -1 , preferably 5-25 g·L -1 , more preferably 10-20 g·L -1 ;

[0040] The current density of the micro-arc oxidation treatment is 1-15 A·dm -2 , preferably 3-13 A·dm -2 , more preferably 5-10 A·dm -2 ; the frequency is 200-2000 Hz, preferably 200-1000 Hz, more preferably 200-500 Hz; the duty cycle is 10-30%, preferably 11-20%, more preferably 12-15%; the total reaction time is 5-30 min, and the electrolyte temperature ≤ 40 °C.

[0041] In the present invention, the soluble phosphate is any one or more of sodium hexametaphosphate, sodium pyrophosphate, sodium phosphate, sodium metaphosphate, and potassium phosphate, preferably any one or more of sodium hexametaphosphate, sodium pyrophosphate, sodium phosphate, and sodium metaphosphate, and more preferably any one of sodium hexametaphosphate, sodium pyrophosphate, sodium phosphate, and sodium metaphosphate.

[0042] In the present invention, the soluble sodium salt is any one or more of sodium fluoride, sodium chloride, sodium carbonate, and sodium nitrate, preferably any one or more of sodium fluoride, sodium carbonate, and sodium nitrate, and more preferably sodium fluoride or sodium carbonate.

[0043] In the present invention, the soluble cerium salt is any one or more of cerium acetate, cerium nitrate and cerium carbonate, preferably any one of cerium acetate, cerium nitrate and cerium carbonate, and further preferably cerium acetate or cerium nitrate.

[0044] In the present invention, the time of micro-arc oxidation treatment in the alkaline electrolyte is 10 - 15 min, preferably 11 - 14 min, and further preferably 12 - 13 min; the time of micro-arc oxidation treatment in the cerium salt-containing electrolyte is 5 - 20 min, preferably 10 - 15 min, and further preferably 12 - 13 min.

[0045] In the present invention, the power supply for the micro-arc oxidation treatment is an alternating current power supply or a direct current power supply, and the power is 10 - 100 kW, preferably 15 - 50 kW, and further preferably 20 - 25 kW.

[0046] In the present invention, the magnesium alloy is a rare earth magnesium alloy or a non-rare earth magnesium alloy.

[0047] In the present invention, the time of ultrasonic cleaning is 20 - 40 min, preferably 25 - 35 min, and further preferably 28 - 32 min.

[0048] The present invention also provides a self-sealing and self-healing corrosion-resistant coating for magnesium alloy.

[0049] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0050] Example 1

[0051] Cut an AZ31B magnesium alloy into samples of 50 mm × 25 mm × 1 mm, polish the surface of the aluminum alloy sample with 1500-mesh sandpaper, and then ultrasonically clean it with deionized water, absolute ethanol and acetone for 10 minutes in sequence to obtain a magnesium alloy substrate;

[0052] Add sodium hexametaphosphate and sodium hydroxide to deionized water to prepare an alkaline electrolyte with a concentration of 20 g·L -1 of sodium hexametaphosphate and a concentration of 3 g·L -1 of sodium hydroxide. Place the magnesium alloy substrate in the alkaline electrolyte, use the magnesium alloy substrate as the anode and a stainless steel container as the cathode, and adopt a 20-kW alternating current power supply micro-arc oxidation device to perform micro-arc oxidation treatment on the surface of the magnesium alloy substrate in a constant current mode, controlling the current density to be 5.5 A·dm -2 , the frequency to be 200 Hz, the duty cycle to be 12%, and the discharge time to be 12 minutes to form a dielectric layer, and obtain a magnesium alloy substrate with a dielectric layer;

[0053] Sodium hexametaphosphate, sodium fluoride and cerium acetate were added to deionized water to prepare an electrolyte containing cerium salts with a concentration of 20 g·L of sodium hexametaphosphate -1 , 5 g·L of sodium fluoride -1 and 15 g·L of cerium acetate -1 . The magnesium alloy substrate with a dielectric layer was transferred to the electrolyte containing cerium salts, and micro-arc oxidation treatment was carried out again under the same constant current mode to obtain a self-sealing and self-healing corrosion-resistant coating on the magnesium alloy. During the micro-arc oxidation process, circulating water was used to ensure that the temperature of the electrolyte was maintained at 35-40 °C to prevent ablation of the coating caused by excessive arc temperature.

[0054] Example 2

[0055] AZ31B magnesium alloy was cut into samples with dimensions of 50 mm × 25 mm × 1 mm. The surface of the aluminum alloy samples was polished with 1500-mesh sandpaper, and then ultrasonically cleaned with deionized water, absolute ethanol and acetone for 10 minutes in sequence to obtain a magnesium alloy substrate;

[0056] Sodium hexametaphosphate and sodium hydroxide were added to deionized water to prepare an alkaline electrolyte with a concentration of 20 g·L of sodium hexametaphosphate -1 and 3 g·L of sodium hydroxide -1 . The magnesium alloy substrate was placed in the alkaline electrolyte. Using the magnesium alloy substrate as the anode and a stainless steel container as the cathode, a 20 kW AC power supply micro-arc oxidation device was used to carry out micro-arc oxidation treatment on the surface of the magnesium alloy substrate in a constant current mode, controlling the current density at 5.5 A·dm -2 , the frequency at 200 Hz, the duty cycle at 12%, and the discharge time at 12 minutes to form a dielectric layer, obtaining a magnesium alloy substrate with a dielectric layer;

[0057] Sodium hexametaphosphate, sodium fluoride and cerium acetate were added to deionized water to prepare an electrolyte containing cerium salts with a concentration of 20 g·L of sodium hexametaphosphate -1 , 5 g·L of sodium fluoride -1 and 20 g·L of cerium acetate -1 . The magnesium alloy substrate with a dielectric layer was transferred to the electrolyte containing cerium salts, and micro-arc oxidation treatment was carried out again under the same constant current mode to obtain a self-sealing and self-healing corrosion-resistant coating on the magnesium alloy. During the micro-arc oxidation process, circulating water was used to ensure that the temperature of the electrolyte was maintained at 35-40 °C to prevent ablation of the coating caused by excessive arc temperature.

[0058] Example 3

[0059] The AZ31B magnesium alloy was cut into samples with dimensions of 50 mm × 25 mm × 1 mm. The surface of the aluminum alloy samples was polished with 1500-mesh sandpaper, and then ultrasonically cleaned with deionized water, absolute ethanol, and acetone for 10 minutes each to obtain the magnesium alloy substrate.

[0060] Sodium hexametaphosphate and sodium hydroxide were added to deionized water to prepare an alkaline electrolyte with a concentration of 20 g·L -1 for sodium hexametaphosphate and 3 g·L -1 for sodium hydroxide. The magnesium alloy substrate was placed in the alkaline electrolyte. Using the magnesium alloy substrate as the anode and a stainless-steel container as the cathode, a micro-arc oxidation device with a 20 kW AC power supply was employed to perform micro-arc oxidation treatment on the surface of the magnesium alloy substrate in a constant current mode. The current density was controlled at 5.5 A·dm -2 , the frequency was 200 Hz, the duty cycle was 12%, and the discharge time was 12 minutes to form a dielectric layer, obtaining a magnesium alloy substrate with a dielectric layer.

[0061] Sodium hexametaphosphate, sodium fluoride, and cerium acetate were added to deionized water to prepare a cerium salt-containing electrolyte with a concentration of 20 g·L -1 for sodium hexametaphosphate, 5 g·L -1 for sodium fluoride, and 25 g·L -1 for cerium acetate. The magnesium alloy substrate with the dielectric layer was transferred to the cerium salt-containing electrolyte and micro-arc oxidation treatment was performed again in the same constant current mode to obtain a self-sealing and self-healing corrosion-resistant coating for magnesium alloy. During the micro-arc oxidation process, circulating water was used to ensure that the temperature of the electrolyte was maintained at 35 - 40 °C to prevent ablation of the coating caused by excessive arc temperature.

[0062] The following will describe Figures 1 to 6 the self-sealing and self-healing corrosion-resistant coating for magnesium alloy of the present invention and its preparation method.

[0063] Figure 1 Figure

[0064] As Figure 1 shown, for the self-sealing and self-healing corrosion-resistant coating for magnesium alloy provided in Example 1 of the present invention, it can be seen from the low magnification of the surface that holes of different sizes are filled with substances. Upon magnified observation, it is found that the filling substances are mainly the melt generated during the discharge process, including the nanoparticles in-situ generated in the solution, and they are bonded together under the high-temperature environment of local discharge, resulting in a more significant hole-sealing effect.

[0065] Figure 2 Figure

[0066] AsFigure 2 As shown, according to the analysis of the elemental composition of the pore-filling substances on the surface, it can be seen that Ce elements are distributed throughout the coating, indicating the in-situ formation of cerium phosphate. In addition, Ce elements are enriched within the pores. This is a molten mixture of cerium phosphate and magnesium oxide generated by a specific electrolyte under the discharge state. Thus, it can be seen that the pore-sealing effect of the coating is remarkable. The multivalent state of Ce elements has a corrosion self-healing effect. When there are corrosive media within the pores of the coating, cerium phosphate will release Ce 3+ and generate Ce(OH)3, thereby exerting the self-healing performance.

[0067] Figure 3 This is the cross-sectional SEM image of the self-sealing and self-healing magnesium alloy corrosion-resistant coating provided in Example 1 of the present invention.

[0068] As Figure 3 shown, for the self-sealing and self-healing magnesium alloy corrosion-resistant coating provided in Example 1 of the present invention, the cross-sectional image near the surface clearly shows that the open pores generated by discharge breakdown are filled with the molten mixture, but the small internal closed air pores are not filled. This is caused by the gas generated during the plasma reaction in the coating growth process. Since this area has not undergone an intense discharge breakdown reaction, the pores are small and closed, so the presence or absence of fillers does not affect the corrosion resistance of the coating.

[0069] Figure 4 This is the cross-sectional element distribution diagram of the self-sealing and self-healing magnesium alloy corrosion-resistant coating provided in Example 1 of the present invention.

[0070] As Figure 4 shown, by performing EDS elemental analysis on the cross-section near the surface of the self-sealing and self-healing magnesium alloy corrosion-resistant coating provided in Example 1 of the present invention, it can be seen that the Ce element representing the filler is enriched in the pores. At the same time, there are also Mg, O, and P elements present. This indicates that the filler within the pores is mainly a mixture containing cerium phosphate.

[0071] Figure 5 This is the comparison chart of the electrochemical test results between the self-sealing and self-healing magnesium alloy corrosion-resistant coating provided in Example 1 of the present invention and the magnesium alloy substrate.

[0072] As Figure 5 shown, by comparing with the electrochemical results of the magnesium alloy substrate, it can be known that the corrosion potential of the self-sealing and self-healing magnesium alloy corrosion-resistant coating provided in Example 1 of the present invention is more positive and the corrosion current density is smaller, indicating that the resistance of the solution to the corrosion of the coating is greater. Therefore, it shows a better corrosion resistance effect.

[0073] Figure 6 This is the SEM image of the surface corrosion self-healing morphology of the self-sealing and self-healing magnesium alloy corrosion-resistant coating provided in Example 1 of the present invention after 14 days of immersion in brine.

[0074] As Figure 6 shown, the results after the self-sealing and self-healing magnesium alloy corrosion-resistant coating provided in Embodiment 1 of the present invention was immersed in a sodium chloride solution with a mass fraction of 3.5% for 14 days showed that a large number of nanoparticles appeared on the surface, holes and surface of the coating. This indicates that cerium phosphate in the coating surface and holes reacted to form the corrosion product Ce(OH)3, which exerted the self-healing performance. At the same time, the compactness of the traditional corrosion product Mg(OH)2 was also increased. Therefore, no local corrosion pits appeared on the coating, and the corrosion resistance was greatly enhanced. Among them, the formula of the brine is: an aqueous sodium chloride solution with a mass fraction of 3.5%, specifically, 3.5 g of NaCl powder is dissolved in 97 g of distilled water; the immersion process conditions are: the test is bundled with a thin fishing line and then completely immersed in a 1 L beaker containing 500 mL of an aqueous sodium chloride solution with a mass fraction of 3.5%, the ambient temperature is maintained at 25 °C, and the humidity is maintained at 45%.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of a self-sealing and self-healing corrosion-resistant coating for magnesium alloy, characterized in that, It includes the following steps: (1) Perform surface pretreatment on the magnesium alloy. The surface pretreatment is successively mechanical polishing, deionized water cleaning, ultrasonic cleaning with anhydrous ethanol and acetone, and then perform drying treatment to obtain a magnesium alloy substrate; (2) Place the magnesium alloy substrate in an alkaline electrolyte solution. Use the magnesium alloy substrate as the anode and a stainless steel container as the cathode, and perform micro-arc oxidation treatment in a constant current mode to form a dielectric layer, obtaining a magnesium alloy substrate with a dielectric layer; (3) Transfer the magnesium alloy substrate with a dielectric layer to a cerium salt-containing electrolyte solution, and perform micro-arc oxidation treatment again in the same constant current mode to obtain a self-sealing and self-healing magnesium alloy corrosion-resistant coating; The alkaline electrolyte solution includes soluble phosphate and sodium hydroxide; The cerium salt-containing electrolyte solution includes soluble phosphate, soluble sodium salt and soluble cerium salt; In the alkaline electrolyte, the concentration of soluble phosphate is 10 - 30 g·L -1 , and the concentration of sodium hydroxide is 1 - 10 g·L -1 ; In the cerium salt-containing electrolyte, the concentration of soluble phosphate is 10 to 30 g·L -1 , the concentration of soluble sodium salt is 1 to 10 g·L -1 , and the concentration of soluble cerium salt is 1 to 30 g·L -1 ; The current density of the micro-arc oxidation treatment is 1~15 A·dm -2 , the frequency is 200~2000 Hz, the duty cycle is 10~30%, the total reaction time is 5~30 min, and the electrolyte temperature ≤ 40°C.

2. The preparation method of the self-sealing and self-healing corrosion-resistant magnesium alloy coating according to claim 1, characterized in that, The soluble phosphate is any one or several of sodium hexametaphosphate, sodium pyrophosphate, sodium phosphate and potassium phosphate.

3. The preparation method of the self-sealing and self-healing corrosion-resistant magnesium alloy coating according to claim 1, characterized in that, The soluble sodium salt is any one or several of sodium fluoride, sodium chloride, sodium carbonate and sodium nitrate.

4. The preparation method of the self-sealing and self-healing corrosion-resistant magnesium alloy coating according to claim 1, characterized in that, The soluble cerium salt is cerium acetate and / or cerium nitrate.

5. The preparation method of the self-sealing and self-healing corrosion-resistant magnesium alloy coating according to claim 1, characterized in that, The time for micro-arc oxidation treatment in the alkaline electrolyte solution is 10 - 15 min, and the time for micro-arc oxidation treatment in the cerium salt-containing electrolyte solution is 5 - 15 min.

6. The preparation method of the self-sealing and self-healing corrosion-resistant magnesium alloy coating according to claim 1, characterized in that, The power supply for the micro-arc oxidation treatment is an alternating current power supply or a direct current power supply, and the power is 10 - 100 kW.

7. The preparation method of the self-sealing and self-healing corrosion-resistant magnesium alloy coating according to claim 1, wherein, The magnesium alloy is a rare earth magnesium alloy or a non-rare earth magnesium alloy.

8. The preparation method of the self-sealing and self-healing corrosion-resistant magnesium alloy coating according to claim 1, characterized in that, The time for ultrasonic cleaning is 20 - 40 min.

9. A self-sealing and self-healing corrosion-resistant coating for magnesium alloy, characterized in that, The magnesium alloy corrosion-resistant coating is prepared by the preparation method described in any one of claims 1 - 8.

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