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

Abstract

The invention belongs to the technical field of metal material surface treatment, and provides a self-hole-sealing and self-healing magnesium alloy corrosion-resistant coating and a preparation method thereof. A micro-arc oxidation coating with self-hole-sealing and self-healing functions is prepared on the surface of the magnesium alloy through a two-step micro-arc oxidation process, so that the corrosion resistance is greatly improved; the technical problems that in the prior art, a micro-arc oxidation coating causes corrosion medium permeation due to the hole structure, the function is single, self-hole-sealing or self-healing is only achieved, the protection effect is limited, and a traditional hole sealing material is prone to aging are solved, and the beneficial effects that long-term active corrosion protection is provided for magnesium alloy, and the technology is simplified are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of surface treatment of metal materials, and particularly 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, magnesium alloys have a density that is only 2 / 3 of aluminum and 1 / 4 of steel, and have characteristics such as high specific strength and excellent vibration damping performance, showing 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 is loose and porous, and cannot 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 limiting 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, TiO 2 ) in the electrolyte, using the particles to fill the pores and reduce the risk of corrosive medium penetration; Second, the self-healing technology: by doping Ce-containing salts (such as cerium acetate), releasing Ce 3+ / Ce 4+ ions during the corrosion process, and reacting with the corrosion products to form a dense protective film (such as Ce(OH) 3 ), 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, making it difficult to meet the industrial requirements. Therefore, there is an urgent need to develop a preparation method for a composite coating 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 micro-arc oxidation coatings 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: (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 drying treatment to obtain a magnesium alloy substrate; (2) Place the magnesium alloy substrate in an alkaline electrolyte solution. Using the magnesium alloy substrate as the anode and a stainless steel container as the cathode, perform micro-arc oxidation treatment in a constant current mode to form a dielectric layer, and obtain a magnesium alloy substrate with a dielectric layer; (3) Transfer the magnesium alloy substrate with a dielectric layer to an electrolyte solution containing cerium salt, 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; The alkaline electrolyte solution includes soluble phosphate and sodium hydroxide; The electrolyte solution containing cerium salt includes soluble phosphate, soluble sodium salt and soluble cerium salt; In the alkaline electrolyte solution, 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 electrolyte solution containing cerium salt, 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 ; 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.

[0007] 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 more of sodium hexametaphosphate, sodium pyrophosphate, sodium phosphate, sodium metaphosphate and potassium phosphate.

[0008] 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 more of sodium fluoride, sodium chloride, sodium carbonate and sodium nitrate.

[0009] 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 cerium salt is any one or more of cerium acetate, cerium nitrate and cerium carbonate.

[0010] According to a preparation method of a self-sealing and self-healing corrosion-resistant coating for magnesium alloy provided by the present invention, the time of micro-arc oxidation treatment in the alkaline electrolyte is 10 to 15 minutes, and the time of micro-arc oxidation treatment in the cerium salt-containing electrolyte is 5 to 20 minutes.

[0011] According to a preparation method of a self-sealing and self-healing corrosion-resistant coating for magnesium alloy provided by 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 to 100 kW.

[0012] According to a preparation method of a self-sealing and self-healing corrosion-resistant coating for magnesium alloy provided by the present invention, the magnesium alloy is a rare earth magnesium alloy or a non-rare earth magnesium alloy.

[0013] According to a preparation method of a self-sealing and self-healing corrosion-resistant coating for magnesium alloy provided by the present invention, the time of ultrasonic cleaning is 20 to 40 minutes.

[0014] On the other hand, the present invention provides a self-sealing and self-healing corrosion-resistant coating for magnesium alloy.

[0015] The self-sealing and self-healing corrosion-resistant coating for magnesium alloy and its preparation method provided by the present invention in-situ dope cerium phosphate on the surface of the magnesium alloy through a two-step micro-arc oxidation process to form a composite coating, solving the technical problems in the prior art such as the penetration of corrosive media due to the hole structure of the micro-arc oxidation coating, 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 the fields of aerospace, automobiles, etc. Description of the Drawings

[0016] 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, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 It is the SEM diagram of the self-sealing and self-healing corrosion-resistant coating for magnesium alloy provided by Embodiment 1 of the present invention; Figure 2 It is the element distribution diagram of the self-sealing and self-healing corrosion-resistant coating for magnesium alloy provided by Embodiment 1 of the present invention; Figure 3It 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; Figure 4 It is the cross-sectional element distribution image of the self-sealing and self-healing corrosion-resistant magnesium alloy coating provided in Embodiment 1 of the present invention; Figure 5 It is the comparison chart of the electrochemical test results of the self-sealing and self-healing corrosion-resistant magnesium alloy coating and the magnesium alloy substrate provided in Embodiment 1 of the present invention; 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

[0018] 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 part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0019] The present invention provides a preparation method for a self-sealing and self-healing corrosion-resistant magnesium alloy coating, including 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 drying treatment to obtain a magnesium alloy substrate; (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; (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 magnesium alloy coating; The alkaline electrolyte includes soluble phosphate and sodium hydroxide; The cerium salt-containing electrolyte includes soluble phosphate, soluble sodium salt, and soluble cerium salt; In the alkaline electrolyte, the concentration of the soluble phosphate is 10~30 g·L -1 , preferably 15~25 g·L -1 , and further preferably 18~22 g·L -1 ; the concentration of the sodium hydroxide is 1~10 g·L -1 , preferably 2~8 g·L -1 , and further preferably 3~7 g·L -1 ; In the cerium salt-containing electrolyte package, the concentration of soluble phosphate is 10-30 g·L -1 , preferably 15-25 g·L -1 , more preferably 18-22 g·L -1 ; the concentration of 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 soluble cerium salt is 1-30 g·L -1 , preferably 5-25 g·L -1 , more preferably 10-20 g·L -1 ; 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.

[0020] In the present invention, the soluble phosphate is any one or several of sodium hexametaphosphate, sodium pyrophosphate, sodium phosphate, sodium metaphosphate, and potassium phosphate, preferably any one or several 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.

[0021] In the present invention, the soluble sodium salt is any one or several of sodium fluoride, sodium chloride, sodium carbonate, and sodium nitrate, preferably any one or several of sodium fluoride, sodium carbonate, and sodium nitrate, and more preferably sodium fluoride or sodium carbonate.

[0022] In the present invention, the soluble cerium salt is any one or several of cerium acetate, cerium nitrate, and cerium carbonate, preferably any one of cerium acetate, cerium nitrate, and cerium carbonate, and more preferably cerium acetate or cerium nitrate.

[0023] In the present invention, the time of the micro-arc oxidation treatment in the alkaline electrolyte is 10-15 min, preferably 11-14 min, more preferably 12-13 min; the time of the micro-arc oxidation treatment in the cerium salt-containing electrolyte is 5-20 min, preferably 10-15 min, more preferably 12-13 min.

[0024] 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, with a power of 10 - 100 kW, preferably 15 - 50 kW, and more preferably 20 - 25 kW.

[0025] In the present invention, the magnesium alloy is a rare-earth magnesium alloy or a non-rare-earth magnesium alloy.

[0026] In the present invention, the time for ultrasonic cleaning is 20 - 40 min, preferably 25 - 35 min, and more preferably 28 - 32 min.

[0027] The present invention also provides a self-sealing and self-healing corrosion-resistant coating for magnesium alloy.

[0028] The technical solutions provided by the present invention will be described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0029] Example 1 The AZ31B magnesium alloy was cut into samples 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, anhydrous ethanol, and acetone for 10 minutes in sequence to obtain a magnesium alloy substrate. 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 20-kW alternating current power supply micro-arc oxidation device was used to perform 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. 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 15 g·L -1 for cerium acetate. The magnesium alloy substrate with a dielectric layer was transferred to the cerium salt-containing electrolyte and subjected to 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. 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 the coating from being ablated due to excessive arc temperature.

[0030] Example 2 Cut the AZ31B magnesium alloy into samples with dimensions of 50 mm × 25 mm × 1 mm. Polish the surface of the aluminum alloy samples with 1500-mesh sandpaper, and then ultrasonically clean them with deionized water, absolute ethanol, and acetone for 10 minutes each to obtain a magnesium alloy substrate; 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 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 AC power micro-arc oxidation device to perform micro-arc oxidation treatment on the surface of the magnesium alloy substrate in a constant-current mode. Control 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, obtaining a magnesium alloy substrate with a dielectric layer; Add sodium hexametaphosphate, sodium fluoride, and cerium acetate to deionized water to prepare a cerium salt-containing electrolyte with a concentration of 20 g·L -1 of sodium hexametaphosphate, 5 g·L -1 of sodium fluoride, and 20 g·L -1 of cerium acetate. Transfer the magnesium alloy substrate with a dielectric layer to the 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 the magnesium alloy. During the micro-arc oxidation process, use circulating water to ensure that the temperature of the electrolyte is between 35 and 40 °C to prevent ablation of the coating caused by excessive arc temperature.

[0031] Example 3 Cut the AZ31B magnesium alloy into samples with dimensions of 50 mm × 25 mm × 1 mm. Polish the surface of the aluminum alloy samples with 1500-mesh sandpaper, and then ultrasonically clean them with deionized water, absolute ethanol, and acetone for 10 minutes each to obtain a magnesium alloy substrate; 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 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 AC power micro-arc oxidation device to perform micro-arc oxidation treatment on the surface of the magnesium alloy substrate in a constant-current mode. Control 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, obtaining a magnesium alloy substrate with a dielectric layer; Add sodium hexametaphosphate, sodium fluoride, and cerium acetate to deionized water to prepare a cerium salt-containing electrolyte with a concentration of 20 g·L -1, the concentration of sodium fluoride is 5 g·L -1 , the concentration of cerium acetate is 25 g·L -1 of the cerium salt electrolyte. Transfer the magnesium alloy substrate with a dielectric layer to the cerium salt electrolyte, and perform micro-arc oxidation treatment again under the same constant current mode to obtain a self-sealing and self-healing corrosion-resistant magnesium alloy coating. During the micro-arc oxidation process, circulating water is used to ensure that the temperature of the electrolyte is between 35 and 40 °C to prevent the coating from being ablated due to excessive arc temperature.

[0032] The following combines Figures 1 to 6 to describe the self-sealing and self-healing corrosion-resistant magnesium alloy coating of the present invention and its preparation method.

[0033] Figure 1 is the SEM image of the self-sealing and self-healing corrosion-resistant magnesium alloy coating provided in Example 1 of the present invention.

[0034] As Figure 1 shown, for the self-sealing and self-healing corrosion-resistant magnesium alloy coating 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. By magnifying the 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, and the hole-sealing effect is more significant.

[0035] Figure 2 is the element distribution map of the self-sealing and self-healing corrosion-resistant magnesium alloy coating provided in Example 1 of the present invention.

[0036] As Figure 2 shown, according to the elemental analysis of the hole-filling substances on the surface, it can be seen that Ce element is distributed in the coating, indicating the in-situ generation of cerium phosphate. In addition, Ce element is also enriched in the holes. This is the molten mixture of cerium phosphate and magnesium oxide generated by the specific electrolyte under the discharge state. It can be seen that the hole-sealing effect of the coating is significant. And the multivalent state of Ce element has a corrosion self-healing effect. When there is a corrosive medium in the holes of the coating, cerium phosphate will release Ce 3+ and generate Ce(OH) 3 , and play the self-healing performance.

[0037] Figure 3 is the cross-sectional SEM image of the self-sealing and self-healing corrosion-resistant magnesium alloy coating provided in Example 1 of the present invention.

[0038] As Figure 3As shown, the cross-sectional picture of the near-surface of the self-sealing and self-healing magnesium alloy corrosion-resistant coating provided in Embodiment 1 of the present invention clearly shows that the open holes generated by discharge breakdown are filled with the molten mixture, but the small closed air holes inside are not filled. This is caused by the gas generated by the plasma reaction during the coating growth process. Since this area has not undergone a violent discharge breakdown reaction, the holes are small and closed, so the presence or absence of fillers does not affect the corrosion resistance of the coating.

[0039] Figure 4 It is the cross-sectional element distribution diagram of the self-sealing and self-healing magnesium alloy corrosion-resistant coating provided in Embodiment 1 of the present invention.

[0040] As Figure 4 shown, by performing EDS element analysis on the cross-section of the near-surface of the self-sealing and self-healing magnesium alloy corrosion-resistant coating provided in Embodiment 1 of the present invention, it can be seen that the Ce element representing the filler is enriched in the holes, and there are also Mg, O, and P elements present at the same time. This indicates that the filler inside the holes is mainly a mixture containing cerium phosphate.

[0041] Figure 5 It is the comparison diagram of the electrochemical test results of the self-sealing and self-healing magnesium alloy corrosion-resistant coating provided in Embodiment 1 of the present invention and the magnesium alloy substrate.

[0042] 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 Embodiment 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, so it shows a better corrosion resistance effect.

[0043] Figure 6 It 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 Embodiment 1 of the present invention after 14 days of immersion in brine.

[0044] As Figure 6 shown, the results of the self-sealing and self-healing magnesium alloy corrosion-resistant coating provided in Embodiment 1 of the present invention after being immersed in a 3.5% mass fraction sodium chloride solution for 14 days show that a large number of nanoparticles appear on the surface and in the holes of the coating. This indicates that the cerium phosphate in the coating surface and holes reacts to form the corrosion product Ce(OH) 3 , exerting the self-healing performance. At the same time, it also increases the traditional corrosion product Mg(OH) 2The compactness is such that no local corrosion pits appear on the coating, and the corrosion resistance is greatly enhanced. Among them, the formula of the brine is: an aqueous solution of sodium chloride with a mass fraction of 3.5%, specifically, 3.5 g of NaCl powder is dissolved in 97 g of distilled water; the process conditions for soaking are: the test is tied with a thin fishing line and then completely immersed in a 1 L beaker containing 500 mL of an aqueous solution of sodium chloride with a mass fraction of 3.5%, the ambient temperature is maintained at 25 °C, and the humidity is maintained at 45%.

[0045] 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 recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a self-sealing and self-healing magnesium alloy corrosion-resistant coating, characterized in that: The following steps are involved: (1) performing surface pretreatment on the magnesium alloy, wherein the surface pretreatment comprises mechanical polishing, deionized water cleaning, anhydrous ethanol and acetone ultrasonic cleaning, and drying to obtain a magnesium alloy matrix; (2) placing the magnesium alloy substrate in an alkaline electrolyte, using the magnesium alloy substrate as an anode and the stainless steel container as a cathode, and performing micro-arc oxidation treatment in a constant current mode to form a dielectric layer, thereby obtaining a magnesium alloy substrate with a dielectric layer; (3) transferring the magnesium alloy substrate with the dielectric layer into a cerium salt-containing electrolyte, and performing micro-arc oxidation treatment again under the same constant current mode to obtain a self-sealing and self-healing magnesium alloy corrosion-resistant coating; The alkaline electrolyte includes soluble phosphate and sodium hydroxide; The cerium salt-containing electrolyte includes a soluble phosphate, a soluble sodium salt and a soluble cerium salt; In the alkaline electrolyte, the concentration of soluble phosphate is 10-30 g·L -1 , the concentration of sodium hydroxide is 1~10 g·L -1 ; The concentration of soluble phosphate in the cerium salt electrolyte package is 10-30 g·L -1 , the concentration of soluble sodium salt is 1~10 g·L -1 , the concentration of soluble cerium salt is 1~30 g·L -1 ; The current density of the micro-arc oxidation treatment is 1-15A·dm -2 , frequency is 200~2000Hz, duty cycle is 10~30%, total reaction time is 5~30min, electrolyte temperature is ≤40℃.

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

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

4. The method for preparing the self-sealing and self-healing magnesium alloy corrosion-resistant coating according to claim 1, characterized in that: The soluble cerium salt is any one or more of cerium acetate, cerium nitrate and cerium carbonate.

5. The method for preparing the self-sealing and self-healing magnesium alloy corrosion-resistant coating according to claim 1, characterized in that: The time of micro-arc oxidation treatment in the alkaline electrolyte is 10 to 15 minutes, and the time of micro-arc oxidation treatment in the cerium salt-containing electrolyte is 5 to 20 minutes.

6. The method for preparing the self-sealing and self-healing magnesium alloy corrosion-resistant coating according to claim 1, characterized in that: The power source for the micro-arc oxidation treatment is an AC power source or a DC power source with a power of 10-100 kW.

7. The method for preparing the self-sealing and self-healing magnesium alloy corrosion-resistant coating according to claim 1, characterized in that: The magnesium alloy is a rare earth magnesium alloy or a non-rare earth magnesium alloy.

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

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

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