Magnesium alloy surface conductive corrosion-resistant coating, preparation method and modified magnesium alloy

Abstract

The invention belongs to the technical field of metal material surface modification, and particularly relates to a magnesium alloy surface conductive corrosion-resistant coating and a preparation method, the conductive corrosion-resistant coating comprises a three-layer structure, the total coating thickness is 33-50 microns, the bottom coating is a low-porosity MAO coating prepared through a micro-arc oxidation method, and the thickness is 20-35 microns; the middle coating is a conductive nano-particle layer prepared by adopting a negative pressure mode; and the top coating is a zinc aluminum oxide conductive layer prepared by adopting a vapor-phase hydrothermal deposition method, and the thickness of the top coating is 13-15 microns. In addition, the invention provides the modified magnesium alloy with the conductive corrosion-resistant coating prepared on the surface, the self-corrosion current density of the modified magnesium alloy is 0.18-1.8 * 10 <-7 > A / cm < 2 >, and the volume resistivity of the modified magnesium alloy is 1.30-5.21 * 10 < 4 > omega.m.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface modification of metal materials, and particularly relates to a conductive and corrosion-resistant coating on the surface of a magnesium alloy, a preparation method, and a modified magnesium alloy. Background Art

[0002] Due to its excellent lightweight performance, magnesium alloy has attracted much attention in electronic equipment such as missile guidance antenna housings and radar antennas. As one of the lightest metal structural materials, magnesium alloy effectively realizes the lightweight of equipment. However, due to its high chemical and electrochemical activity, magnesium alloy has a strong corrosion tendency in the natural environment, especially in a high-humidity environment, where corrosion will be accelerated, which is not conducive to the normal use of products.

[0003] Surface coating is an effective way to improve the corrosion resistance of magnesium alloy. However, in the actual research and development and application process of the existing surface protection coating technology for magnesium alloy, it often focuses too much on improving the corrosion resistance of materials, and even sets enhancing corrosion resistance as the primary or even the only goal. To a certain extent, it ignores, or even sacrifices, the electrical conductivity characteristics inherent in the material itself.

[0004] At present, the treatment processes for surface protection coatings of magnesium alloy are rich and diverse. Among them, micro-arc oxidation technology, as an advanced surface treatment process, can, on the surfaces of metals such as magnesium, aluminum, and titanium, by means of the instant high temperature and high pressure environment triggered by arc discharge, promote the oxidation reaction of the substrate metal, and then grow a ceramic coating mainly composed of the substrate oxide. Therefore, micro-arc oxidation technology has been widely used in the protection fields of various materials such as magnesium alloy due to many significant advantages, such as extremely high bonding strength between the coating and the substrate, dense and pore-free structure, good toughness, excellent wear resistance, and outstanding high-temperature resistance. However, when magnesium alloy military electronic equipment is treated by micro-arc oxidation technology, its surface will show insulating properties. This situation not only limits the application scope of magnesium alloy to a certain extent, making it difficult to expand to more fields that require electrical conductivity, but also may cause potential safety hazards due to the insulating properties in the existing application fields, posing a threat to the normal operation and reliability of the equipment.

[0005] Therefore, the research on surface modification technology with both anti-corrosion and conductive functions is of particularly important practical significance for the application of magnesium alloy, especially for its application as products in the fields of electronics, communication, military industry, etc., and is an important guarantee for the safe and stable operation of products. Summary of the Invention

[0006] Aiming at the deficiencies existing in the above-mentioned prior art, the present invention provides a conductive and corrosion-resistant coating on the surface of a magnesium alloy, a preparation method, and a modified magnesium alloy to solve the problem that the treatment processes of the existing surface protection coatings for magnesium alloy cannot have both anti-corrosion and conductive functions at the same time.

[0007] The first aspect of the present invention provides a method for preparing a conductive and corrosion-resistant coating on the surface of a magnesium alloy, comprising:

[0008] S1. Alkaline cleaning: Place the workpiece in a degreasing solution for 1 - 10 minutes, take out the workpiece and transfer it to room-temperature water for a water bath for 1 - 5 minutes, wherein the workpiece is made of magnesium alloy material;

[0009] S2. Acid pickling: Place the workpiece treated by alkaline cleaning in an acid pickling solution at room temperature for 100 - 130 seconds, and then wash the workpiece twice with water;

[0010] S3. Preparing the bottom layer coating: Place the workpiece treated by acid pickling in a mixed electrolytic solution, use a stainless steel plate as the cathode and the workpiece as the anode, and perform micro-arc oxidation treatment in a constant voltage working mode to obtain a bottom layer coating on the surface of the workpiece, wherein the bottom layer coating is a low-porosity MAO coating with a thickness of 20 - 35 μm;

[0011] S4. Washing and drying: Wash the workpiece after micro-arc oxidation treatment with water, and then dry it in an oven at 80 °C for 20 minutes;

[0012] S5. Preparing the intermediate layer coating: Stir the sealing solution for 30 minutes, then place the washed micro-arc oxidation workpiece in the sealing solution, keep it at -0.1 to -0.06 Mpa negative pressure for 1 - 3 hours, and then keep it at standard atmospheric pressure for 1 hour. Repeat this negative pressure process three times to obtain the intermediate layer coating, wherein the intermediate layer coating is a conductive nanoparticle layer;

[0013] S6. Drying: Dry the workpiece treated in step S5 at room temperature for 2 hours;

[0014] S7. Preparing the top layer coating: Place the workpiece treated in step S6 in an autoclave, with a deposition solution inside the autoclave, and use a gas-phase hydrothermal deposition process to obtain a top layer coating on the workpiece treated under negative pressure, wherein the top layer coating is a zinc aluminum oxide conductive layer with a thickness of 13 - 15 μm.

[0015] Preferably, the magnesium alloy material is an AZ series / ZK series / WE series magnesium alloy.

[0016] Preferably, the temperature of the degreasing solution is 60 - 70 °C. In addition, the composition of the degreasing solution is: sodium hydroxide 1 - 10 g / L, sodium carbonate 2 - 10 g / L, trisodium phosphate 1 - 10 g / L, sodium silicate 1 - 10 g / L, and sodium dodecyl sulfonate 0.01 - 0.05 g / L.

[0017] Preferably, the composition of the acid pickling solution is: boric acid 15 - 20 g / L, phosphoric acid 5 - 10 ml / L, ammonium bifluoride 2 - 10 g / L, and potassium sodium tartrate 1 - 4 g / L.

[0018] Preferably, the constant voltage working mode is as follows: the duty cycle is 20-40%, the frequency is 400-800 Hz, the working voltage is 360-420 V, and the oxidation time is 8-20 min;

[0019] In addition, the composition of the mixed electrolytic solution is: sodium silicate nonahydrate 6-20 g / L, potassium hydroxide 1-10 g / L, potassium fluozirconate 1-10 g / L, glycerol 1-10 ml / L, conductive mica 0.4-2 g / L, and conductive carbon black 0.3-3 g / L. The pH of the mixed electrolyte is 11.8-12.4.

[0020] Preferably, the composition of the sealing solution is: indium antimonide oxide nanoparticles 1.2-2.3 g / L, zinc aluminum oxide nanoparticles 1.1-2.8 g / L, Mxene nanosheets 0.8-1.3 g / L, and oes-70 surfactant 0.02-0.05 g / L.

[0021] Preferably, in step S7 when preparing the top layer coating, the workpiece is placed on the tray in the autoclave and does not directly contact the deposition solution. The filling rate of the deposition solution in the autoclave is 30-40%; the gas-phase hydrothermal deposition process is as follows: the autoclave is kept at 220 °C for 8-12 h. After cooling to room temperature, the workpiece is washed with water and then dried in an oven at 80 °C for 20 min.

[0022] Preferably, the composition of the deposition solution is: zinc acetate 2-5 g / L, aluminum nitrate 1-2 g / L, urea 0.3-1.5 g / L, sodium citrate 0.2-3 g / L, polypropylene alcohol 1.2-1.5 g / L, and polyethyleneimine 0.2-0.5 g / L.

[0023] In the second aspect of the present invention, there is provided a conductive and corrosion-resistant coating on the surface of a magnesium alloy, which is prepared by using a preparation method of a conductive and corrosion-resistant coating on the surface of a magnesium alloy. The conductive and corrosion-resistant coating includes a three-layer structure, and the total coating thickness is 33-50 μm. Among them, the bottom layer coating is a low-porosity MAO coating prepared by the micro-arc oxidation method, with a thickness of 20-35 μm; the middle layer coating is a conductive nanoparticle layer prepared by the negative pressure method; the top layer coating is a zinc aluminum oxide conductive layer prepared by the gas-phase deposition method, with a thickness of 13-15 μm.

[0024] In the third aspect of the present invention, there is provided a modified magnesium alloy, the surface of which has a conductive and corrosion-resistant coating prepared by using a preparation method of a conductive and corrosion-resistant coating on the surface of a magnesium alloy. The self-corrosion current density of this modified magnesium alloy is 0.18 - 1.8×10 - 7 A / cm 2 and the volume resistivity is 1.30 - 5.21×10 4 Ω·m.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention removes oil stains, dirt, sweat, etc. and the oxide layer from the magnesium alloy workpiece through degreasing and pickling, obtaining a clean and grease-free surface, which not only lays a foundation for obtaining a high-quality chemical conversion film, but also helps to improve the bonding strength between the subsequent micro-arc oxidation coating and the magnesium alloy substrate.

[0027] 2. The present invention combines the micro-arc oxidation process with a mixed electrolytic solution composed of sodium silicate nonahydrate, potassium hydroxide, potassium fluozirconate, glycerol, conductive mica and conductive carbon black to prepare a bottom layer coating on the magnesium alloy. It not only prepares a base layer with high bonding strength and excellent corrosion resistance, but also lays a solid foundation for further improving the bonding strength between the deposited layer and the magnesium alloy substrate.

[0028] 3. The present invention uses a sealing solution composed of indium antimonide oxide nanoparticles, aluminum zinc oxide nanoparticles, Mxene nanosheets and oes-70 surfactant to prepare an intermediate layer coating. It not only effectively seals the pores of the micro-arc oxidation coating, improves the durability of the coating, but also enhances the conductivity of the coating, providing an anchoring site for the subsequent deposited layer.

[0029] 4. The present invention combines the gas-phase hydrothermal deposition technology with a deposition solution composed of zinc acetate, aluminum nitrate, urea, sodium citrate, polypropylene alcohol and polyethyleneimine to prepare a dense aluminum zinc oxide coating on the magnesium alloy intermediate layer coating. It not only performs secondary sealing on the micropores of the micro-arc oxidation coating, but also further improves the conductivity of the coating.

[0030] 5. The present invention adopts the gas-phase hydrothermal deposition technology, which accelerates the diffusion of the reaction medium through a high-pressure environment, thereby greatly enhancing the reaction rate and effectively shortening the preparation time. At the same time, during this process, water vapor serves as the main reaction medium, and its excellent permeability promotes the uniform deposition of the conductive coating on the porous substrate, and the easily activated O-H bonds also effectively accelerate the reaction process. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0032] Figure 1 It is a schematic structural diagram of the conductive and corrosion-resistant coating on the magnesium alloy surface in the embodiment of the present invention;

[0033] Figure 2 It is a microscopic morphology diagram of the bottom layer coating in Embodiment 2 of the present invention;

[0034] Figure 3 This is the electrochemical test curve graph in Embodiment 3 of the present invention;

[0035] Figure 4 This is the failure graph of the preparation of the bottom layer coating in Comparative Example 1 of the present invention. Specific Embodiments

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] The first aspect of the present invention provides a method for preparing a conductive and corrosion-resistant coating on the surface of a magnesium alloy, including:

[0038] S1. Alkaline cleaning: Place the workpiece in a degreasing solution for 1 - 10 minutes, take out the workpiece and transfer it to water at room temperature for a water bath for 1 - 5 minutes, where the workpiece is made of magnesium alloy material.

[0039] Preferably, the magnesium alloy material is an AZ series / ZK series / WE series magnesium alloy.

[0040] Preferably, the temperature of the degreasing solution is 60 - 70 °C. In addition, the composition of the degreasing solution is: sodium hydroxide 1 - 10 g / L, sodium carbonate 2 - 10 g / L, trisodium phosphate 1 - 10 g / L, sodium silicate 1 - 10 g / L, and sodium dodecyl sulfonate 0.01 - 0.05 g / L.

[0041] S2. Acid pickling: Place the workpiece treated by alkaline cleaning in an acid pickling solution at room temperature for 100 - 130 seconds, and then wash the workpiece twice with water.

[0042] Preferably, the composition of the acid pickling solution is: boric acid 15 - 20 g / L, phosphoric acid 5 - 10 ml / L, ammonium bifluoride 2 - 10 g / L, and potassium sodium tartrate 1 - 4 g / L.

[0043] In this application, through degreasing and acid pickling, the oil stains, dirt, sweat, etc., and the oxide layer on the magnesium alloy workpiece are removed, and a clean and grease-free surface is obtained, which not only lays a foundation for obtaining a high-quality chemical conversion film, but also helps to improve the bonding strength between the subsequent micro-arc oxidation coating and the magnesium alloy substrate.

[0044] S3. Prepare the bottom layer coating: Place the workpiece treated by acid pickling in a mixed electrolytic solution, use a stainless steel plate as the cathode and the workpiece as the anode, and perform micro-arc oxidation treatment in a constant voltage working mode to obtain a bottom layer coating on the surface of the workpiece, where the bottom layer coating is a low-porosity MAO coating with a thickness of 20 - 35 μm.

[0045] Preferably, the constant voltage working mode is as follows: the duty cycle is 20-40%, the frequency is 400-800 Hz, the working voltage is 360-420 V, and the oxidation time is 8-20 min.

[0046] Preferably, the composition of the mixed electrolytic solution is: sodium silicate nonahydrate 6-20 g / L, potassium hydroxide 1-10 g / L, potassium fluozirconate 1-10 g / L, glycerol 1-10 ml / L, conductive mica 0.4-2 g / L, and conductive carbon black 0.3-3 g / L, and the pH of the mixed electrolyte is 11.8-12.4.

[0047] It should be noted that in this application, sodium silicate nonahydrate is used to provide SiO3 2- , to form a silicate coating; potassium hydroxide is used to adjust the pH of the electrolyte to 11.8-12.4; potassium fluozirconate promotes discharge and can generate ZrO2 components during micro-arc oxidation, which can not only improve the wear resistance of the coating, but also refine the pores of the coating; glycerol is used to inhibit spark discharge and improve the coating uniformity; conductive mica and conductive carbon black are used to improve the conductivity of the micro-arc oxidation layer and reduce the porosity of the coating. During micro-arc oxidation, the molten material is ejected from the discharge channel and rapidly solidifies to form pores, which provide channels for corrosive media. Therefore, the addition of conductive mica, conductive carbon black, and potassium fluozirconate in this application effectively enhances the corrosion resistance of the coating.

[0048] In this application, a base layer with high bonding strength and excellent corrosion resistance is prepared by the micro-arc oxidation process, laying a solid foundation for further improving the bonding strength between the deposition layer and the magnesium alloy substrate.

[0049] S4. Water washing and drying: Wash the workpiece after micro-arc oxidation treatment with water, and then dry it in an oven at 80°C for 20 min.

[0050] S5. Prepare the intermediate layer coating: Stir the sealing solution for 30 min, then place the water-washed micro-arc oxidation workpiece in the sealing solution, keep it at a negative pressure of -0.1 to -0.06 Mpa for 1 to 3 h, and then keep it at standard atmospheric pressure for 1 h. Repeat this negative pressure process three times to obtain the intermediate layer coating, where the intermediate layer coating is a conductive nanoparticle layer.

[0051] It should be noted that in the embodiments of this application, "this negative pressure process" refers to keeping it at a negative pressure of -0.1 to -0.06 Mpa for 1 to 3 h, and then keeping it at standard atmospheric pressure for 1 h.

[0052] Preferably, the composition of the hole-sealing liquid is as follows: 1.2 - 2.3 g / L of indium antimonide oxide nanoparticles, 1.1 - 2.8 g / L of aluminum zinc oxide nanoparticles, 0.8 - 1.3 g / L of Mxene nanosheets, and 0.02 - 0.05 g / L of oes-70 surfactant.

[0053] It should be noted that indium antimonide oxide nanoparticles, aluminum zinc oxide nanoparticles, and Mxene nanosheets all have good electrical conductivity. They can not only be used to block the pores of the micro-arc oxidation coating to improve the durability of the coating, but also enhance the electrical conductivity of the coating, providing binding sites for the next step of depositing an aluminum zinc oxide conductive layer to enhance the binding force. As a surfactant, oes-70 can prevent the sedimentation of nanomaterials in the hole-sealing liquid. Therefore, in this application, the hole-sealing liquid composed of indium antimonide oxide nanoparticles, aluminum zinc oxide nanoparticles, Mxene nanosheets, and oes-70 surfactant is used to prepare the intermediate layer coating, which not only effectively blocks the pores of the micro-arc oxidation coating, improves the durability of the coating, but also enhances the electrical conductivity of the coating, providing anchor sites for the subsequent deposited layer.

[0054] S6. Drying: Dry the workpiece treated in step S5 at room temperature for 2 h.

[0055] S7. Preparing the top layer coating: Place the workpiece treated in step S6 in an autoclave. The autoclave contains a deposition solution. Use the gas-phase hydrothermal deposition process to prepare the top layer coating on the workpiece that has undergone negative pressure treatment. The top layer coating is an aluminum zinc oxide conductive layer with a thickness of 13 - 15 μm.

[0056] Preferably, when preparing the top layer coating in step S7, the workpiece is placed on the tray in the autoclave and does not come into direct contact with the deposition solution. The filling rate of the deposition solution in the autoclave is 30 - 40%; the gas-phase hydrothermal deposition process is as follows: The autoclave is kept at 220°C for 8 - 12 h. After cooling to room temperature, the workpiece is washed with water and then dried in an oven at 80°C for 20 min.

[0057] In addition, in the embodiments of this application, a number of round holes are equidistantly arranged at the bottom of the tray, and a number of card slots are equidistantly arranged on the tray. One workpiece is placed in each card slot. With such a design, when preparing the top layer coating for multiple workpieces at one time, the water vapor generated by the deposition solution can contact each workpiece more smoothly and fully, thereby making the preparation effect of the top layer coating of many workpieces better.

[0058] Preferably, the composition of the deposition solution is as follows: 2 - 5 g / L of zinc acetate, 1 - 2 g / L of aluminum nitrate, 0.3 - 1.5 g / L of urea, 0.2 - 3 g / L of sodium citrate, 1.2 - 1.5 g / L of polypropylene alcohol, and 0.2 - 0.5 g / L of polyethyleneimine.

[0059] It should be noted that zinc acetate is used to provide zinc ions to make the film layer thickness uniform; sodium citrate is used as a chelating agent, which can form a complex with a cyclic structure with metal ions to inhibit the rapid hydrolysis of metal ions and make the prepared film layer denser; urea decomposes under high temperature and high pressure to provide an alkaline environment for the preparation of aluminum zinc oxide; polypropylene alcohol and polyethyleneimine can be used to adjust the morphology of aluminum zinc oxide. The present invention uses vapor-phase hydrothermal deposition to prepare a dense aluminum zinc oxide coating, which not only plugs the micropores of the micro-arc oxidation coating a second time, but also further improves the conductivity of the coating.

[0060] In addition, magnesium alloys are easily corroded by water in a high-temperature environment. The present invention uses vapor-phase hydrothermal deposition technology to convert liquid water into gaseous water, which not only avoids the direct contact between magnesium alloys and water in a high-temperature environment, but also weakens the corrosion effect of liquid water on magnesium alloys through gaseous water.

[0061] It should be noted that in this application, when the variables in steps S3 and S7 exceed the value range, the coating prepared in this step will fail; when the variables in steps S1, S2 and S5 exceed the value range, the treatment effect in this step will become worse.

[0062] As Figure 1 shown, the second aspect of the present invention provides a conductive and corrosion-resistant coating on the surface of a magnesium alloy, which is prepared by a method for preparing a conductive and corrosion-resistant coating on the surface of a magnesium alloy. The conductive and corrosion-resistant coating includes a three-layer structure, and the total coating thickness is 33-50 μm. The bottom layer coating is a low-porosity MAO coating prepared by the micro-arc oxidation method, with a thickness of 20-35 μm; the middle layer coating is a conductive nanoparticle layer prepared by a negative pressure method; the top layer coating is a zinc aluminum oxide conductive layer prepared by a vapor deposition method, with a thickness of 13-15 μm.

[0063] It should be noted that since the thickness of the middle layer coating is extremely small, the total coating thickness in this application = the thickness of the bottom layer coating + the thickness of the top layer coating.

[0064] The third aspect of the present invention provides a modified magnesium alloy, the surface of which has a conductive and corrosion-resistant coating prepared by a method for preparing a conductive and corrosion-resistant coating on the surface of a magnesium alloy. The self-corrosion current density of this modified magnesium alloy is 0.18 - 1.8×10 - 7 A / cm 2 , and the volume resistivity is 1.30 - 5.21×10 4 Ω·m.

[0065] Based on the foregoing conductive and corrosion-resistant coating on the surface of a magnesium alloy and its preparation method, the present invention also conducted the following multiple groups of experiments.

[0066] It should be noted that all the raw materials used in the following experiments are commercially available raw materials.

[0067] Example 1

[0068] A conductive and corrosion-resistant coating on the surface of a magnesium alloy. The coating comprises a three-layer structure. The bottom layer coating is a low-porosity MAO coating prepared by micro-arc oxidation method, with a thickness of 20 μm; the middle layer is a conductive nanoparticle layer prepared by a negative pressure method; the top layer is a zinc aluminum oxide conductive layer prepared by chemical vapor deposition method, with a thickness of 15 μm. The preparation steps of the conductive and corrosion-resistant coating on the surface of the magnesium alloy are as follows:

[0069] S1. Alkaline cleaning: Place the workpiece in a degreasing solution at 60 °C for 5 min, then take out the workpiece and transfer it to water at room temperature for a 3-min water bath. The workpiece is made of AZ31 magnesium alloy material; the composition of the degreasing solution is: 1 g / L of sodium hydroxide, 9 g / L of sodium carbonate, 10 g / L of trisodium phosphate, 1 g / L of sodium silicate, and 0.05 g / L of sodium dodecyl sulfonate.

[0070] S2. Acid pickling: Place the workpiece after alkaline cleaning in an acid pickling solution at room temperature for 130 s, then wash the workpiece twice with water. The composition of the acid pickling solution is: 20 g / L of boric acid, 6 ml / L of phosphoric acid, 2 g / L of ammonium bifluoride, and 3 g / L of potassium sodium tartrate.

[0071] S3. Preparation of the bottom layer coating: Place the workpiece after acid pickling in a mixed electrolytic solution, using a stainless steel plate as the cathode and the workpiece as the anode, and carry out micro-arc oxidation treatment in a constant voltage working mode to obtain the bottom layer coating on the surface of the workpiece. The constant voltage working mode is: duty cycle 40%, frequency 480 Hz, working voltage 420 V, oxidation time 20 min; the composition of the mixed electrolytic solution is: 18 g / L of sodium silicate nonahydrate, 9 g / L of potassium hydroxide, 8 g / L of potassium fluozirconate, 8 ml / L of glycerol, 1.8 g / L of conductive mica, and 2.8 g / L of conductive carbon black; the pH of the mixed electrolyte is 11.8.

[0072] S4. Water washing and drying: Wash the workpiece after micro-arc oxidation treatment with water, and then dry it in an oven at 80 °C for 20 min.

[0073] S5. Preparation of the middle layer coating: Stir the sealing solution for 30 min, then place the water-washed micro-arc oxidation workpiece in the sealing solution, keep it at -0.1 Mpa negative pressure for 1.8 h, then place it under standard atmospheric pressure for 1 h, and repeat this negative pressure process three times to obtain the middle layer coating. The composition of the sealing solution is: 2.1 g / L of indium antimonide oxide nanoparticles, 2.6 g / L of zinc aluminum oxide nanoparticles, 1.2 g / L of Mxene nanosheets, and 0.04 g / L of oes-70 surfactant.

[0074] S6. Drying: Dry the workpiece after step S5 treatment at room temperature for 2 h.

[0075] S7. Preparation of the top layer coating: Place the workpiece after being processed in step S6 in the card slot on the tray in the autoclave. The deposition solution is placed inside the autoclave, and the filling rate of the deposition solution in the autoclave is 33%. Use the gas-phase hydrothermal deposition process to prepare the top layer coating on the workpiece that has undergone negative pressure treatment. The gas-phase hydrothermal deposition process is as follows: The autoclave is kept at 220 °C for 8.5 h. After cooling to room temperature, wash the workpiece with water and then dry it in an oven at 80 °C for 20 min. The composition of the deposition solution is: zinc acetate 4 g / L, aluminum nitrate 2 g / L, urea 1.4 g / L, sodium citrate 0.2 g / L, polypropylene alcohol 1.4 g / L, and polyethyleneimine 0.4 g / L.

[0076] Example 2

[0077] A conductive and corrosion-resistant coating on the surface of a magnesium alloy. This coating includes a three-layer structure. The bottom layer coating is a low-porosity MAO coating prepared by the micro-arc oxidation method, with a thickness of 25 μm, as Figure 2 shown; the middle layer is a conductive nanoparticle layer prepared by the negative pressure method; the top layer is a zinc oxide-aluminum conductive layer prepared by the gas-phase deposition method, with a thickness of 14 μm. The preparation steps of the conductive and corrosion-resistant coating on the surface of this magnesium alloy are as follows:

[0078] S1. Alkaline cleaning: Place the workpiece in the degreasing solution at 65 °C for 1 min, then take out the workpiece and transfer it to water at room temperature for a water bath for 2 min. The workpiece is made of ZK60 magnesium alloy material. The composition of the degreasing solution is: sodium hydroxide 10 g / L, sodium carbonate 2 g / L, trisodium phosphate 9 g / L, sodium silicate 5 g / L, and sodium dodecyl sulfonate 0.04 g / L.

[0079] S2. Acid cleaning: Place the workpiece after alkaline cleaning treatment in the acid cleaning solution at room temperature for 100 s, then wash the workpiece twice with water. The composition of the acid cleaning solution is: boric acid 18 g / L, phosphoric acid 10 ml / L, ammonium bifluoride 5 g / L, and potassium sodium tartrate 4 g / L.

[0080] S3. Preparation of the bottom layer coating: Place the workpiece after acid cleaning treatment in the mixed electrolytic solution, use the stainless steel plate as the cathode and the workpiece as the anode, and carry out micro-arc oxidation treatment in the constant voltage working mode to obtain the bottom layer coating on the surface of the workpiece. The constant voltage working mode is: duty cycle 30%, frequency 400 Hz, working voltage 380 V, oxidation time 17 min. The composition of the mixed electrolytic solution is: sodium silicate nonahydrate 16 g / L, potassium hydroxide 8 g / L, potassium fluozirconate 10 g / L, glycerol 10 ml / L, conductive mica 0.4 g / L, and conductive carbon black 3 g / L; the pH of the mixed electrolytic solution is 12.0.

[0081] In this application, the microscopic morphology diagram of the bottom layer coating in Example 2 is as Figure 2 shown, from Figure 2It can be clearly seen that there are many micropores on the MAO coating, which can provide attachment sites for the intermediate layer coating - the conductive nanoparticle layer and are also conducive to providing anchor sites for the zinc aluminum oxide deposition layer.

[0082] S4. Water washing and drying: The workpiece after micro-arc oxidation treatment is washed with water and then dried in an oven at 80 °C for 20 min.

[0083] S5. Preparation of the intermediate layer coating: The sealing solution is stirred for 30 min, and then the micro-arc oxidized workpiece after water washing is placed in the sealing solution, maintained at -0.06 Mpa negative pressure for 1.5 h, and then maintained at standard atmospheric pressure for 1 h. This negative pressure process is repeated three times to obtain the intermediate layer coating. The composition of the sealing solution is: indium antimonide oxide nanoparticles 1.8 g / L, zinc aluminum oxide nanoparticles 2.4 g / L, Mxene nanosheets 1.1 g / L, and oes-70 surfactant 0.03 g / L.

[0084] S6. Drying: The workpiece after being treated in step S5 is dried at room temperature for 2 h.

[0085] S7. Preparation of the top layer coating: The workpiece after being treated in step S6 is placed in the card slot on the tray in the autoclave. The deposition solution is placed inside the autoclave, and the filling rate of the deposition solution in the autoclave is 38%. The top layer coating is prepared on the workpiece after negative pressure treatment by the gas-phase hydrothermal deposition process. The gas-phase hydrothermal deposition process is as follows: The autoclave is kept at 220 °C for 8 h, cooled to room temperature, the workpiece is washed with water and then dried in an oven at 80 °C for 20 min; the composition of the deposition solution is: zinc acetate 5 g / L, aluminum nitrate 1.5 g / L, urea 1.5 g / L, sodium citrate 3 g / L, polypropylene alcohol 1.5 g / L, and polyethyleneimine 0.3 g / L.

[0086] Example 3

[0087] A conductive and corrosion-resistant coating on the surface of a magnesium alloy. The coating includes a three-layer structure. The bottom layer coating is a low-porosity MAO coating prepared by the micro-arc oxidation method, with a thickness of 35 μm; the intermediate layer is a conductive nanoparticle layer prepared by the negative pressure method; the top layer is a zinc aluminum oxide conductive layer prepared by the vapor deposition method, with a thickness of 13 μm. The preparation steps of the conductive and corrosion-resistant coating on the surface of the magnesium alloy are as follows:

[0088] S1. Alkaline washing: The workpiece is placed in a degreasing solution at 70 °C for 10 min, then the workpiece is taken out and transferred to water at room temperature for a 1-min water bath. The workpiece is made of ZK61 magnesium alloy material; the composition of the degreasing solution is: sodium hydroxide 7 g / L, sodium carbonate 6 g / L, trisodium phosphate 7 g / L, sodium silicate 6 g / L, and sodium dodecyl sulfonate 0.01 g / L.

[0089] S2. Pickling: Place the workpiece that has undergone alkali washing treatment in the pickling solution and treat it at room temperature for 120 s, then wash the workpiece twice. The composition of the pickling solution is: boric acid 17 g / L, phosphoric acid 9 ml / L, ammonium bifluoride 7 g / L, and sodium potassium tartrate 1 g / L.

[0090] S3. Prepare the bottom layer coating: Place the workpiece that has undergone pickling treatment in the mixed electrolytic solution, use a stainless steel plate as the cathode and the workpiece as the anode, and perform micro-arc oxidation treatment in the constant voltage working mode. Then, a bottom layer coating is obtained on the surface of the workpiece. The constant voltage working mode is as follows: duty cycle 40%, frequency 600 Hz, working voltage 380 V, oxidation time 17 min; the composition of the mixed electrolytic solution is: sodium silicate nonahydrate 6 g / L, potassium hydroxide 4 g / L, potassium fluozirconate 1 g / L, glycerol 4 ml / L, conductive mica 0.8 g / L, and conductive carbon black 0.6 g / L; the pH of the mixed electrolyte is 12.4.

[0091] S4. Wash and dry: Wash the workpiece that has undergone micro-arc oxidation treatment, and then dry it in an oven at 80 °C for 20 min after washing.

[0092] S5. Prepare the intermediate layer coating: Stir the sealing solution for 30 min, then place the washed micro-arc oxidation workpiece in the sealing solution, keep it under a negative pressure of -0.08 Mpa for 2 h, and then keep it under standard atmospheric pressure for 1 h. Repeat this negative pressure process three times to obtain the intermediate layer coating. The composition of the sealing solution is: indium antimonide oxide nanoparticles 1.2 g / L, zinc aluminum oxide nanoparticles 1.1 g / L, Mxene nanosheets 0.8 g / L, and oes-70 surfactant 0.02 g / L.

[0093] S6. Dry: Dry the workpiece treated in step S5 at room temperature for 2 h.

[0094] S7. Prepare the top layer coating: Place the workpiece treated in step S6 in the card slot on the tray in the autoclave. The deposition solution is placed inside the autoclave, and the filling rate of the deposition solution in the autoclave is 35%. Use the gas-phase hydrothermal deposition process to obtain the top layer coating on the workpiece that has undergone negative pressure treatment. The gas-phase hydrothermal deposition process is as follows: keep the autoclave at 220 °C for 10 h, after cooling to room temperature, wash the workpiece and then dry it in an oven at 80 °C for 20 min; the composition of the deposition solution is: zinc acetate 2 g / L, aluminum nitrate 1 g / L, urea 0.3 g / L, sodium citrate 0.4 g / L, polypropylene alcohol 1.2 g / L, and polyethyleneimine 0.5 g / L.

[0095] In this application, the modified magnesium alloy with a conductive and corrosion-resistant coating prepared according to Example 3 on its surface has an electrochemical test curve as Figure 3 shown, and Figure 3 it can be known from this the self-corrosion current density of the modified magnesium alloy.

[0096] Example 4

[0097] A conductive and corrosion-resistant coating on the surface of a magnesium alloy. The coating includes a three-layer structure. The bottom layer is a low-porosity MAO coating prepared by micro-arc oxidation, with a thickness of 35 μm. The middle layer is a conductive nanoparticle layer prepared by a negative pressure method. The top layer is a zinc aluminum oxide conductive layer prepared by chemical vapor deposition, with a thickness of 15 μm. The preparation steps of the conductive and corrosion-resistant coating on the surface of the magnesium alloy are as follows:

[0098] S1. Alkaline cleaning: Place the workpiece in a degreasing solution at 60 °C for 10 min, then take out the workpiece and transfer it to water at room temperature for a 5-min water bath. The workpiece is made of WE43 magnesium alloy material. The composition of the degreasing solution is: sodium hydroxide 4 g / L, sodium carbonate 10 g / L, trisodium phosphate 3 g / L, sodium silicate 8 g / L, and sodium dodecyl sulfonate 0.02 g / L.

[0099] S2. Acid pickling: Place the workpiece after alkaline cleaning in an acid pickling solution at room temperature for 110 s, and then wash the workpiece twice with water. The composition of the acid pickling solution is: boric acid 16 g / L, phosphoric acid 7 ml / L, ammonium bifluoride 10 g / L, and potassium sodium tartrate 3 g / L.

[0100] S3. Preparation of the bottom layer coating: Place the workpiece after acid pickling in a mixed electrolytic solution, with a stainless steel plate as the cathode and the workpiece as the anode, and perform micro-arc oxidation treatment in a constant voltage working mode to obtain the bottom layer coating on the surface of the workpiece. The constant voltage working mode is: duty cycle 35%, frequency 800 Hz, working voltage 360 V, oxidation time 12 min. The composition of the mixed electrolytic solution is: sodium silicate nonahydrate 20 g / L, potassium hydroxide 10 g / L, potassium fluozirconate 6 g / L, glycerol 1 ml / L, conductive mica 0.6 g / L, and conductive carbon black 0.3 g / L. The pH of the mixed electrolyte is 12.2.

[0101] S4. Water washing and drying: Wash the workpiece after micro-arc oxidation treatment with water, and then dry it in an oven at 80 °C for 20 min.

[0102] S5. Preparation of the middle layer coating: Stir the sealing solution for 30 min, then place the water-washed micro-arc oxidation workpiece in the sealing solution, keep it at -0.1 Mpa negative pressure for 3 h, then place it under standard atmospheric pressure for 1 h, and repeat this negative pressure process three times to obtain the middle layer coating. The composition of the sealing solution is: indium antimonide oxide nanoparticles 1.4 g / L, zinc aluminum oxide nanoparticles 1.3 g / L, Mxene nanosheets 1 g / L, and oes-70 surfactant 0.04 g / L.

[0103] S6. Drying: Dry the workpiece after being treated in step S5 at room temperature for 2 h.

[0104] S7. Preparation of the top layer coating: Place the workpiece after being treated in step S6 in the card slot on the tray in the autoclave. The autoclave is internally provided with a deposition solution, and the filling rate of the deposition solution in the autoclave is 30%. A top layer coating is prepared on the workpiece after negative pressure treatment by means of gas-phase hydrothermal deposition process. The gas-phase hydrothermal deposition process is as follows: The autoclave is kept at 220 °C for 12 h. After cooling to room temperature, the workpiece is washed with water and then dried in an oven at 80 °C for 20 min; The composition of the deposition solution is: zinc acetate 4 g / L, aluminum nitrate 2 g / L, urea 1.4 g / L, sodium citrate 0.2 g / L, polypropylene alcohol 1.4 g / L and polyethyleneimine 0.4 g / L.

[0105] Example 5

[0106] A conductive and corrosion-resistant coating on the surface of a magnesium alloy. The coating includes a three-layer structure. The bottom layer coating is a low-porosity MAO coating prepared by micro-arc oxidation method, with a thickness of 20 μm; The intermediate layer is a conductive nanoparticle layer prepared by a negative pressure method; The top layer is a zinc oxide-aluminum conductive layer prepared by a gas-phase deposition method, with a thickness of 13 μm. The preparation steps of the conductive and corrosion-resistant coating on the surface of the magnesium alloy are as follows:

[0107] S1. Alkaline washing: Place the workpiece in a degreasing solution at 68 °C for 7 min, then take out the workpiece and transfer it to water at room temperature for a 4-min water bath. The workpiece is made of AZ91 magnesium alloy material; The composition of the degreasing solution is: sodium hydroxide 3 g / L, sodium carbonate 8 g / L, trisodium phosphate 1 g / L, sodium silicate 10 g / L and sodium dodecyl sulfonate 0.03 g / L.

[0108] S2. Acid washing: Place the workpiece after alkaline washing treatment in an acid washing solution and treat it at room temperature for 100 s, then wash the workpiece twice with water. The composition of the acid washing solution is: boric acid 15 g / L, phosphoric acid 5 ml / L, ammonium bifluoride 9 g / L and potassium sodium tartrate 3 g / L.

[0109] S3. Preparation of the bottom layer coating: Place the workpiece after acid washing treatment in a mixed electrolytic solution, use a stainless steel plate as the cathode and the workpiece as the anode, and carry out micro-arc oxidation treatment in a constant voltage working mode. Then a bottom layer coating is obtained on the surface of the workpiece. The constant voltage working mode is as follows: duty cycle 20%, frequency 560 Hz, working voltage 400 V, oxidation time 8 min; The composition of the mixed electrolytic solution is: sodium silicate nonahydrate 14 g / L, potassium hydroxide 1 g / L, potassium fluozirconate 2 g / L, glycerol 9 ml / L, conductive mica 2 g / L and conductive carbon black 2.4 g / L; The pH of the mixed electrolyte is 12.1.

[0110] S4. Washing and drying: Wash the workpiece after micro-arc oxidation treatment with water, and then dry it in an oven at 80 °C for 20 min.

[0111] S5. Preparation of the intermediate layer coating: Stir the sealing solution for 30 min, then place the micro-arc oxidation workpiece after water washing into the sealing solution, keep it under a negative pressure of -0.07 Mpa for 1 h, and then keep it under standard atmospheric pressure for 1 h. Repeat this negative pressure process three times to obtain the intermediate layer coating. The composition of the sealing solution is: indium antimonide oxide nanoparticles 2.3 g / L, aluminum zinc oxide nanoparticles 2.8 g / L, Mxene nanosheets 1.3 g / L, and oes-70 surfactant 0.05 g / L.

[0112] S6. Drying: Dry the workpiece treated in step S5 at room temperature for 2 h.

[0113] S7. Preparation of the top layer coating: Place the workpiece treated in step S6 into the card slot on the tray in the autoclave. The deposition solution is placed inside the autoclave, and the filling rate of the deposition solution in the autoclave is 40%. Use the gas-phase hydrothermal deposition process to obtain the top layer coating on the workpiece after negative pressure treatment. The gas-phase hydrothermal deposition process is as follows: Keep the autoclave at 220 °C for 9 h. After cooling to room temperature, wash the workpiece with water and then dry it in an oven at 80 °C for 20 min. The composition of the deposition solution is: zinc acetate 3 g / L, aluminum nitrate 1.4 g / L, urea 0.8 g / L, sodium citrate 2.6 g / L, polypropylene alcohol 1.3 g / L, and polyethyleneimine 0.2 g / L.

[0114] Comparative Example 1

[0115] Different from Example 1, when preparing the bottom layer coating in step S3, the composition of the mixed electrolytic solution is: sodium silicate nonahydrate 18 g / L, Potassium hydroxide 0.5 g / L , potassium fluozirconate 8 g / L, glycerol 8 ml / L, conductive mica 1.8 g / L, and conductive carbon black 2.8 g / L.

[0116] As Figure 4 shown, during the experiment, in Comparative Example 1, due to the potassium hydroxide concentration exceeding the range, the pH value of the mixed electrolytic solution < 11.8, resulting in the protonation and dehydration of silicate ions in the electrolytic solution to form silica sol, which cannot stably form a continuous film layer, thus unable to prepare the bottom layer coating. In addition, a lower pH may also lead to abnormal electrochemical conditions, abnormal conductivity, and the failure of the micro-arc discharge stage during the film formation process.

[0117] Comparative Example 2

[0118] Different from Example 1, when preparing the top layer coating in step S7, the composition of the deposition solution is: zinc acetate 1 g / L, aluminum nitrate 2 g / L, urea 1.4 g / L, sodium citrate 0.2 g / L, polypropylene alcohol 1.4 g / L, and polyethyleneimine 0.4 g / L.

[0119] During the experiment, in Comparative Example 2, since the zinc acetate was below the specified range, the zinc ion component for core film formation in the deposition solution was too low, resulting in a decrease in the coating growth rate, and even the inability to form a continuous film layer. Eventually, the film layer was uneven in thickness, loose, and there was no deposition locally, causing the failure of the preparation of the conductive layer.

[0120] Performance test: The modified magnesium alloys with conductive and corrosion-resistant coatings prepared according to the methods described in Examples 1-5 and Comparative Examples 1-2 were subjected to performance tests, and the obtained test data are recorded in Table 1.

[0121] Table 1. Performance test results of modified magnesium alloys

[0122]

[0123] In this application, the smaller the self-corrosion current density of the modified magnesium alloy, the better its corrosion resistance; the larger the volume resistivity, the better its electrical conductivity. It can be clearly seen from Table 1 that three-layer coatings were prepared in Examples 1-5, which have excellent corrosion resistance and also exhibit excellent electrical conductivity. The corrosion resistance and electrical conductivity of Examples 1-5 are better than those of Comparative Examples 1 and 2. In Comparative Example 1, since the concentration of potassium hydroxide exceeded the range, it first led to the failure of the preparation of the bottom layer coating, and then the middle layer coating and the top layer coating could not be prepared either, having neither corrosion resistance nor electrical conductivity; while in Comparative Example 2, since the zinc acetate was below the specified range, the preparation of the conductive layer failed, the electrical conductivity was poor, and it did not have good corrosion resistance.

[0124] In summary, due to the key components in Comparative Examples 1-2 exceeding the specified range, there are significant defects in terms of corrosion resistance and electrical conductivity, further verifying the superiority of the technical solution of this application.

[0125] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a conductive and corrosion-resistant coating on the surface of a magnesium alloy, characterized in that, Including: S1. Alkaline cleaning: Place the workpiece in the degreasing solution for 1 - 10 min, take out the workpiece and transfer it to room-temperature water for water bath for 1 - 5 min, where the workpiece is made of magnesium alloy material; S2. Acid pickling: Place the workpiece after alkaline cleaning in the acid pickling solution for normal-temperature treatment for 100 - 130 s, and then wash the workpiece twice with water; S3. Prepare the bottom layer coating: Place the workpiece after acid pickling in the mixed electrolytic solution, use the stainless steel plate as the cathode and the workpiece as the anode, and carry out micro-arc oxidation treatment in the constant voltage working mode, and obtain the bottom layer coating on the surface of the workpiece, where the bottom layer coating is a low-porosity MAO coating with a thickness of 20 - 35 μm; S4. Wash and dry: Wash the workpiece after micro-arc oxidation treatment with water, and dry it in an oven at 80 °C for 20 min after washing; S5. Prepare the intermediate layer coating: Stir the sealing solution for 30 min, then place the washed micro-arc oxidation workpiece in the sealing solution, keep it under a negative pressure of -0.1 - -0.06 Mpa for 1 - 3 h, and then keep it under the standard atmospheric pressure for 1 h, repeat this negative pressure process three times to obtain the intermediate layer coating, where the intermediate layer coating is a conductive nano-particle layer; S6. Dry: Dry the workpiece after being treated in step S5 at room temperature for 2 h; S7. Prepare the top layer coating: Place the workpiece after being treated in step S6 in an autoclave, with the deposition solution inside the autoclave, and obtain the top layer coating on the workpiece after negative pressure treatment by using the gas-phase hydrothermal deposition process, where the top layer coating is a zinc oxide aluminum conductive layer with a thickness of 13 - 15 μm.

2. The preparation method of a conductive and corrosion-resistant coating on the surface of a magnesium alloy according to claim 1, characterized in that, The magnesium alloy material is AZ series / ZK series / WE series magnesium alloy.

3. The preparation method of a conductive and corrosion-resistant coating on the surface of a magnesium alloy according to claim 1, characterized in that, The temperature of the degreasing solution is 60 - 70 °C. In addition, the composition of the degreasing solution is: sodium hydroxide 1 - 10 g / L, sodium carbonate 2 - 10 g / L, trisodium phosphate 1 - 10 g / L, sodium silicate 1 - 10 g / L, and sodium dodecyl sulfonate 0.01 - 0.05 g / L.

4. The preparation method of a conductive and corrosion-resistant coating on the surface of a magnesium alloy according to claim 1, characterized in that, The composition of the acid pickling solution is: boric acid 15 - 20 g / L, phosphoric acid 5 - 10 ml / L, ammonium bifluoride 2 - 10 g / L, and potassium sodium tartrate 1 - 4 g / L.

5. The preparation method of a conductive and corrosion-resistant coating on the surface of a magnesium alloy according to claim 1, characterized in that, The constant voltage working mode is: duty cycle is 20 - 40%, frequency is 400 - 800 Hz, working voltage is 360 - 420 V, and oxidation time is 8 - 20 min; In addition, the composition of the mixed electrolytic solution is: sodium silicate nonahydrate 6 - 20 g / L, potassium hydroxide 1 - 10 g / L, potassium fluozirconate 1 - 10 g / L, glycerol 1 - 10 ml / L, conductive mica 0.4 - 2 g / L, and conductive carbon black 0.3 - 3 g / L, and the pH of the mixed electrolytic solution is 11.8 - 12.

4.

6. The preparation method of a conductive and corrosion-resistant coating on the surface of a magnesium alloy according to claim 1, wherein, The composition of the sealing solution is: indium antimonide oxide nanoparticles 1.2 - 2.3 g / L, zinc oxide aluminum nanoparticles 1.1 - 2.8 g / L, Mxene nanosheets 0.8 - 1.3 g / L, and oes-70 surfactant 0.02 - 0.05 g / L.

7. The preparation method of a conductive and corrosion-resistant coating on the surface of a magnesium alloy according to claim 1, wherein, In step S7, when preparing the top coating, the workpiece is placed on a tray in an autoclave without direct contact with the deposition solution. The filling rate of the deposition solution in the autoclave is 30-40%; the gas-phase hydrothermal deposition process is as follows: the autoclave is kept at 220°C for 8-12 h, and after cooling to room temperature, the workpiece is washed with water and then dried in an oven at 80°C for 20 min.

8. The preparation method of a conductive and corrosion-resistant coating on the surface of a magnesium alloy according to claim 1, characterized in that, The composition of the deposition solution is: zinc acetate 2-5 g / L, aluminum nitrate 1-2 g / L, urea 0.3-1.5 g / L, sodium citrate 0.2-3 g / L, polypropylene alcohol 1.2-1.5 g / L, and polyethyleneimine 0.2-0.5 g / L.

9. A conductive and corrosion-resistant coating on the surface of a magnesium alloy, which is prepared by using the preparation method of a conductive and corrosion-resistant coating on the surface of a magnesium alloy according to any one of claims 1-8, and is characterized in that, The conductive and corrosion-resistant coating includes a three-layer structure with a total coating thickness of 33-50 μm. Among them, the bottom layer coating is a low-porosity MAO coating prepared by micro-arc oxidation, with a thickness of 20-35 μm; the middle layer coating is a conductive nanoparticle layer prepared by a negative pressure method; the top layer coating is a zinc aluminum oxide conductive layer prepared by vapor deposition, with a thickness of 13-15 μm.

10. A modified magnesium alloy, with a conductive and corrosion-resistant coating prepared by the preparation method of a magnesium alloy surface conductive and corrosion-resistant coating according to any one of claims 1-8 or the conductive and corrosion-resistant coating according to claim 9 on its surface, characterized in that, The self-corrosion current density of the modified magnesium alloy is 0.18 - 1.8×10 -7 A / cm 2 , and the volume resistivity is 1.30 - 5.21×10 4 Ω·m.

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