Preparation method of medical magnesium alloy active anticorrosion coating with self-healing capability

Abstract

The application relates to a preparation method of a self-healing ability medical magnesium alloy active anticorrosion coating and belongs to the technical field of functional materials and magnesium alloy surface corrosion prevention. The method comprises the following steps: 1) magnesium alloy surface pretreatment, smoothing the magnesium alloy surface, and then ultrasonic cleaning; 2) laser processing treatment is conducted on the pretreated magnesium alloy, and the magnesium alloy is cleaned and dried after processing; 3) the magnesium alloy surface obtained through step 2) is subjected to a hydrothermal reaction, and the magnesium alloy is cleaned and dried after the reaction; and 4) the magnesium alloy surface obtained through step 3) is soaked in a MnCl2.4H2O solution, and the LTS / Mg-Mn coating is obtained after natural drying after the soaking is completed. The application has the advantages of simple preparation process, simple operation, high safety in the preparation process, effective reduction of energy consumption and pollution, non-need of using expensive production equipment, low production cost, high practical value, provision of a novel and effective method for preparing potential medical implant materials from magnesium alloy materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of functional materials and magnesium alloy surface corrosion prevention technology, and particularly relates to a preparation method of a self-healing active corrosion prevention coating for medical magnesium alloy. BACKGROUND

[0002] Hydrothermal treatment refers to an effective method for material processing in which a water solution is used as a reaction system, a relatively high-temperature and high-pressure reaction environment is created by heating and pressurizing the reaction system, and usually difficultly soluble or insoluble substances are dissolved and recrystallized. The coating prepared by hydrothermal treatment has the advantages of good dispersity and easy control of crystal form, and the hydrothermal method is the most commonly used processing method for preparing a magnesium alloy surface corrosion prevention coating.

[0003] As a new type of degradable medical metal implant material, magnesium alloy has become a research hotspot in the field of biomaterials and is increasingly concerned and valued by the biological, material and medical fields. However, magnesium is a very active metal in chemical properties, and magnesium and its alloys are extremely susceptible to corrosion in a corrosive environment, which greatly limits their application in clinical practice. The main methods for improving the corrosion resistance and prolonging the service life of magnesium alloy include micro-alloying, structure regulation, surface treatment and preparation of functional coatings, among which the most widely used and effective method is to prepare a corrosion prevention coating on the surface of magnesium alloy through surface treatment. Surface treatment provides another possibility for the application of magnesium alloy material as an implant material, and various surface treatment technologies effectively compensate for and improve the defects of magnesium alloy materials. However, medical metal materials inevitably rub and wear against the surrounding tissues during the implantation surgery, resulting in damage to the film layer and exposure of the base metal, and in the human corrosion environment, the magnesium alloy is subjected to corrosion by the corrosion medium.

[0004] Therefore, there is an urgent need in the prior art to develop a coating preparation method that can improve the corrosion resistance of magnesium alloy and has self-healing ability. SUMMARY

[0005] The present application aims to provide a preparation method of a self-healing active corrosion prevention coating for medical magnesium alloy to solve the technical problems mentioned in the background.

[0006] To achieve the above-mentioned purpose, the specific technical scheme of the preparation method of a self-healing active corrosion prevention coating for medical magnesium alloy of the present application is as follows:

[0007] The preparation method of a self-healing active corrosion prevention coating for medical magnesium alloy comprises the following steps, and the steps are performed in sequence:

[0008] Step 1) magnesium alloy surface pretreatment, polishing the magnesium alloy surface smooth, and then ultrasonic cleaning;

[0009] The purpose of step 1) is to smooth the surface of the magnesium alloy, remove impurities, and make the surface uniform and flat, which is conducive to building a regularly shaped micro-pit array structure on the surface of the magnesium alloy.

[0010] Step 2) Perform laser processing on the pretreated magnesium alloy, and clean and dry the magnesium alloy after processing.

[0011] Step 2) is used to construct a regularly shaped micro-pit structure on the surface of the magnesium alloy by laser processing.

[0012] Step 3) The magnesium alloy surface obtained in Step 2) is subjected to a hydrothermal reaction. After the reaction, the magnesium alloy is cleaned and dried to prepare the LTS-Mg coating.

[0013] Step 3) serves to: through a hydrothermal reaction with NaOH solution, to coat the surface of the laser-processed magnesium alloy with hexagonal nanosheets layer by layer, thereby obtaining an LTS-Mg coating.

[0014] Step 4) Immerse the magnesium alloy surface obtained in Step 3) in MnCl2·4H2O solution. After immersion, remove and air dry to obtain LTS / Mg-Mn coating.

[0015] Step 4) serves to: convert Mn 2+ The LTS / Mg-Mn coating is deposited into the micro-nano structure on the coating surface.

[0016] This invention employs a series of simple, easy-to-operate, and low-cost processing techniques to prepare an LTS / Mg-Mn coating with durable corrosion resistance and active self-healing capabilities on the surface of AZ91D magnesium alloy. Combining laser processing and hydrothermal treatment yields an LTS-Mg coating with a micro / nano composite structure, which is a Mn... 2+ Provide a more robust container for soaking Mn 2+ The deposition on the sample surface endows the magnesium alloy with surface-active self-healing ability, and the Mg(OH)2 film releases Mn 2+ With Mg 2+ and OH - The reaction generates Mn3O4 / Mg-Mn LDH with a 3D micro / nano composite structure, which repairs the scratched area and removes Cl from the film. - .

[0017] Furthermore, the method for pre-treating the magnesium alloy surface in step 1) is mechanical polishing with water sandpaper, using 400#, 800#, 1200#, 1500# and 2000# sandpaper to polish the magnesium alloy step by step until the surface is smooth.

[0018] Furthermore, in step 1), anhydrous ethanol is used for ultrasonic cleaning, and the ultrasonic cleaning time is 5-10 minutes.

[0019] Further, the wavelength of the laser beam used in the laser processing treatment in step 2) is 1064 nm, the repetition frequency is 20 kHz, and the pulse width is 100 ns. The laser processing adopts a dot array scanning mode, the dot spacing is 40 μm, and the laser energy density and the scanning speed are 22.95 J / cm 2 and 500 mm / s. In the present application, the inventors have found that only by using the above laser processing parameters can a regular-shaped micro-pit array be constructed on the surface of the magnesium alloy.

[0020] Further, in step 2), deionized water is used for washing, and drying is performed at 60-70℃, and the drying time is 30-60 min.

[0021] Further, in the hydrothermal reaction of step 3), the laser-processed magnesium alloy surface is placed in 33 ml of 2 mol / L NaOH solution, the environmental temperature is 180℃, and the reaction time is 200 min. In the present application, the inventors have found that only by using the above reaction time and environmental temperature can a regular-shaped, uniform and dense Mg(OH)2 film layer with a larger thickness be prepared on the laser-processed magnesium alloy surface, which is more conducive to the storage of Mn 2+ .

[0022] Further, in step 3), deionized water is used for washing, and drying is performed at 60-70℃, and the drying time is 30-60 min.

[0023] Further, in step 4), the concentration of the MnCl2·4H2O solution is 12 g / L, the sample is soaked in the solution for 6 h, and natural air drying is performed at room temperature.

[0024] The magnesium alloy prepared by the above preparation method has the abilities of durable corrosion resistance and intelligent self-healing, the surface of the magnesium alloy is covered with a regular-shaped micro-pit array, the micro-pit diameter is about 40 μm, the hexagonal nanosheet layer is covered on the surface of the micro-pit, the size is between 100 nm-200 nm, and the film layer thickness is about 23 μm.

[0025] The LTS / Mg-Mn coating prepared by the present application has a micro-nano composite structure and a film layer thickness, which are obtained by the inventors through research on the surface performance. The inventors have found that only in the above thickness range and size range can excellent corrosion resistance and intelligent self-healing ability be achieved.

[0026] The preparation method of the self-healing ability medical magnesium alloy active corrosion-resistant coating of the present application has the following advantages:

[0027] (1) The present application adopts a composite method of laser processing, hydrothermal reaction and soaking to prepare LTS / Mg-Mn coating on the magnesium alloy substrate, and the micropore array and Mg-Mn Mg(OH)2 micro-nano composite structure on the surface can effectively isolate the corrosion solution from corroding the magnesium alloy substrate, so as to realize the optimization of the corrosion resistance of the magnesium alloy substrate, improve the intelligent self-healing ability, and effectively prolong the service life of the magnesium alloy;

[0028] (2) The present application combines laser processing and hydrothermal reaction, and on the basis of laser processing, the micro-pit structure is used to increase the roughness of the magnesium alloy surface and increase the adhesion area of Mg-Mn Mg(OH)2, so that the magnesium alloy substrate has good corrosion resistance, and the surface is endowed with intelligent self-healing ability, further improving the corrosion resistance and durability of the magnesium alloy;

[0029] (3) The raw material of the present application is easy to obtain and low in price, the preparation process is simple and easy to operate, the safety in the preparation process is high, the energy consumption and pollution can be effectively reduced, expensive production equipment is not needed, the production cost is low, and the present application has high practical value, and provides a novel and effective method for preparing magnesium alloy material as potential medical implant material. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The SEM and EDS of the LTS / Mg-Mn coating prepared in the present application example 2 are shown in the figure.

[0031] Figure 2 The SEM and EDS of the LTS / Mg-Mn coating obtained by different hydrothermal reaction time in the present application test example are shown in the figure.

[0032] Figure 3 The SEM and EDS of the LTS / Mg-Mn coating obtained by different hydrothermal reaction time in the present application test example are shown in the figure.

[0033] Figure 4 The polarization curve comparison diagram of the LTS / Mg-Mn coating prepared in the present application test example is shown in the figure.

[0034] Figure 5SEM and EDS graphs (a1 and a2, SEM graph of LTS / Mg-Mn coating after 0 days of immersion; a3, EDS graph; b1 and b2, SEM graph of LTS-Mg coating after 0 days of immersion; b3, EDS graph; c1 and c2, SEM graph of LTS / Mg-Mn coating after 2 days of immersion; c3, EDS graph; c4, EDS element distribution graph; d1 and d2, SEM graph of LTS-Mg coating after 2 days of immersion; d3, EDS graph; d4, EDS element distribution graph; e1 and e2, SEM graph of LTS / Mg-Mn coating after 5 days of immersion; e3, EDS graph; e4, EDS element distribution graph; f1 and f2, SEM graph of LTS-Mg coating after 5 days of immersion; f3, EDS graph; f4, EDS element distribution graph; g1 and g2, SEM graph of LTS / Mg-Mn coating after 10 days of immersion; g3, EDS graph; g4, EDS element distribution graph; h1 and h2, SEM graph of LTS-Mg coating after 10 days of immersion; h3, EDS graph; h4, EDS element distribution graph) in immersion test of LTS / Mg-Mn coating prepared in experimental example of the present application.

[0035] Figure 6 XRD spectrum in immersion test of LTS / Mg-Mn coating prepared in experimental example of the present application.

[0036] Figure 7 SEM and EDS graphs (a1-a3, SEM graph of surface scratch area of LTS / Mg-Mn under 2N force; a4, EDS element distribution graph; b1-b3, SEM graph of surface scratch area of LTS-Mg under 2N force; b4, EDS element distribution graph; c1-c3, SEM graph of surface scratch area of LTS / Mg-Mn under 5N force; c4, EDS element distribution graph; d1-d3, SEM graph of surface scratch area of LTS-Mg under 5N force; d4, EDS element distribution graph) after scratch test of LTS / Mg-Mn coating prepared in experimental example of the present application.

[0037] Figure 8 EDS comparison graphs (a1, EDS element distribution graph of area 1; a2, EDS graph; b1, EDS element distribution graph of area 2; b2, EDS graph; c1, EDS element distribution graph of area 3; c2, EDS graph) of different areas after scratch test of LTS / Mg-Mn coating prepared in experimental example of the present application. DETAILED DESCRIPTION

[0038] In order to better understand the purpose, structure and function of the present application, the preparation method of a self-healing medical magnesium alloy active corrosion-resistant coating is further described in detail below in combination with the drawings.

[0039] The present application adopts a method combining laser processing and hydrothermal reaction to prepare a micro-nano composite structure on a magnesium alloy surface, the magnesium alloy surface is covered with regular-shaped micro-pit structures, the micro-pit surface is further enlarged, and a large number of nano-sized hexagonal nanosheets are layered on the micro-pit surface, and then soaking treatment is performed, so as to obtain an LTS / Mg-Mn coating. The purpose is to improve the corrosion resistance of the magnesium alloy surface and endow the surface with self-healing ability, so as to realize durable and stable corrosion resistance.

[0040] Example 1

[0041] Magnesium alloy surface pretreatment: a wire cutting machine (HA400U) in a numerical control servo system is used to cut magnesium alloy materials used for the test into sample pieces with a diameter of 14 mm. The magnesium alloy substrate surface is mechanically polished with 400#, 800#, 1200#, 1500# and 2000# sandpaper in sequence, then the magnesium alloy sample is ultrasonically cleaned with ethanol for 10 min, and finally dried in a constant temperature drying oven at 60°C for 30 min and put into a sealed bag for standby.

[0042] The wavelength of the laser beam used in the laser processing treatment is 1064 nm, the repetition frequency is 20 kHz, and the pulse width is 100 ns. The magnesium alloy sample is fixed on a sample table, and a galvanometer equipped with a focusing lens is used to transmit the focused laser beam to the sample surface. After focusing, the diameter of the laser beam spot is about 52 μm. The laser beam is controlled by a computer program to scan along two perpendicular directions (X and Y directions) on the magnesium alloy surface in a dot array scanning mode. The laser processing power and scanning speed are 10 W and 500 mm / s respectively. After laser processing, the sample is cleaned with deionized water and dried in a 60°C environment for 30 min, thereby obtaining a laser processed surface.

[0043] The laser processed surface is put into a 100 ml polytetrafluoroethylene high-temperature kettle liner, 33 ml of NaOH (2 mol / L) solution is added, the high-temperature kettle is sealed, and heated in a 180°C drying oven for constant temperature heating. The heating time is 200 min. After the hydrothermal reaction is completed, the sample is washed with deionized water and dried in a 60°C drying oven for 60 min, which is recorded as LTS-Mg coating.

[0044] Example 2

[0045] Magnesium alloy surface pretreatment: a wire cutting machine (HA400U) in a numerical control servo system is used to cut magnesium alloy materials used for the test into sample pieces with a diameter of 14 mm. The magnesium alloy substrate surface is mechanically polished with 400#, 800#, 1200#, 1500# and 2000# sandpaper in sequence, then the magnesium alloy sample is ultrasonically cleaned with ethanol for 10 min, and finally dried in a constant temperature drying oven at 60°C for 30 min and put into a sealed bag for standby.

[0046] The wavelength of the laser beam used in the laser processing treatment was 1064 nm, the repetition frequency was 20 kHz, and the pulse width was 100 ns. The magnesium alloy sample was fixed on a sample table, and a galvanometer equipped with a focusing lens was used to transmit the focused laser beam to the sample surface. After focusing, the diameter of the laser beam spot was about 52 μm. The laser beam was controlled by a computer program to scan the magnesium alloy surface line by line along two perpendicular directions (X and Y directions). The laser processing power and scanning speed were 10 W and 500 mm / s, respectively. After laser processing, the sample was cleaned with deionized water and dried in a 60°C environment for 30 min, thereby obtaining a laser-processed surface.

[0047] The laser-processed surface was placed in a 100 ml polytetrafluoroethylene inner liner of an autoclave, 33 ml of a NaOH (2 mol / L) solution was added, the autoclave was sealed, and was placed in a 180°C drying oven for constant temperature heating. The heating time was 200 min. After the hydrothermal reaction was completed, the sample was washed with deionized water and dried in a 60°C drying oven for 60 min, and was recorded as an LTS-Mg coating.

[0048] To endow the LTS-Mg coating with self-healing ability and further improve the corrosion resistance of the surface, the sample after the hydrothermal treatment was immersed in a MnCl2·4H2O (12 g / L) solution for 6 h. After the immersion was completed, the sample was naturally air-dried to obtain an LTS / Mg-Mn coating, as shown in Figure 1

[0049] Test Example:

[0050] During the hydrothermal reaction process, a constant temperature drying oven was used to ensure a certain time parameter in the hydrothermal reaction. The drying oven used had a time and temperature setting. The autoclave used in this test was a common reaction container used for special tests. The autoclave had good sealing performance during the reaction process. The autoclave body had a pressure relief hole, which had an explosion-proof function to prevent explosion during the reaction process. The inner liner of the autoclave was made of polytetrafluoroethylene material, which did not participate in the reaction during the hydrothermal process and was not easily corroded. The inner liner had a capacity of 100 ml. During the hydrothermal reaction process (environmental temperature 180°C, 2 mol / L NaOH solution), the reaction times were 130 min, 160 min, 200 min, and 250 min, respectively, to obtain an LTS-Mg coating. Subsequently, the obtained sample was immersed in a MnCl2·4H2O (12 g / L) solution for 6 h to prepare an LTS / Mg-Mn surface, as shown in Figure 2 ​The SEM images show that the time parameter has a great influence on the surface micro-morphology of the sample during the hydrothermal treatment. With the increase of the hydrothermal reaction time, the thickness of the Mg-Mn Mg(OH)2 film layer increases. When the hydrothermal reaction time is 130 min, a large number of nano-particle substances are observed on the micro-pit surface, and the film layer has a thickness of less than 10 μm. When the hydrothermal reaction time is 200 min, a micro-nano composite structure with a regular shape and complex structure is prepared on the surface, and the Mg-Mn Mg(OH)2 film layer has good compactness and uniform distribution. The thickness of the film layer increases from 8.5 μm to 23 μm. However, when the hydrothermal reaction time is increased to 250 min, a large number of cracks and micro-pores are generated on the surface, and the Mg-Mn Mg(OH)2 film layer has poor compactness. Therefore, too long or too short hydrothermal reaction time is not conducive to the preparation of the Mg-Mn Mg(OH)2 film layer.

[0051] A constant temperature drying oven was used to ensure a certain environmental temperature during the hydrothermal process. The drying oven has a time and temperature setting. The high-temperature kettle used in this experiment is a common reaction container for special tests. The high-temperature kettle has good airtightness during the reaction process, and the pressure relief hole on the kettle body has an explosion-proof function to prevent explosion during the reaction process. The inner lining of the high-temperature kettle is made of polytetrafluoroethylene material, which does not participate in the reaction during the hydrothermal process and is not easily corroded. The inner lining has a capacity of 100 ml. During the hydrothermal reaction process (reaction time 200 min, 2 mol / L NaOH solution), the environmental temperature is 90°C, 120°C, 150°C and 180°C in sequence. The obtained LTS-Mg coating is then immersed in a MnCl2·4H2O (12 g / L) solution for 6 h to prepare an LTS / Mg-Mn coating, as shown in Figure 3 As can be seen, the LTS / Mg-Mn film layer obtained at 180°C has good integrity, the LTS / Mg-Mn surfaces prepared at 120°C and 150°C are damaged, cracks are generated on the surface, and the micro-nano composite structure with a regular shape cannot be presented. When the environmental temperature is 90°C, the Mg-Mn Mg(OH)2 film layer has a small thickness, and no hexagonal nanosheet is observed on the surface. Therefore, when the environmental temperature is 180°C, the Mg-Mn Mg(OH)2 film layer with a regular shape and complex structure, good compactness and uniform distribution can be prepared on the surface of the magnesium alloy.

[0052] The LTS / Mg-Mn coating prepared in Example 2 was immersed in physiological saline, and the sample was subjected to potentiodynamic polarization curve test in sequence using an electrochemical workstation (PARSTAT3000A-DX, USA). The solution temperature during the entire test process was 36±1℃. The test was carried out under a standard three-electrode system, and the sample was used as the working electrode, with an exposed surface area of 1 cm 2 . A platinum electrode (1.0×1.0×0.1 mm 3 ) was used as the counter electrode, and a saturated calomel electrode (SCE) was used as the reference electrode. After the sample was immersed in the physiological saline solution for 30 min to obtain a stable state, the open circuit potential was tested. The frequency range for EIS test was 10 5 Hz to 10 -2 Hz, and the alternating current amplitude of the sinusoidal signal was 10 mV. A rate of 0.5 mV·s -1 was used to record the polarization curve in a potential range of ±300 mV relative to the open circuit potential. Figure 4 It can be seen that the corrosion current density of the magnesium alloy substrate surface is 4.49×10 -4 A / cm 2 , and the corrosion current density of the LST / Mg-Mn film layer is relatively small (2.79×10 -7 A / cm 2 ), which is 3 orders of magnitude lower than that of the substrate surface.

[0053] The LST / Mg-Mn coating was immersed in physiological saline for different times, and the morphology change of the coating surface was observed by electron microscopy, as shown in Figure 5 . After immersion for 2 days, the LST / Mg-Mn coating surface generated flower-like 3D micro-nano structures and Mn3O4 nanoparticles. EDS detection showed that the elements of the flower-like 3D micro-nano structure were mainly Mg, Mn and O. XRD spectrum Figure 6Diffraction peaks corresponding to LDH were detected at 11.4° and 23.1°, indicating that the flower-like 3D micro / nano structure is a Mg-Mn layered double hydroxide (LDH). With increasing immersion time, the amount of Mn3O4 / Mg-Mn LDH on the surface continuously increased, and the diffraction peaks of LDH became stronger. After 10 days of immersion, no obvious corrosion was observed on the LTS / Mg-Mn coating surface, indicating that the generated LDH has strong corrosion resistance. More importantly, EDS results showed that Cl elements were detected on the LTS / Mg-Mn surface before the immersion test, but disappeared after 2 days of immersion. This indicates that the generated Mn3O4 / Mg-Mn LDH can transport and expel corrosive Cl ions from the coating. In contrast, after 2 days of immersion in the corrosive solution, no obvious changes were observed on the LTS-Mg coating surface. However, with continued increase in immersion time, after 10 days, a large number of corrosion products and corrosion cracks were generated on the LTS-Mg coating surface, indicating severe damage to the LTS-Mg coating.

[0054] The automatic scratch tester for film adhesion (WS-2005) is used for scratch testing of coating surfaces. The applied loads are 2N and 5N respectively. Scratch tests are performed on LTS-Mg surface and LTS / Mg-Mn surface in sequence. The operation mode is constant load, the sliding speed is 0.1mm / s, the scratch length is 5mm, the number of scratches is 1, and the indenter used is a diamond indenter with a cone angle of 120° and a radius of 0.2mm. Figure 7 The SEM and EDS images of the LST-Mg and LTS / Mg-Mn surfaces after immersion in physiological saline following the scratch test are shown. Under a force of 2 N, the sample surfaces were damaged, with scratch widths of approximately 70 μm. However, micro / nano composite structures were detected in the scratched areas of the LTS / Mg-Mn surface, with microstructures similar to... Figure 5 Similar results were observed. EDS results showed that the main elements of the newly formed product were Mn, O, and Mg, suggesting that the product was Mn3O4 / Mg-Mn LDH. However, microcracks were observed in the scratched area of ​​the LST-Mg surface. When the applied force increased to 5 N, the scratch width was 100 μm, and Mn3O4 / Mg-Mn LDH was still observed to form in the scratched area of ​​the LST / Mg-Mn surface, covering the scratched area layer by layer. Furthermore, no obvious corrosion was observed in the scratched area. In addition, LDH mainly appeared in the scratched area, and EDS analysis revealed that the Mn content was highest in the scratched area. Figure 8 In contrast, numerous corrosion pits, corrosion products, and corrosion cracks were observed in the scratched areas of the LST-Mg surface, indicating severe corrosion damage to the coating surface.

[0055] It is to be understood that the present application is described by way of example only, and that modifications or alterations can be made to the features and embodiments described without departing from the spirit and scope of the application. In addition, modifications can be made to the features and embodiments described to accommodate specific situations and materials without departing from the spirit and scope of the application. Accordingly, the application is not limited to the specific embodiments disclosed herein, but rather, the scope of the application includes all embodiments falling within the scope of the claims.

Claims

1. A method for preparing a self-healing medical magnesium alloy active anti-corrosion coating, characterized in that, Includes the following steps, And the following steps are performed in sequence: Step 1) Magnesium alloy surface pretreatment: smooth the magnesium alloy surface and then ultrasonically clean it. Step 2) Perform laser processing on the magnesium alloy pretreated in Step 1), and clean and dry the magnesium alloy after processing. Step 3) Place the magnesium alloy surface obtained in step 2) into NaOH solution for hydrothermal reaction, and then clean and dry the magnesium alloy after the reaction. Step 4) Immerse the magnesium alloy surface obtained in Step 3) in MnCl2•4H2O solution, remove it after immersion and let it air dry to obtain LTS / Mg-Mn coating; The LTS / Mg-Mn coating is a regularly shaped micro-nano composite structure covering the surface of a magnesium alloy. The micro-pit diameter is 40μm, and hexagonal nanosheets with a size of 100nm-200nm are layered on the surface of the micro-pit, with a film thickness of 23μm.

2. The method for preparing the self-healing medical magnesium alloy active anti-corrosion coating according to claim 1, characterized in that, The method for pre-treating the magnesium alloy surface in step 1) is mechanical polishing with water sandpaper, using 400#, 800#, 1200#, 1500# and 2000# sandpaper to polish the magnesium alloy step by step until the surface is smooth.

3. The method for preparing the self-healing medical magnesium alloy active anti-corrosion coating according to claim 1, characterized in that, In step 1), anhydrous ethanol is used for ultrasonic cleaning, and the ultrasonic cleaning time is 5-10 minutes.

4. The method for preparing the self-healing medical magnesium alloy active anti-corrosion coating according to claim 1, characterized in that, The laser beam used in step 2) has a wavelength of 1064 nm, a repetition frequency of 20 kHz, and a pulse width of 100 ns. The laser processing employs a dot array scanning method with a dot spacing of 40 μm. The laser energy density and scanning speed are 22.95 J / cm². 2 And 500mm / s.

5. The method for preparing the self-healing medical magnesium alloy active anti-corrosion coating according to claim 1, characterized in that, In step 2), deionized water is used for rinsing, followed by drying at 60-70℃ for 30-60 minutes.

6. The method for preparing the self-healing medical magnesium alloy active anti-corrosion coating according to claim 1, characterized in that, In step 3), the laser-processed magnesium alloy surface is placed in 33 ml of 2 mol / L NaOH solution at an ambient temperature of 180 °C for a reaction time of 200 min.

7. The method for preparing the self-healing medical magnesium alloy active anti-corrosion coating according to claim 1, characterized in that, In step 3), deionized water is used for rinsing, and the product is dried at 60-70℃ for 30-60 minutes.

8. The method for preparing the self-healing medical magnesium alloy active anti-corrosion coating according to claim 1, characterized in that, In step 4), the concentration of the MnCl2•4H2O solution is 12 g / L, the sample is immersed in the solution for 6 hours, and then air-dried at room temperature.

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