Calcium-based phosphate hole sealing treatment method based on biomedical magnesium alloy micro-arc oxidation coating

Abstract

The invention belongs to the technical field of material surface treatment, and particularly relates to a calcium-based phosphate hole sealing treatment method based on a biomedical magnesium alloy micro-arc oxidation coating. Carrying out micro-arc oxidation treatment on the magnesium alloy to obtain a micro-arc oxidation coating; and then hole sealing treatment is conducted in a hole sealing solution composed of calcium-based phosphate, the magnesium alloy surface micro-arc oxidation-calcium-based phosphate hole sealing composite coating is obtained, and the hole sealing solution is a mixed aqueous solution of soluble calcium salt, NH4H2PO4, NaNO3, C10H14N2Na2O8. 2H2O and H3PO4. After magnesium alloy is subjected to micro-arc oxidation treatment, a micro-arc oxidation coating formed on the surface has the defects of cracks, pores and the like, and the corrosion resistance of the coating is not facilitated. In order to further eliminate the influence of the defects in the coating, a novel calcium-based phosphate hole sealing treatment technology is adopted, so that the corrosion resistance of the coating can be remarkably enhanced, and the biocompatibility of the coating can be improved by introducing a calcium element.

Description

Technical Field

[0001] The present invention relates to the technical field of material surface treatment, and particularly relates to a calcium-based phosphate sealing treatment method for a micro-arc oxidation coating of a biomedical magnesium alloy. Background Art

[0002] As an emerging biodegradable implant material, biomedical magnesium alloy has mechanical properties matching those of human bone, excellent biocompatibility and biodegradability. However, its rapid degradation problem in the physiological environment has become a major challenge in clinical applications. This rapid degradation makes it unable to provide stable support for tissue repair, thus affecting the implantation effect. To solve this problem, it is particularly important to perform surface treatment on the magnesium alloy. The surface treatment aims to improve the corrosion resistance, wear resistance and biocompatibility of the magnesium alloy, so as to extend its service life and ensure its safety and effectiveness in the body. Among many surface treatment technologies, micro-arc oxidation has attracted much attention due to its unique advantages.

[0003] The micro-arc oxidation technology uses the high temperature and high pressure generated by arc discharge to directly form an oxide ceramic coating on the surface of the magnesium alloy that is firmly bonded to the substrate. This coating can not only effectively resist corrosion media, but also has high hardness and wear resistance, protecting the stability of the implant in the body. In addition, the micro-arc oxidation treatment process is simple, efficient, and has little environmental pollution, meeting the concept of green and sustainable development. However, the micro-arc oxidation coating often has a porous structure, making the coating vulnerable to erosion in specific environments such as humid and corrosive media, and the long-term corrosion resistance of the coating is insufficient, thus unable to meet the degradation performance requirements of biomedical magnesium alloys.

[0004] Sealing the micro-arc oxidation coating is an effective method to improve the long-term corrosion resistance of the coating. Most of the sealing solutions used in current sealing treatment methods are rare-earth-based solutions or use rare-earth oxide particles for sealing. However, the content of rare-earth elements in the human body is very small (less than 1 mg), and the effects of different rare-earth elements on the human body have not been fully understood. In recent years, some phosphate solutions have also been used for sealing the micro-arc oxidation coating of magnesium alloys, but in these sealing treatment methods, the sealing solution only relies on the established cation quantity in the solution and the magnesium ions dissolved from the magnesium alloy substrate to achieve the deposition and sealing of the corresponding phosphate, and the deposition and sealing effects are not good. Summary of the Invention

[0005] Aiming at the deficiencies of the above-mentioned existing technologies, the purpose of the present invention is to provide a calcium-based phosphate sealing treatment method for a micro-arc oxidation coating of biomedical magnesium alloy. First, the present invention uses micro-arc oxidation treatment to obtain a coating with good corrosion resistance on the magnesium alloy, and then performs a sealing treatment to fill the coating pores with the sealing solution. Through the phosphate deposition reaction, the deposited substances fill the pores and cracks in the micro-arc oxidation coating and are deposited on the surface of the micro-arc oxidation coating, improving the density of the micro-arc oxidation coating, enhancing the long-term degradation performance of the coating, and increasing the calcium element content in the solution through the complexing agent in the sealing solution to improve the sealing effect. At the same time, due to the advantages of calcium element such as promoting osteogenesis, using calcium-based phosphate for sealing treatment can further improve the biocompatibility of the coating.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A calcium-based silicate sealing treatment method for a micro-arc oxidation coating of biomedical magnesium alloy, comprising the following steps:

[0008] Cut the magnesium alloy specimen and then perform step-by-step grinding, followed by cleaning and drying.

[0009] Use the treated magnesium alloy specimen as the anode and a graphite plate as the cathode, place them in the electrolyte for micro-arc oxidation treatment, and then rinse and dry to obtain a micro-arc oxidation coating.

[0010] Perform a sealing treatment on the micro-arc oxidation coating in the sealing solution to obtain a micro-arc oxidation - calcium-based phosphate sealing composite coating on the surface of the magnesium alloy.

[0011] Among them, the sealing solution is a mixed aqueous solution of soluble calcium salt, NH4H2PO4, NaNO3 and C 10 H 14 N2Na2O8·2H2O.

[0012] First, the present invention uses micro-arc oxidation treatment to obtain a coating with good corrosion resistance on the magnesium alloy, and then performs a sealing treatment to fill the coating pores with the sealing solution. Through the phosphate deposition reaction, the deposited substances fill the pores and cracks in the micro-arc oxidation coating and are deposited on the surface of the micro-arc oxidation coating, improving the density of the micro-arc oxidation coating, enhancing the long-term degradation performance of the coating, and increasing the calcium element content in the solution through the Ca(NO3)2·4H2O complexing agent in the sealing solution to improve the sealing effect. At the same time, due to the advantages of calcium element such as promoting osteogenesis, using calcium-based phosphate for sealing treatment can further improve the biocompatibility of the coating.

[0013] In a preferred embodiment of the present invention, the soluble calcium salt is Ca(NO3)2·4H2O or CaCl2. In the sealing solution, the dosage ratio of Ca(NO3)2·4H2O, NH4H2PO4, NaNO3, C 10 H 14 N2Na2O8·2H2O to water is 30 g to 40 g: 30 g to 40 g: 2 g to 4 g: 2 g to 5 g: 1 L.

[0014] In a preferred embodiment of the present invention, the sealing treatment temperature is 60 °C to 70 °C.

[0015] In a preferred embodiment of the present invention, before the sealing treatment, 10% H3PO4 is used to adjust the pH value of the sealing solution to 3 to 4.

[0016] In a preferred embodiment of the present invention, the soaking time of the micro-arc oxidation treatment coating in the sealing solution is 10 min to 30 min.

[0017] In a preferred embodiment of the present invention, the electrolyte is an aqueous solution mixture of Na2SiO3·9H2O, KF·2H2O, and NaOH.

[0018] In a preferred embodiment of the present invention, in the electrolyte, the dosage ratio of Na2SiO3·9H2O, KF·2H2O, NaOH to water is 20 g to 25 g: 7 g to 8 g: 8 g to 10 g: 1 L.

[0019] In a preferred embodiment of the present invention, the micro-arc oxidation treatment process parameters are: voltage 0 to 450 V, current density 3 A / cm 2 ~5 A / cm 2 , pulse frequency 100 Hz to 500 Hz, duty cycle -30% to 30%.

[0020] In a preferred embodiment of the present invention, the micro-arc oxidation treatment time is 30 min to 35 min.

[0021] In a preferred embodiment of the present invention, the magnesium alloy is a Mg-0.45Zn-0.45Ca alloy.

[0022] In a preferred embodiment of the present invention, the method of successively grinding the specimen after cutting is to grind with 240#, 600#, 1000#, and 2000# SiC sandpapers in sequence.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] 1. The calcium-based phosphate sealing treatment method of the present invention first uses micro-arc oxidation treatment to prepare a micro-arc oxidation coating, and then performs a sealing treatment on the micro-arc oxidation coating to fill the coating pores with a sealing solution. Through a phosphate deposition reaction, the deposited substances fill the pores and cracks in the micro-arc oxidation coating and are deposited on the surface of the micro-arc oxidation coating, improving the density of the micro-arc oxidation coating, enhancing the long-term degradation performance of the coating, and increasing the calcium element content in the solution through the soluble calcium salt complexing agent in the sealing solution to improve the sealing effect. At the same time, since calcium has advantages such as promoting osteogenesis, using calcium-based phosphate for sealing treatment can further improve the biocompatibility of the coating.

[0025] 2. The present invention first performs micro-arc oxidation treatment to obtain a micro-arc oxidation coating with good corrosion resistance, and then adopts a new calcium-based phosphate sealing process to finally form a wear-resistant and corrosion-resistant composite coating on the surface. After the magnesium alloy is treated by micro-arc oxidation, the micro-arc oxidation coating formed on its surface often has defects such as cracks and pores, which is not conducive to the long-term corrosion resistance of the coating. In order to further eliminate the influence of these defects in the coating, a new calcium-based phosphate sealing treatment technology is adopted, which can not only deposit phosphates in the coating defects to improve the coating density and significantly enhance the corrosion resistance of the coating, but also improve the biocompatibility of the coating by introducing calcium elements. Description of the Drawings

[0026] Figure 1 It is a macroscopic appearance diagram of the surface film of the magnesium alloy prepared in Example 1 of the present invention.

[0027] Figure 2 It is a scanning electron microscope image of the surface film of the magnesium alloy prepared in Comparative Example 1 (a) and Example 1 (b) of the present invention.

[0028] Figure 3 It is a cross-sectional scanning electron microscope image of the cross-sectional film of the magnesium alloy prepared in Comparative Example 1 (a) and Example 1 (b) of the present invention.

[0029] Figure 4 It is an energy spectrum diagram of the surface film of the magnesium alloy prepared in Example 1 of the present invention.

[0030] Figure 5 It is a potentiodynamic polarization curve diagram of the surface film of the magnesium alloy prepared in Example 1 of the present invention.

[0031] Figure 6 It is an electrochemical impedance spectroscopy diagram of the surface film of the magnesium alloy prepared in Example 1 of the present invention, (a) electrochemical impedance spectroscopy diagram, (b) Bode diagram.

[0032] Figure 7 It is a comparison diagram of the immersion experiments of the surface films of the magnesium alloys prepared in Comparative Example 1 (a) and Example 1 (b) of the present invention. Detailed implementation mode

[0033] Combined with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the preferred embodiments and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] It should be noted that all the professional terms used in the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be obtained through market purchase or prepared by existing methods.

[0035] In view of the problem that in the traditional sealing treatment method of magnesium alloy, the sealing solution only relies on the established cation quantity in the solution and the magnesium ions dissolved from the magnesium alloy matrix to achieve the deposition and sealing of the corresponding phosphate, and the deposition and sealing effects are not good, the present invention proposes a micro-arc oxidation-calcium-based phosphate sealing treatment method for the surface of magnesium alloy. Taking the magnesium alloy sample as the anode and the graphite plate as the cathode, they are placed in the electrolyte for micro-arc oxidation treatment to obtain a micro-arc oxidation coating; the micro-arc oxidation coating is sealed in a sealing solution containing soluble calcium salt, NH4H2PO4, NaNO3, C 10 H 14 N2Na2O8·2H2O to obtain a micro-arc oxidation-calcium-based phosphate sealing treatment coating on the surface of the magnesium alloy. Among them, in the sealing solution, the dosage ratio of soluble calcium salt, NH4H2PO4, NaNO3, C 10 H 14 N2Na2O8·2H2O to water is 30-40g:30-40g:2-4g:2-5g:1L; the results show that the pores of the micro-arc oxidation film after calcium-based phosphate sealing are significantly reduced. The immersion experiment after soaking in simulated body fluid for 90 days proves that the corrosion resistance of the samples after phosphate sealing treatment is significantly better, indicating that the present invention obtains a coating with good corrosion resistance on the surface of the magnesium alloy through micro-arc oxidation treatment, retains the good corrosion resistance of the surface coating of the alloy after micro-arc oxidation treatment, enables the sealing solution to fill the pores of the coating while phosphate deposition occurs, thereby filling the pores in the coating. This method can improve the densification of the micro-arc oxidation coating of magnesium alloy and greatly extend the time for the coating to effectively protect the magnesium alloy matrix, solve the problem of pores existing on the surface of the coating formed after micro-arc oxidation, and greatly extend the service life.

[0036] Example 1

[0037] A method for surface micro-arc oxidation - calcium phosphate sealing treatment of a Mg-0.45Zn-0.45Ca alloy, comprising the following steps:

[0038] (1) Cut the Mg-0.45Zn-0.45Ca alloy into a semi-cylindrical shape with a height of 10 mm and a diameter of 10 mm, polish it successively with 240#, 400#, 600#, 1000# and 2000# SiC sandpapers, then wash it with ethanol and blow it dry.

[0039] (2) Prepare an electrolyte of 22.5 g / L Na2SiO3·9H2O, 7.5 g / L KF·2H2O and 9 g / L NaOH; then use the specimen obtained in step (1) as the anode and a graphite plate as the cathode, place them in the electrolyte for micro-arc oxidation treatment, and carry out the treatment in a constant current mode. Among them, the voltage of the pulse power supply is 450 V, the current density is 3 A / cm 2 , the pulse frequency is 500 Hz, the duty cycle is 30% positive and 30% negative, carry out micro-arc oxidation for 30 min, and after the end, take out the specimen, rinse it with deionized water and blow it dry.

[0040] (3) First, prepare a sealing solution of 35.4 g / L Ca(NO3)2·4H2O, 35 g / L NH4H2PO4, 2 g / L NaNO3 and 2.23 g / L C 10 H 14 N2Na2O8·2H2O, adjust the pH value of the sealing solution to 3 with 10% H3PO4, then heat the sealing solution to 60 °C, place the specimen obtained in step (2) in it for 10 min, then take out the sample, rinse it with deionized water and blow it dry to obtain a micro-arc oxidation coating with calcium phosphate sealing treatment.

[0041] Example 2

[0042] A method for surface micro-arc oxidation - calcium phosphate sealing of a Mg-0.45Zn-0.45Ca alloy, comprising the following steps:

[0043] (1) Cut the Mg-0.45Zn-0.45Ca alloy into a shape of 10 mm × 10 mm × 5 mm, polish it successively with 240#, 400#, 600#, 1000# and 2000# SiC sandpapers, then wash it with ethanol and blow it dry.

[0044] (2) Prepare an electrolyte solution containing 22.5 g / L of Na2SiO3·9H2O, 7.5 g / L of KF·2H2O, and 9 g / L of NaOH; then use the specimen obtained in step (1) as the anode and a graphite plate as the cathode, place them in the electrolyte solution for micro-arc oxidation treatment, and perform the treatment in a constant current mode. Among them, the voltage of the pulsed power supply is 450 V, the current density is 3 A / cm 2 , the pulse frequency is 500 Hz, the duty cycle is 20% positive and 30% negative, perform micro-arc oxidation for 40 min, and after the end, take out the specimen, rinse it with deionized water, and dry it.

[0045] (3) First, prepare a sealing solution containing 35.4 g / L of Ca(NO3)2·4H2O, 35 g / L of NH4H2PO4, 2 g / L of NaNO3, and 2.23 g / L of C 10 H 14 N2Na2O8·2H2O. Use 10% H3PO4 to adjust the pH value of the sealing solution to 3, then heat the sealing solution to 65 °C, place the specimen obtained in step (2) in it for 15 min, and then take out the sample, rinse it with deionized water, and dry it to obtain a micro-arc oxidation coating with calcium phosphate sealing treatment.

[0046] Example 3

[0047] A method for surface micro-arc oxidation - calcium phosphate sealing of Mg-0.45Zn-0.45Ca alloy, comprising the following steps:

[0048] (1) Cut the Mg-0.45Zn-0.45Ca alloy into a shape of 15 mm × 15 mm × 5 mm, polish it successively with 240#, 400#, 600#, 1000#, and 2000# SiC sandpapers, then clean it with ethanol and dry it.

[0049] (2) First, prepare an electrolyte solution containing 23.5 g / L of Na2SiO3·9H2O, 7.5 g / L of KF·2H2O, and 9.5 g / L of NaOH; then use the specimen obtained in S1 as the anode and a graphite plate as the cathode, place them in the electrolyte solution for micro-arc oxidation treatment, and perform the treatment in a constant current mode. Among them, the voltage of the pulsed power supply is 450 V, the current density is 3 A / cm 2 , the pulse frequency is 500 Hz, the duty cycle is 20% positive and 20% negative, perform micro-arc oxidation for 35 min, and after the end, take out the specimen, rinse it with deionized water, and dry it.

[0050] (3) First, prepare a sealing solution containing 35.4 g / L of Ca(NO3)2·4H2O, 35 g / L of NH4H2PO4, 2 g / L of NaNO3, and 2.23 g / L of C 10 H 14The sealing solution of N2Na2O8·2H2O, using 10% H3PO4 to adjust the pH value of the sealing solution to 3.5, then heating the sealing solution to 70 °C, placing the sample obtained in step (2) therein for 20 min, and then taking out the sample, rinsing it with deionized water and drying it to obtain a micro-arc oxidation coating with calcium phosphate sealing treatment.

[0051] Example 4

[0052] A surface micro-arc oxidation-calcium phosphate sealing method for Mg-0.45Zn-0.45Ca alloy, comprising the following steps:

[0053] (1) Cut the Mg-0.45Zn-0.45Ca alloy into a shape of 20 mm × 20 mm × 10 mm, polish it successively with 240#, 400#, 600#, 1000# and 2000# SiC sandpapers, and then clean it with ethanol and dry it.

[0054] (2) Prepare an electrolyte of 23.5 g / L Na2SiO3·9H2O, 7.5 g / L KF·2H2O and 9 g / L NaOH. Then, using the sample obtained in step (1) as the anode and a graphite plate as the cathode, place them in the electrolyte for micro-arc oxidation treatment, and perform the treatment in a constant current mode. Among them, the voltage of the pulse power supply is 450 V, the current density is 3 A / cm 2 , the pulse frequency is 500 Hz, the duty cycle is 30% positive and 20% negative, micro-arc oxidize for 40 min, and after the end, take out the sample, rinse it with deionized water and dry it.

[0055] (3) First, prepare a sealing solution of 35.4 g / L Ca(NO3)2·4H2O, 35 g / L NH4H2PO4, 2 g / L NaNO3 and 2.23 g / L C 10 H 14 N2Na2O8·2H2O, use 10% H3PO4 to adjust the pH value of the sealing solution to 3.5, then heat the sealing solution to 70 °C, place the sample obtained in step (2) therein for 25 min, and then take out the sample, rinse it with deionized water and dry it to obtain a micro-arc oxidation coating with calcium phosphate sealing treatment.

[0056] Example 5

[0057] A surface micro-arc oxidation-calcium phosphate sealing treatment method for Mg-0.45Zn-0.45Ca alloy, comprising the following steps:

[0058] (1) Cut the Mg-0.45Zn-0.45Ca alloy into a semi-cylindrical shape with a height of 10 mm and a diameter of 10 mm. Polish it successively with 240#, 400#, 600#, 1000# and 2000# SiC sandpapers, then clean it with ethanol and blow it dry.

[0059] (2) Prepare an electrolyte solution containing 20 g / L of Na2SiO3·9H2O, 7 g / L of KF·2H2O and 8 g / L of NaOH; then use the specimen obtained in step (1) as the anode and a graphite plate as the cathode, place them in the electrolyte solution for micro-arc oxidation treatment, and carry out the treatment in a constant current mode. Among them, the voltage of the pulse power supply is 450 V, and the current density is 3 A / cm 2 , the pulse frequency is 500 Hz, the duty cycle is 30% positive and 30% negative, carry out micro-arc oxidation for 30 min, and after the end, take out the specimen, rinse it with deionized water and blow it dry.

[0060] (3) First, prepare a sealing solution containing 35.4 g / L of Ca(NO3)2·4H2O, 35 g / L of NH4H2PO4, 2 g / L of NaNO3 and 2.23 g / L of C 10 H 14 N2Na2O8·2H2O, adjust the pH value of the sealing solution to 4 with 10% H3PO4, then heat the sealing solution to 60 °C, place the specimen obtained in step (2) in it for 15 min, then take out the sample, rinse it with deionized water and blow it dry to obtain a micro-arc oxidation coating with calcium phosphate sealing treatment.

[0061] Example 6

[0062] A method for surface micro-arc oxidation-calcium phosphate sealing treatment of Mg-0.45Zn-0.45Ca alloy, comprising the following steps:

[0063] (1) Cut the Mg-0.45Zn-0.45Ca alloy into a semi-cylindrical shape with a height of 10 mm and a diameter of 10 mm. Polish it successively with 240#, 400#, 600#, 1000# and 2000# SiC sandpapers, then clean it with ethanol and blow it dry.

[0064] (2) Prepare an electrolyte solution containing 25 g / L of Na2SiO3·9H2O, 8 g / L of KF·2H2O and 10 g / L of NaOH; then use the specimen obtained in step (1) as the anode and a graphite plate as the cathode, place them in the electrolyte solution for micro-arc oxidation treatment, and carry out the treatment in a constant current mode. Among them, the voltage of the pulse power supply is 450 V, and the current density is 3 A / cm 2 , the pulse frequency is 500 Hz, the duty cycle is 30% positive and 30% negative, carry out micro-arc oxidation for 30 min, and after the end, take out the specimen, rinse it with deionized water and blow it dry.

[0065] (3) First, prepare a sealing solution containing 40 g / L of Ca(NO3)2·4H2O, 40 g / L of NH4H2PO4, 4 g / L of NaNO3, and 5 g / L of C 10 H 14 N2Na2O8·2H2O. Adjust the pH value of the sealing solution to 4 using 10% H3PO4. Then heat the sealing solution to 80 °C, place the sample obtained in step (2) therein for 10 min, and then take out the sample, rinse it with deionized water, and dry it to obtain a micro-arc oxidation coating with calcium phosphate sealing treatment.

[0066] Comparative Example 1

[0067] A method for surface micro-arc oxidation - calcium phosphate sealing of a Mg-0.45Zn-0.45Ca alloy, comprising the following steps:

[0068] (1) Cut the Mg-0.45Zn-0.45Ca alloy into a semi-cylindrical shape with a height of 10 mm and a diameter of 10 mm. Polish it successively with 240#, 400#, 600#, 1000#, and 2000# SiC sandpapers, then clean it with ethanol and dry it.

[0069] (2) Prepare an electrolyte solution containing 22.5 g / L of Na2SiO3·9H2O, 7.5 g / L of KF·2H2O, and 9 g / L of NaOH; then use the sample obtained in step (1) as the anode and a graphite plate as the cathode, place them in the electrolyte solution for micro-arc oxidation treatment, and perform the treatment in a constant current mode. Among them, the voltage of the pulse power supply is 450 V, the current density is 3 A / cm 2 , the pulse frequency is 500 Hz, the duty cycle is 30% positive and 30% negative, perform micro-arc oxidation for 30 min, and after completion, take out the sample, rinse it with deionized water, and dry it.

[0070] The preparation methods of Examples 2 - 5 of the present invention are the same as that of Example 1, except that, under the allowable experimental conditions, the amounts of some raw materials and reaction conditions are changed, but it does not affect the performance of the obtained micro-arc oxidation coating. Therefore, the micro-arc oxidation coatings obtained in Examples 2 - 5 are similar in performance to that of Example 1, and both can improve the denseness of the micro-arc oxidation coating of the magnesium alloy and greatly extend the time for the coating to effectively protect the magnesium alloy substrate.

[0071] Result Analysis

[0072] Figure 1 This is the macroscopic appearance diagram of the surface film of the Mg-0.45Zn-0.45Ca alloy prepared in Example 1 of the present invention. As Figure 1 shown, it can be seen that the coating color of the surface film of the Mg-0.45Zn-0.45Ca alloy is white.

[0073] Figure 2 Scanning electron micrographs of the surface films of the Mg-0.45Zn-0.45Ca alloys prepared in Example 1 and Comparative Example 1; among them, (a) is Comparative Example 1 and (b) is Example 1. As Figure 2 shown in (b), only micro-arc oxidation was performed Figure 2 Compared with (a) and Example 1, the pores on the surface film of the Mg-0.45Zn-0.45Ca alloy sample treated by the micro-arc oxidation-calcium phosphate sealing method in Example 1 were significantly reduced. This is mainly because after the calcium phosphate sealing treatment, calcium phosphate was deposited on the surface of the coating, thus filling the holes in the coating and improving the densification of the micro-arc oxidation coating of the magnesium alloy.

[0074] Figure 3 Cross-sectional scanning electron micrographs of the surface films of the Mg-0.45Zn-0.45Ca alloys prepared in Example 1 and Comparative Example 1; among them, (a) is Comparative Example 1 and (b) is Example 1. As Figure 3 shown in (b), the interface between the coating prepared in Example 1 and the substrate was very tightly bonded, and the surface coating of the sample of the Mg-0.45Zn-0.45Ca alloy treated by micro-arc oxidation-calcium phosphate sealing was about 15-20 μm.

[0075] Figure 4 Energy spectrum of the surface film of the Mg-0.45Zn-0.45Ca alloy prepared in Example 1. As Figure 4 shown, in Example 1, after micro-arc oxidation treatment and then calcium phosphate sealing treatment, the micro-arc oxidation coating of the Mg-0.45Zn-0.45Ca alloy mainly contains Mg, Si, and O, and the sealing material mainly contains Ca, P, and O.

[0076] Figure 5 Potentiodynamic polarization curve of the surface film of the Mg-0.45Zn-0.45Ca alloy prepared in Example 1. As Figure 5 shown, in Example 1, after micro-arc oxidation treatment and then calcium phosphate sealing treatment, its electrochemical impedance corrosion current density decreased significantly compared with that of the Mg-0.45Zn-0.45Ca alloy, from 2.8×10 -6 A / cm 2 to 1.0×10 -7 A / cm 2 , and its corrosion resistance was significantly improved.

[0077] Figure 6The electrochemical impedance spectra of the Mg-0.45Zn-0.45Ca alloy samples prepared in Example 1, which were subjected to micro-arc oxidation treatment and then calcium-based phosphate sealing treatment, and the samples prepared in Comparative Example 1 without calcium-based phosphate sealing treatment are as follows Figure 6 As shown, in Example 1, after micro-arc oxidation treatment and then calcium-based phosphate sealing treatment, its electrochemical impedance was significantly improved compared with the Mg-0.45Zn-0.45Ca alloy only subjected to micro-arc oxidation treatment, increasing from 2.01×10 6 Ω to 5.05×10 6 Ω.

[0078] Figure 7 The comparison of the immersion experiments after 90 days of immersion in simulated body fluid between the Mg-0.45Zn-0.45Ca alloy samples prepared by the micro-arc oxidation treatment method of the present invention and then subjected to calcium-based phosphate sealing treatment and the samples without calcium-based phosphate sealing treatment. Among them, (a) is Comparative Example 1 and (b) is Example 1, as follows Figure 7 As shown, the corrosion resistance of the samples subjected to calcium-based phosphate sealing treatment is significantly better.

[0079] In summary, the present invention first performs micro-arc oxidation treatment to obtain a coating with good corrosion resistance, and then adopts a new calcium-based phosphate sealing process to finally form a wear-resistant and corrosion-resistant coating on the surface. After the magnesium alloy is subjected to micro-arc oxidation treatment, the micro-arc oxidation coating formed on its surface maintains excellent corrosion resistance. In order to further eliminate the problem of pores existing on this layer of film, a phosphate sealing treatment technology is adopted, which not only successfully fills the micropores on the surface of the micro-arc oxidation coating and significantly enhances the corrosion resistance of the coating.

[0080] It should be noted that when the present invention involves a numerical range, it should be understood that any value between the two endpoints of each numerical range and any one of the two endpoints can be selected. Since the adopted step methods are the same as those in the examples, in order to prevent repetition, the present invention describes the preferred examples. Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be interpreted to include the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0081] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A calcium phosphate sealing treatment method for biomedical magnesium alloy micro-arc oxidation coating, characterized in that, It includes the following steps: Using a magnesium alloy specimen as the anode and a graphite plate as the cathode, place them in an electrolyte for micro-arc oxidation treatment to obtain a micro-arc oxidation coating; Perform sealing treatment on the micro-arc oxidation coating in a sealing solution to obtain a calcium-based phosphate sealing composite coating based on micro-arc oxidation of biomedical magnesium alloy; Among them, the hole-sealing solution is an aqueous mixed solution of soluble calcium salt, NH4H2PO4, NaNO3, and C 10 H 14 N2Na2O8·2H2O. The concentration of the soluble calcium salt is 30 g / L to 40 g / L, the concentration of NH4H2PO4 is 30 g / L to 40 g / L, the concentration of NaNO3 is 2 g / L to 4 g / L, and the concentration of C 10 H 14 N2Na2O8·2H2O is 2 g / L to 5 g / L.

2. The calcium phosphate sealing treatment method based on the micro-arc oxidation coating of biomedical magnesium alloy according to claim 1, characterized in that, The soluble calcium salt is Ca(NO3)2·4H2O or CaCl2.

3. The calcium phosphate sealing treatment method based on the micro-arc oxidation coating of biomedical magnesium alloy according to claim 1, characterized in that, The temperature for sealing treatment is 60°C to 70°C.

4. The calcium phosphate sealing treatment method based on the micro-arc oxidation coating of biomedical magnesium alloy according to claim 1, characterized in that, Before the sealing treatment, use 10% H3PO4 to adjust the pH value of the sealing solution to 3 to 4.

5. The calcium phosphate sealing treatment method based on the micro-arc oxidation coating of biomedical magnesium alloy according to claim 1, characterized in that, The immersion time of the micro-arc oxidation treated coating in the sealing solution is 10 min to 30 min.

6. The calcium phosphate sealing treatment method based on the micro-arc oxidation coating of biomedical magnesium alloy according to claim 1, characterized in that, The electrolyte is an aqueous mixed solution of Na2SiO3·9H2O, KF·2H2O, and NaOH.

7. The calcium phosphate sealing treatment method based on the micro-arc oxidation coating of biomedical magnesium alloy according to claim 6, characterized in that, In the electrolyte, the dosage ratio of Na2SiO3·9H2O, KF·2H2O, NaOH to water is 20 g to 25 g: 7 g to 8 g: 8 g to 10 g: 1 L.

8. The calcium phosphate sealing treatment method based on the micro-arc oxidation coating of biomedical magnesium alloy according to claim 1, wherein, The micro-arc oxidation process parameters are as follows: voltage 0 - 450V, current density 3A / cm 2 ~5A / cm 2 , pulse frequency 100Hz - 500Hz, duty cycle -30% - 30%.

9. The calcium phosphate sealing treatment method based on the micro-arc oxidation coating of biomedical magnesium alloy according to claim 1, characterized in that, The micro-arc oxidation treatment time is 30 min to 35 min.

10. The calcium phosphate sealing treatment method based on the micro-arc oxidation coating of biomedical magnesium alloy according to claim 1, wherein, The magnesium alloy is Mg-0.45Zn-0.45Ca alloy.

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