阅读说明：本技术 一种具备防护涂层镁合金及其制备方法和应用 (Magnesium alloy with protective coating and preparation method and application thereof ) 是由 邱于兵 罗维 齐锴 于 2021-08-16 设计创作，主要内容包括：本发明属于镁合金防腐蚀技术领域,具体涉及一种具备防护涂层镁合金及其制备方法和应用。本发明制备方法包括以下步骤：(1)将镁合金预处理后电镀金属锌获得具备镀锌层的镁合金；(2)在具备镀锌层的镁合金表面采用电化学法生长获得生物相容高分子层,即可获得具备防护涂层镁合金。本发明在镁合金的基础上先电镀一层金属层,然后使用电化学方法制备一层高分子层,涂层致密均匀,阻隔了外界溶液与镁合金基体的接触,大大提高了镁合金的稳定性和耐蚀能力。(The invention belongs to the technical field of magnesium alloy corrosion prevention, and particularly relates to a magnesium alloy with a protective coating, and a preparation method and application thereof. The preparation method comprises the following steps: (1) after magnesium alloy is pretreated, metal zinc is electroplated to obtain magnesium alloy with a zinc coating; (2) and (3) growing a biocompatible polymer layer on the surface of the magnesium alloy with the zinc coating by adopting an electrochemical method to obtain the magnesium alloy with the protective coating. According to the invention, a metal layer is electroplated on the basis of the magnesium alloy, and then a macromolecule layer is prepared by using an electrochemical method, so that the coating is compact and uniform, the contact between an external solution and a magnesium alloy matrix is blocked, and the stability and the corrosion resistance of the magnesium alloy are greatly improved.)

1. A preparation method of a magnesium alloy with a protective coating is characterized by comprising the following steps:

(1) electroplating metal zinc on the magnesium alloy to obtain the magnesium alloy with a zinc coating;

(2) and (3) growing a biocompatible polymer layer on the surface of the magnesium alloy with the zinc coating by adopting an electrochemical method to obtain the magnesium alloy with the protective coating.

2. The method according to claim 1, wherein the biocompatible polymer layer is one of polypyrrole, polyaniline, and polythiophene, preferably polypyrrole.

3. The preparation method according to claim 1, wherein the electrochemical method comprises using magnesium alloy with a zinc coating as a working electrode, saturated calomel as a reference electrode, a platinum sheet as a counter electrode, and a mixed solution of a monomer corresponding to a biocompatible polymer and an anion dopant as an electrolyte solution, wherein the temperature is 30-70 ℃, and the electricity consumption per square centimeter of the surface of the electrode is 5.5-9.5 ℃.

4. The preparation method according to claim 3, wherein the electrochemical method is carried out constant potential polarization, and the polarization potential is 1-3V; when the current density is less than 0.5mA/cm²Then, constant current polarization is adopted, and the polarization current density is 1-10mA/cm²When the current density is not less than 0.5mA/cm²Constant potential polarization is always used.

5. The preparation method according to claim 3, wherein the anionic dopant is anionic dopant A and/or anionic dopant B, and the anionic dopant A is one or more of sodium perchlorate, sodium p-toluenesulfonate, sodium tartrate and sodium dodecyl sulfate; the anion dopant B is one or more of sodium salicylate, dopamine, graphene and phytic acid.

6. The method according to claim 5, wherein the concentration of the corresponding monomer of the biocompatible macromolecule is 0.1-1mol/L, the concentration of the anionic dopant A is 0.1-0.5mol/L, and the concentration of B is 0.5-10 mmol/L.

7. The preparation method according to claim 1, wherein the electroplating is constant current electroplating by adopting a three-electrode system by putting magnesium alloy into an electroplating solution, the working electrode is magnesium alloy, the reference electrode is calomel, and the counter electrode is pure zinc;

preferably, the magnesium alloy is one of Mg-Al, Mg-RE and Mg-Zn magnesium alloys;

preferably, the electroplating solution comprises a metal salt and a buffer system, wherein the buffer system is a mixed solution of pyrophosphate and citrate; the metal salt comprises 0.1-0.4mol/L zinc salt, 0.2-0.6mol/L pyrophosphate and 0.05-0.2mol/L citrate.

8. The preparation method according to claim 1, wherein the step (1) further comprises pretreating the magnesium alloy before electroplating, wherein the pretreatment comprises sequentially performing alkali washing, acid washing, activating and zinc dipping on the magnesium alloy;

preferably, the alkaline washing solution used for alkaline washing is a mixed solution of 10-50g/L hydroxide and 5-20g/L carbonate;

preferably, the pickling solution used for pickling is a mixed solution of 5-20g/L of molybdate and 15-95g/L of phosphoric acid solution;

preferably, the activating solution used for activation is a 10-50 w% acid solution, and the acid is at least one of acetic acid, propionic acid, hydrofluoric acid and citric acid;

preferably, the zinc immersion liquid used for zinc immersion is a mixed liquid of 25-65g/L zinc salt, 100-150g/L pyrophosphate, 5-20g/L fluoride and 1-10g/L carbonate.

9. A magnesium alloy with a protective coating, characterized by being prepared according to the preparation method of any one of claims 1 to 8.

10. Use of the magnesium alloy protective coating according to claim 9 in the preparation of a human implant material.

Technical Field

The invention belongs to the technical field of magnesium alloy corrosion prevention, and particularly relates to a magnesium alloy with a protective coating, and a preparation method and application thereof.

Background

Magnesium alloys have been highly expected in the medical field because of their excellent biocompatibility, elastic modulus close to that of human bones, low density, and the like. However, because magnesium alloy is easy to corrode and degrade in human body and the degradation process can not be controlled, magnesium alloy is still in theoretical research stage as human implant material. From the literature reported so far, there are many methods for improving the corrosion resistance of magnesium alloys, such as high temperature doping and surface modification. However, the methods have the disadvantages of harsh reaction conditions, introduction of toxic and harmful substances, failure to achieve the practical application value and the like.

CN110512175A discloses a method for preparing Zn and ZnO coatings on the surface of magnesium alloy. The method comprises the specific steps that a Zn film is evaporated on the surface of the magnesium alloy in a vacuum state, and corrosion-resistant intermetallic compounds are generated at the interface of the magnesium alloy and the zinc film through annealing. Then the magnesium alloy is selectively oxidized, and partial alloy elements in the zinc and the magnesium alloy are diffused to the surface to generate oxidation reaction to generate an oxide film. The method is complex to operate and harsh in conditions, and industrial-scale mass production cannot be realized although the obtained coating is excellent in corrosion resistance. CN107955961B also discloses a method for improving corrosion resistance of magnesium alloy. The method specifically discloses that magnesium alloy is subjected to electro-oxidation treatment by chromate, and then the unoxidized part is packaged and protected by polytetrafluoroethylene. The method introduces toxic chromium ions and polytetrafluoroethylene which is incompatible with human body, and cannot be used as a human body implant material.

CN107740151A discloses a method for preparing a medical magnesium alloy surface active coating, which comprises the steps of pretreating the surface of a biomedical magnesium alloy, then depositing a hydroxyapatite active coating on the surface of the biomedical magnesium alloy by heating and electrifying in a closed reaction kettle by using the biomedical magnesium alloy as a substrate and adopting direct current. The technical scheme is that the hydroxyapatite coating is prepared on the surface of the biomedical magnesium alloy, and the hydroxyapatite coating can improve the degradation performance of the medical magnesium alloy so as to meet the application of the biomedical magnesium alloy in the aspect of medical implants, but the corrosion resistance is still to be improved.

Therefore, how to improve the corrosion resistance of magnesium alloy efficiently and harmlessly still is a big bottleneck that prevents the wide application of magnesium alloy in the medical field.

Disclosure of Invention

Aiming at the improvement requirement of the prior art, the invention provides a magnesium alloy with a protective coating, which aims to electroplate a metal layer on the basis of the magnesium alloy, then prepare a macromolecule layer by using an electrochemical method, have compact and uniform coating, block the contact between an external solution and a magnesium alloy matrix, greatly improve the stability and the corrosion resistance of the magnesium alloy and solve the technical problem of corrosion of the magnesium alloy.

In order to achieve the above object, according to one aspect of the present invention, there is provided a method for preparing a magnesium alloy with a protective coating, comprising the steps of:

(1) after magnesium alloy is pretreated, metal zinc is electroplated to obtain magnesium alloy with a zinc coating;

(2) growing on the surface of the magnesium alloy with the zinc coating by adopting an electrochemical method to obtain a biocompatible polymer layer, namely obtaining the magnesium alloy with the protective coating.

Preferably, the biocompatible polymer layer is one of polypyrrole, polyaniline and polythiophene, and is preferably polypyrrole.

Preferably, the electrochemical method is that magnesium alloy with a zinc coating layer is used as a working electrode, saturated calomel is used as a reference electrode, a platinum sheet is used as a counter electrode, a mixed solution of a corresponding monomer of a biocompatible macromolecule and an anion dopant is used as an electrolyte solution, the temperature is 30-70 ℃, and the electricity consumption per square centimeter of the surface of the electrode is 5.5-9.5 ℃.

Preferably, the electrochemical method is carried out constant potential polarization firstly, the polarization potential is 1-3V, and when the current density is less than 0.5mA/cm²Then, constant current polarization is adopted, and the polarization current density is 1-10mA/cm²If it is not less than 0.5mA/cm²Constant potential polarization is always used.

Preferably, the anion dopant is anion dopant A and/or anion dopant B, and the anion dopant A is one or more of sodium perchlorate, sodium p-toluenesulfonate, sodium tartrate and sodium dodecyl sulfate; the anion dopant B is one or more of sodium salicylate, dopamine, graphene and phytic acid.

Preferably, the concentration of the corresponding monomer of the biocompatible macromolecule is 0.1-1mol/L, the concentration of the anionic dopant A is 0.1-0.5mol/L, and the concentration of B is 0.5-10 mmol/L.

Preferably, the electroplating is constant current electroplating by putting the magnesium alloy into an electroplating solution and adopting a three-electrode system, wherein the working electrode is the magnesium alloy, the reference electrode is calomel, and the counter electrode is pure zinc;

preferably, the magnesium alloy is one of Mg-Al, Mg-RE and Mg-Zn magnesium alloys;

preferably, the electroplating solution comprises a metal salt and a buffer system, wherein the buffer system is a mixed solution of pyrophosphate and citrate; the metal salt comprises 0.1-0.4mol/L zinc salt, 0.2-0.6mol/L pyrophosphate and 0.05-0.2mol/L citrate.

Preferably, the step (1) further comprises the step of pretreating the magnesium alloy before electroplating, wherein the pretreatment comprises the steps of sequentially carrying out alkali washing, acid washing, activation and zinc dipping on the magnesium alloy;

preferably, the alkaline washing solution used for alkaline washing is a mixed solution of 10-50g/L hydroxide and 5-20g/L carbonate;

preferably, the pickling solution used for pickling is a mixed solution of 5-20g/L of molybdate and 15-95g/L of phosphoric acid solution;

preferably, the activating solution used for the activation is a 10-50 w% acid solution, and the acid is at least one of acetic acid, propionic acid, hydrofluoric acid and citric acid.

Preferably, the zinc immersion liquid used for zinc immersion is a mixed liquid of 25-65g/L zinc salt, 100-150g/L pyrophosphate, 5-20g/L fluoride and 1-10g/L carbonate.

According to another aspect of the invention, a magnesium alloy with a protective coating is provided, which is prepared according to the preparation method.

According to another aspect of the invention, the application of the magnesium alloy with the protective coating in preparing the human body implant material is provided.

The invention has the following beneficial effects:

(1) according to the invention, a metal layer is electroplated on the basis of the magnesium alloy, and then a macromolecule layer is prepared by using an electrochemical method, so that the coating is compact and uniform, the contact between an external solution and a magnesium alloy matrix is blocked, and the stability and the corrosion resistance of the magnesium alloy are greatly improved;

(2) the reagent used in the invention is nontoxic and harmless, the preparation condition is mild, the biocompatibility is good, the corrosion resistance of the magnesium alloy is obviously improved by the prepared coating, and the coating has wide application prospect in the aspect of slowing down the too fast degradation of the magnesium alloy implanted into a human body in the medical field.

Drawings

FIG. 1 is a hydrogen evolution test chart of example 1 and comparative examples 1 to 2;

FIG. 2 is an open circuit potential diagram of a graph showing the results of the electrochemical test in example 1;

FIG. 3 is an impedance plot of a plot of the results of the electrochemical test in example 1;

FIG. 4 is an open circuit potential diagram of a graph showing the results of the electrochemical test in example 2;

FIG. 5 is an impedance plot of a plot of the results of the electrochemical test in example 2;

FIG. 6 is an open circuit potential diagram of a graph showing the results of the electrochemical test in example 3;

FIG. 7 is an impedance plot of a plot of the results of the electrochemical tests in example 3;

FIG. 8 is an open circuit potential diagram of a graph showing the results of the electrochemical test in example 4;

FIG. 9 is an impedance diagram of a graph of the results of the electrochemical test in example 4.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Example 1

A magnesium alloy with a protective coating is prepared by the following method:

(1) the ZK60 magnesium alloy is firstly polished by sand paper, then sequentially washed by alkali, washed by acid, activated and soaked in zinc, and then is washed by deionized water for standby. The alkaline washing liquid used for alkaline washing is a mixed solution of 50g/L hydroxide and 20g/L carbonate; the pickling solution used for pickling is a mixed solution of 20g/L of molybdate and 95g/L of phosphoric acid; the activating solution used for activation is 50 w% acetic acid, and the zinc dipping solution used for zinc dipping is a mixed solution of 65g/L zinc salt, 150g/L pyrophosphate, 20g/L fluoride and 10g/L carbonate.

(2) Electroplating after pretreatment, specifically putting the pretreated magnesium alloy into a galvanizing solution at 30 ℃ and-10 mA/cm²The lower constant current is galvanized for 1h, and the counter electrode is 10 multiplied by 10mm²The electroplating solution is 0.1mol/L zinc nitrate, 0.2mol/L pyrophosphate, 0.05mol/L citrate, 1g/L vanillin and 2g/L phytic acid, and the electroplating solution is washed by deionized water after the electroplating is finished.

(3) The method comprises the steps of growing on the surface of a metal layer by adopting an electrochemical method to obtain a biocompatible polymer layer, specifically, putting a zinc-plated magnesium alloy into a pyrrole solution, taking the magnesium alloy with a zinc coating as a working electrode, taking saturated calomel as a reference electrode, taking a platinum sheet as a counter electrode, taking a mixed solution of pyrrole monomers and sodium perchlorate corresponding to biocompatible polymers as an electrolyte solution, controlling the temperature to be 30 ℃, controlling the electricity consumption per square centimeter of the surface of the electrode to be 7.5 ℃, and performing constant potential polarization at a polarization potential of 3V when the magnesium alloy is grown by adopting the electrochemical method, wherein when the current density is less than 0.5mA/cm²Then, constant current polarization is adopted, and the polarization current density is 10mA/cm²If it is not less than 0.5mA/cm²Constant potential polarization is always used. The concentration of the pyrrole solution is 0.1mol/L, and the concentration of the sodium perchlorate is 0.3 mol/L. After the growth is finished, washing the coating with deionized water, and drying the coating with cold air to obtain the magnesium alloy with the protective coating, which is recorded as PPy/Zn composite coating

Example 2

The electricity consumption per square centimeter of the electrode surface was 5.5C.

Example 3

The electricity consumption per square centimeter of the electrode surface was 9.5C.

Example 4

The difference between this example and example 1 is that an anionic dopant B dopamine is also added, and the concentration of the dopamine is 10 mmol/L.

Comparative example 1

This example is different from example 1 in that the ZK60 magnesium alloy was subjected to only pretreatment.

Comparative example 2

This example differs from example 1 in that the ZK60 magnesium alloy was pretreated and galvanized only, and no electrochemical growth was used to obtain a biocompatible polymer layer, designated as Zn/ZK 60.

Test examples

1. And (5) hydrogen evolution testing. The test methods are as follows: the prepared magnesium alloy with the protective coating is used as an electrode to be soaked in a human body simulation solution, and the temperature is kept at 37 ℃. And (3) inversely immersing a glass tube with one end sealed and the other end in a horn shape into the solution, filling SBF into the glass tube, enabling one end of the horn mouth to face the electrode, and collecting gas emitted from the surface of the electrode. The human body simulated liquid is changed every 7 days.

The test results are shown in fig. 1.

As can be seen from fig. 1, when the magnesium alloy sample of the PPy/Zn composite coating prepared in example 1 was immersed for 37 days, the hydrogen evolution amount was always 0, which indicates that the magnesium alloy did not corrode. Comparative example 1 and comparative example 2 begin to increase significantly in hydrogen evolution after about 4 days of soaking, indicating that the base magnesium alloy has significantly corroded. Obviously, the PPy/Zn composite coating obviously improves the corrosion resistance of the matrix magnesium alloy.

2. And (4) performing electrochemical test. The test methods are as follows: the prepared magnesium alloy with the protective coating is used as an electrode to be soaked in human body simulation liquid, the impedance and the open-circuit potential of the magnesium alloy are measured every 24 hours, and the human body simulation liquid is replaced every 7 days. The test results are shown in fig. 2-9.

FIG. 2 is an open circuit potential diagram of a graph showing the results of the electrochemical test in example 1.

As can be seen in FIG. 2, the open circuit at a capacity of 7.5C ppy reached a maximum at day 0, 0.11V, and a minimum at day 42 for the coating plateau, 0.34V. Then the coating is damaged, the magnesium substrate is exposed, and the open circuit rapidly drops to-1.46V, which is close to the open circuit (-1.5V) of the magnesium alloy.

FIG. 3 is an impedance diagram of a graph of the results of the electrochemical test in example 1.

As can be seen from FIG. 3, the impedance of a ppy with a charge of 7.5C does not reach a maximum at day 0 as with an open circuit, but is about 2.6X 10 at day 12⁴Ω·cm². This is because the impedance test affects the sample and requires a long soak time to stabilize. On day 43, the coating was broken and the impedance dropped rapidly to 3700. omega. cm²。

FIG. 4 is an open circuit potential diagram of a graph showing the results of the electrochemical test in example 2.

As can be seen in FIG. 4, the open circuit of ppy with a charge of 5.5C reached a maximum on day 9, 0.028V, and a minimum on day 6 for the plateau phase of the coating, 0.17V. This is not the same rule as the ppy of 7.5C, indicating that the stability of the coating is less excellent than the ppy of 7.5C. After the coating broke on day 32, the open circuit rapidly dropped to-1.48V, approaching that of the magnesium alloy.

FIG. 5 is an impedance diagram of a graph of the results of the electrochemical test in example 2.

As can be seen from FIG. 5, the resistance of ppy with a 5.5C charge continues to increase during the plateau phase until it reaches 1.8 × 10⁴Ω·cm². On day 31, the coating was broken and the impedance dropped rapidly to 2900. omega. cm²。

FIG. 6 is an open circuit potential diagram of a graph of the results of the electrochemical test in example 3.

As can be seen in fig. 6, the open circuit of ppy with a charge of 9.5C reached a maximum on day 6, -0.034V, and a minimum on day 18 for the stable phase of the coating, -0.12V. After which the coating broke and the open circuit dropped rapidly to-1.47V.

FIG. 7 is an impedance diagram of a graph of the results of the electrochemical test in example 3.

As can be seen from FIG. 7, the impedance of ppy with a capacity of 9.5C reached a maximum at day 18 of 8000. omega. cm². On day 19 the coating broke and the impedance dropped rapidly to 3000. omega. cm²。

FIG. 8 is an open circuit potential diagram of a graph showing the results of the electrochemical test in example 4.

As can be seen in fig. 8, the open circuit of sodium perchlorate-doped ppy reached a maximum on day 0, -0.082V, and a minimum on day 48 for the coating plateau, -0.28V. This is consistent with the data of fig. 2. On day 55 the coating broke and the open circuit dropped rapidly to-1.43V.

FIG. 9 is an impedance diagram of a graph of the results of the electrochemical test in example 4.

As can be seen from FIG. 9, the impedance of the sodium perchlorate-doped ppy strain reached a maximum at day 45, 4.8X 10⁴Ω·cm². On day 55, the coating was broken and the impedance dropped rapidly to 3100. omega. cm²。

As can be seen from FIGS. 2-9, the open circuit of the PPy coating is maintained to fluctuate between 0 and-0.4V before the coating is not damaged, and the impedance is maintained to be substantially 1 × 10⁴-5×10⁴Ω·cm². However, when the coating is damaged, the open circuit immediately drops to around-1.5V, and the impedance decreases accordingly. As can be seen from FIGS. 2-3, after 43 days the coating was damaged, the open circuit potential rapidly shifted negative to near the open circuit potential of the matrix magnesium alloy, and the impedance was significantly reduced. As can be seen from FIGS. 4 to 5, the coating was broken after 31 days. As can be seen from FIGS. 6 to 7, the coating was broken after 19 days.

2-9, the PPy/Zn composite coating with 7.5C has the longest stable time which can reach 43 days and 5.5C, and the stable time is 31 days and the worst stable time of 9.5C, which is 19 days. When the electric quantity is all 7.5C, another dopant B is added, and the stability time of the prepared PPy is further improved and can reach 54 days. Therefore, the optimal charge for synthesizing PPy in the above example is 7.5C, and the addition of another dopant B is beneficial to the corrosion resistance of PPy.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.