CN105568339A - Magnesium/magnesium alloy matrix multi-coating composite and preparation method thereof - Google Patents

Abstract

The invention discloses a magnesium/magnesium alloy matrix multi-coating composite and a preparation method thereof. The multi-coating composite comprises a magnesium/magnesium alloy matrix, a micro-arc oxidation coating formed on the magnesium/magnesium alloy matrix and a zinc stearate coating formed on the micro-arc oxidation coating; the thickness of the micro-arc oxidation coating is 3.9-4.7 microns; the thickness of the zinc stearate coating is 15.1-16.3 microns. The preparation method includes three steps of pretreatment, micro-arc oxidation and electrodeposition of the zinc stearate coating. The preparation process is simple to operate, easy for control and high in yield, the thickness of each composite layer is easy to control, and the prepared composite has the advantages of superhydrophobicity, excellent corrosion resistance and the like.

Description

A kind of multi-coating composite material with magnesium/magnesium alloy as matrix and preparation method thereof

technical field

The invention relates to a composite coating material and a preparation method thereof, in particular to an electrodeposited modified micro-arc oxidation composite coating material with a magnesium/magnesium alloy as a matrix and a preparation method thereof.

Background technique

As an emerging metal structure material, magnesium alloy is used in industrial applications, such as automobile, electronics, aerospace, national defense, metallurgy, chemical industry, transportation and other fields, which have important application value and broad application prospects. It is due to its good cutting performance, thermoforming performance, thermal conductivity, vibration absorption performance and damping performance. However, due to the active chemical properties of magnesium itself, the standard electrode potential is very low, so that magnesium alloys are extremely vulnerable to corrosion, which causes a series of problems. Therefore, when magnesium or magnesium alloy industrial materials are used, their anticorrosion treatment is one of the technical problems that need to be solved first.

In the prior art, there are three ways to improve the corrosion resistance of magnesium alloys: alloying, processing and surface modification. Among them, through the improvement of the manufacturing process, the corrosion resistance of magnesium alloys can also be improved to a certain extent. The corrosion performance is better improved. However, due to the very active chemical properties of magnesium alloys, the corrosion resistance of magnesium alloys cannot be completely solved only by improving the processing technology.

In recent years, surface modification has become the most commonly used main technical means in the prior art. In order to achieve sufficient protection properties, superhydrophobic coatings are favored by everyone. Moreover, magnesium alloy, as a metal structure material, especially needs to design a new coating with excellent corrosion resistance from the integration of coating structure and function. Up to now, people have researched a variety of surface modification coatings and surface modification technologies, and developed a large number of products. However, the surface-modified magnesium alloy products produced by the prior art all have many deficiencies, mainly in the comprehensive performance indicators such as corrosion resistance, bonding force, and durability. Not particularly ideal. Other surface modification methods of magnesium alloys, such as chemical conversion coating, ion implantation, vapor deposition, polymer coating, etc., generally have shortcomings or problems such as small improvement in corrosion resistance and poor wear resistance and durability.

Contents of the invention

Based on the above technical problems, the present invention provides a multi-coat composite material with magnesium/magnesium alloy as the matrix, and a preparation method of the composite material.

The technical solution adopted in the present invention is:

A multi-coat composite material based on magnesium/magnesium alloy, including magnesium/magnesium alloy substrate, micro-arc oxidation coating formed on the magnesium/magnesium alloy substrate, and stearin formed on the micro-arc oxidation coating Zinc acid coating; the thickness of the micro-arc oxidation coating is 3.9-4.7 μm; the thickness of the zinc stearate coating is 15.1-16.3 μm.

Above-mentioned zinc stearate coating is superhydrophobic coating.

Preferably, the above-mentioned multi-coated composite material based on magnesium/magnesium alloy has a lamellar structure.

The electrodeposition-modified micro-arc oxidation composite coating material with the above-mentioned structural form based on magnesium/magnesium alloy has a dense structure and strong adhesion, excellent corrosion resistance and long service life.

The above-mentioned preparation method of the multi-coated composite material with magnesium/magnesium alloy as the matrix comprises the following steps:

a Pretreatment step: Grinding the magnesium/magnesium alloy blank until there are no obvious scratches on the surface, then cleaning it with organic solvent and/or deionized water, drying it with wind for later use;

b micro-arc oxidation step: at room temperature, a mixed solution of phytic acid and sodium hydroxide is used as the electrolyte, the pretreated magnesium/magnesium alloy billet is used as the anode, and the magnesium rod is used as the cathode to construct a closed two-electrode system; The concentration of acid is 8g/L, the concentration of sodium hydroxide is 10g/L;

Micro-arc oxidation is divided into four stages:

One is the anodic oxidation stage: the voltage of the closed two-electrode system is controlled between 100-120V, and the time is controlled within 3-4s;

The second is the spark discharge stage: slowly increase the voltage until it is adjusted to 240-260V, and the voltage adjustment time is controlled at 10-12min;

The third is the micro-arc oxidation stage: the voltage is kept between 240-260V, and the time is controlled at 3-5min;

The fourth is the arc extinguishing stage: the voltage is kept between 240-260V, until the spark finally disappears, and the popping sound stops;

After the micro-arc oxidation is completed, a micro-arc oxidation coating is formed on the magnesium/magnesium alloy, take it out, rinse it with deionized water, and dry it with the wind; put it in an oven, and dry it at a constant temperature at 80-120 ° C for 2- 3h;

C zinc stearate electrodeposition step: under room temperature, with zinc stearate solution as electrolyte, the magnesium/magnesium alloy after micro-arc oxidation is as negative pole, and platinum electrode is as positive pole, builds closed two electrode system; Zinc stearate solution It is prepared by first adding 0.1mol stearic acid and then adding 0.05mol zinc nitrate to 1L organic solvent;

Adjust the voltage to 25V, and control the deposition time to 50-70min. After the deposition is completed, a zinc stearate coating is formed on the micro-arc oxidation coating. Take it out, rinse it with deionized water, and dry it with wind; place it in an oven , at 80-120 ° C, constant temperature drying treatment 2-3h, that is.

The technical effect directly brought by the above method is that under a certain current density, the formation rate of the oxide film is higher than the dissolution rate, and the formed micro-arc oxidation film has good bonding force, strength, corrosion resistance and certain self-healing ability ; The zinc stearate coating prepared by electrodeposition can be well combined with the inner micro-arc oxidation coating through the action of electric current, and its superhydrophobic performance can effectively block various ions and water molecules in the external environment Corrosion of magnesium/magnesium alloys through micropores in microarc oxidation coatings.

That is, in the above technical solution, a micro-arc oxidation coating with good bonding force, strength, corrosion resistance and certain self-healing ability is used as the transition layer; then on the basis of the transition layer, a layer of superhydrophobic Zinc stearate coating to obtain electrodeposited modified micro-arc oxidation composite coating material based on magnesium/magnesium alloy. This effectively ensures the compactness and good corrosion resistance of the composite coating.

In addition, in the above method, the deposition time of each assembly is controlled to 50-70min. The main consideration is that the microgalvanic corrosion on the surface of the magnesium alloy will occur if the magnesium alloy is in the electrodeposition system for a long time, and the deposited stearin will be damaged if the time is too short. Zinc acid coating is unevenly distributed on the surface; the deposition voltage of electrodeposition is limited to 25V, because the magnesium alloy deposition voltage is too high, that is, the current density is too high to cause the cracking or peeling of the zinc stearate coating, and the current density is too high. A small value will cause the film thickness to be too thin and uneven.

The core technical idea of the above-mentioned technical solution is to use electrodeposition technology to realize the close combination of superhydrophobic zinc stearate and micro-arc oxidation coating, so as to effectively seal the Microporosity of arc oxidation coating. Therefore, this surface modification method, on the one hand, is technically simpler, more convenient and quicker, and easier to control; it is also low in cost, environmentally friendly and pollution-free, and has a high yield. On the other hand, the prepared electrodeposition-modified micro-arc oxidation composite coating material based on magnesium/magnesium alloy has excellent superhydrophobic and corrosion resistance properties.

In addition, the preparation of zinc stearate superhydrophobic coating can provide a low-cost, high-efficiency surface modification method to improve the corrosion resistance of magnesium alloys.

Preferably, the grinding of the above-mentioned magnesium/magnesium alloy billet is first performed with a grinding wheel or coarse sandpaper for rough grinding, and then with 1500-mesh silicon carbide sandpaper for fine grinding.

The technical effect directly brought by this optimal technical solution is that the operation is simple, and the surface finish and roughness of the substrate are good, which is conducive to better film formation in the micro-arc oxidation process, so as to ensure the uniformity and compactness of the film formation.

In step c: the zinc stearate solution is prepared by first adding 0.1 mol of stearic acid and then 0.05 mol of zinc nitrate into 1 L of organic solvent; preferably, the organic solvent is ethanol or acetone.

The technical effect directly brought by this technical solution is that the zinc nitrate presents the state of zinc ions in a short period of time, and can be effectively deposited on the surface of the sample used as the negative electrode. As the reaction process proceeds, zinc nitrate further reacts with stearic acid to form a superhydrophobic zinc stearate coating.

In summary, compared with the prior art, the present invention has the following beneficial effects:

1. The electrodeposition-modified micro-arc oxidation composite coating material based on magnesium/magnesium alloy prepared by the present invention has good film-forming performance, uniform structure, excellent corrosion resistance, and good super-hydrophobic effect.

2. The preparation process of the present invention is simple, easy to control, high yield, short preparation cycle and low manufacturing cost.

Description of drawings

Fig. 1 is the scanning electron micrograph (magnification is 20000 times) of the micro-arc oxidation composite coating that the electrodeposition modification of matrix is made with the magnesium alloy Mg-4Li-1Ca that embodiment 1 makes;

Fig. 2 is the contact angle figure of the micro-arc oxidation composite coating of the electrodeposition modification of substrate that is made in embodiment 1 with magnesium alloy Mg-4Li-1Ca;

Fig. 3 is the contrast dynamics of the micro-arc oxidation composite coating and the magnesium alloy Mg-4Li-1Ca substrate without coating obtained by the embodiment 1 with the magnesium alloy Mg-4Li-1Ca as the electrodeposition modification of the matrix. Potential polarization curve diagram;

Fig. 4-1 is the impedance curve of the micro-arc oxidation composite coating of the electrodeposition modification of matrix that is obtained in embodiment 1 with magnesium alloy Mg-4Li-1Ca;

Figure 4-2 is the impedance curve of the magnesium alloy Mg-4Li-1Ca substrate without coating;

Fig. 5 is the comparison immersion of the electrodeposited modified micro-arc oxidation composite coating and the magnesium alloy Mg-4Li-1Ca substrate without coating obtained in Example 1 Hydrogen evolution rate curve.

Fig. 6 is a cross-sectional scanning electron micrograph (magnification: 5000 times) of the electrodeposited modified micro-arc oxidation composite coating prepared in Example 1 based on the magnesium alloy Mg-4Li-1Ca.

detailed description

The invention provides a multi-coated composite material with a magnesium/magnesium alloy as a substrate, which has a lamellar structure, including a magnesium/magnesium alloy substrate, a micro-arc oxidation coating formed on the magnesium/magnesium alloy substrate, and A zinc stearate coating formed on the micro-arc oxidation coating; the thickness of the micro-arc oxidation coating is 3.9-4.7 μm; the thickness of the zinc stearate coating is 15.1-16.3 μm. The zinc stearate coating is a superhydrophobic coating.

The preparation method of the present invention will be described in detail below in conjunction with the accompanying drawings and specific examples.

Example 1

The base material is magnesium alloy Mg-4Li-1Ca, and the preparation method is as follows:

a Pretreatment step: Grinding the magnesium alloy Mg-4Li-1Ca billet until there is no obvious scratch on the surface, then cleaning it with deionized water, drying it with wind for later use. The specific grinding process is to use a grinding wheel or coarse sandpaper for rough grinding, and then use 1500 mesh silicon carbide sandpaper for fine grinding.

b Micro-arc oxidation step: at room temperature, a mixed solution of phytic acid and sodium hydroxide is used as the electrolyte, the pretreated magnesium/magnesium alloy billet is used as the anode, and the magnesium rod is used as the cathode to construct a closed two-electrode system. The concentration of phytic acid in the mixed solution is 8g/L, and the concentration of sodium hydroxide is 10g/L. The specific preparation method of the mixed solution is as follows: firstly add 8 g of phytic acid into 1 L of distilled water, and then add 10 g of sodium hydroxide to obtain the mixture.

Micro-arc oxidation is divided into four stages:

One is the anodizing stage: the voltage of the closed two-electrode system is controlled at 100V, and the time is controlled at 3s;

The second is the spark discharge stage: slowly increase the voltage until it is adjusted to 260V, and the voltage adjustment time is controlled within 10-12min;

The third is the stage of micro-arc oxidation and arc extinction: the voltage is kept at 260V until the spark finally disappears and the beeping sound stops.

After the micro-arc oxidation is completed, a micro-arc oxidation coating is formed on the magnesium/magnesium alloy, which is taken out, rinsed with deionized water, and dried with wind; placed in an oven, and dried at a constant temperature for 3 hours at 120°C.

C zinc stearate electrodeposition step: under room temperature, with zinc stearate solution as electrolyte, the magnesium/magnesium alloy after micro-arc oxidation is as negative pole, and platinum electrode is as positive pole, builds closed two electrode system; Zinc stearate solution It is prepared by first adding 0.1mol stearic acid to 1L ethanol and then adding 0.05mol zinc nitrate.

Adjust the voltage to 25V, and control the deposition time to 50min. After the deposition is completed, a zinc stearate coating is formed on the micro-arc oxidation coating. Take it out, rinse it with deionized water, and dry it with wind; place it in an oven, At 120°C, dry at a constant temperature for 2 hours to obtain the product.

Example 2

The base material is magnesium alloy AZ31, and the rest are the same as in Example 1.

Example 3

The base material is magnesium, and the rest are the same as in Example 1.

Example 4

The base material is Mg-1Li-Ca alloy, and the rest are the same as in Example 1.

Example 5

The base material is magnesium alloy Mg-4Li-1Ca, and the preparation method is as follows:

a Pretreatment step: Grinding the magnesium alloy Mg-4Li-1Ca billet until there is no obvious scratch on the surface, then cleaning it with deionized water, drying it with wind for later use. The specific grinding process is to use a grinding wheel or coarse sandpaper for rough grinding, and then use 1500 mesh silicon carbide sandpaper for fine grinding.

b Micro-arc oxidation step: at room temperature, a mixed solution of phytic acid and sodium hydroxide is used as the electrolyte, the pretreated magnesium/magnesium alloy billet is used as the anode, and the magnesium rod is used as the cathode to construct a closed two-electrode system. The concentration of phytic acid in the mixed solution is 8g/L, and the concentration of sodium hydroxide is 10g/L. The specific preparation method of the mixed solution is as follows: firstly add 8 g of phytic acid into 1 L of distilled water, and then add 10 g of sodium hydroxide to obtain the mixture.

Micro-arc oxidation is divided into four stages:

One is the anodic oxidation stage: the voltage of the closed two-electrode system is controlled at 120V, and the time is controlled at 4s;

The second is the spark discharge stage: slowly increase the voltage until it is adjusted to 240V, and the voltage adjustment time is controlled within 10-12min;

The third is the stage of micro-arc oxidation and arc extinguishing: the voltage is kept at 240V until the spark finally disappears and the knocking sound stops.

After the micro-arc oxidation is completed, a micro-arc oxidation coating is formed on the magnesium/magnesium alloy, which is taken out, rinsed with deionized water, and dried with wind; placed in an oven, and dried at a constant temperature for 3 hours at 100°C.

C zinc stearate electrodeposition step: under room temperature, with zinc stearate solution as electrolyte, the magnesium/magnesium alloy after micro-arc oxidation is as negative pole, and platinum electrode is as positive pole, builds closed two electrode system; Zinc stearate solution It is prepared by first adding 0.1mol stearic acid to 1L ethanol and then adding 0.05mol zinc nitrate.

Adjust the voltage to 25V, and control the deposition time to 70min. After the deposition is completed, a zinc stearate coating is formed on the micro-arc oxidation coating. Take it out, rinse it with deionized water, and dry it with the wind; place it in an oven, Dry at 100°C for 2 hours at a constant temperature to obtain the product.

Example 6

The base material is magnesium alloy Mg-4Li-1Ca, and the preparation method is as follows:

a Pretreatment step: Grinding the magnesium alloy Mg-4Li-1Ca billet until there is no obvious scratch on the surface, then cleaning it with deionized water, drying it with wind for later use. The specific grinding process is to use a grinding wheel or coarse sandpaper for rough grinding, and then use 1500 mesh silicon carbide sandpaper for fine grinding.

b Micro-arc oxidation step: at room temperature, a mixed solution of phytic acid and sodium hydroxide is used as the electrolyte, the pretreated magnesium/magnesium alloy billet is used as the anode, and the magnesium rod is used as the cathode to construct a closed two-electrode system. The concentration of phytic acid in the mixed solution is 8g/L, and the concentration of sodium hydroxide is 10g/L. The specific preparation method of the mixed solution is as follows: firstly add 8 g of phytic acid into 1 L of distilled water, and then add 10 g of sodium hydroxide to obtain the mixture.

Micro-arc oxidation is divided into four stages:

One is the anodizing stage: the voltage of the closed two-electrode system is controlled at 110V, and the time is controlled at 4s;

The second is the spark discharge stage: slowly increase the voltage until it is adjusted to 250V, and the voltage adjustment time is controlled within 10-12min;

The third is the stage of micro-arc oxidation and arc extinguishing: the voltage is kept at 250V until the spark finally disappears and the popping sound stops.

After the micro-arc oxidation is completed, a micro-arc oxidation coating is formed on the magnesium/magnesium alloy, which is taken out, rinsed with deionized water, and dried with wind; placed in an oven, and dried at a constant temperature for 3 hours at 80°C.

C zinc stearate electrodeposition step: under room temperature, with zinc stearate solution as electrolyte, the magnesium/magnesium alloy after micro-arc oxidation is as negative pole, and platinum electrode is as positive pole, builds closed two electrode system; Zinc stearate solution It is prepared by first adding 0.1mol stearic acid to 1L ethanol and then adding 0.05mol zinc nitrate.

Adjust the voltage to 25V, and control the deposition time to 60min. After the deposition is completed, a zinc stearate coating is formed on the micro-arc oxidation coating. Take it out, rinse it with deionized water, and dry it with wind; place it in an oven, Dry at 100°C for 2 hours at a constant temperature to obtain the product.

Example 7

The base material is magnesium alloy Mg-4Li-1Ca, and the preparation method is as follows:

a Pretreatment step: Grinding the magnesium alloy Mg-4Li-1Ca billet until there is no obvious scratch on the surface, then cleaning it with deionized water, drying it with wind for later use. The specific grinding process is to use a grinding wheel or coarse sandpaper for rough grinding, and then use 1500 mesh silicon carbide sandpaper for fine grinding.

b Micro-arc oxidation step: at room temperature, a mixed solution of phytic acid and sodium hydroxide is used as the electrolyte, the pretreated magnesium/magnesium alloy billet is used as the anode, and the magnesium rod is used as the cathode to construct a closed two-electrode system. The concentration of phytic acid in the mixed solution is 8g/L, and the concentration of sodium hydroxide is 10g/L. The specific preparation method of the mixed solution is as follows: firstly add 8 g of phytic acid into 1 L of distilled water, and then add 10 g of sodium hydroxide to obtain the mixture.

Micro-arc oxidation is divided into four stages:

One is the anodic oxidation stage: the voltage of the closed two-electrode system is controlled at 105V, and the time is controlled at 3s;

The second is the spark discharge stage: slowly increase the voltage until it is adjusted to 260V, and the voltage adjustment time is controlled within 10-12min;

The third is the stage of micro-arc oxidation and arc extinction: the voltage is kept at 260V until the spark finally disappears and the beeping sound stops.

After the micro-arc oxidation is completed, a micro-arc oxidation coating is formed on the magnesium/magnesium alloy, which is taken out, rinsed with deionized water, and dried with wind; placed in an oven, and dried at a constant temperature for 3 hours at 100°C.

C zinc stearate electrodeposition step: under room temperature, with zinc stearate solution as electrolyte, the magnesium/magnesium alloy after micro-arc oxidation is as negative pole, and platinum electrode is as positive pole, builds closed two electrode system; Zinc stearate solution It is prepared by first adding 0.1mol stearic acid to 1L ethanol and then adding 0.05mol zinc nitrate.

Adjust the voltage to 25V, and control the deposition time to 65min. After the deposition is completed, a zinc stearate coating is formed on the micro-arc oxidation coating. Take it out, rinse it with deionized water, and dry it with wind; place it in an oven, At 80°C, dry at a constant temperature for 3 hours to obtain the product.

Select Example 1 as a representative example, and carry out the magnification of 20,000 times observation under the scanning electron microscope, contact angle, electrochemical test analysis, immersion in 3.5% NaCl solution for 85h, and carry out hydrogen evolution test analysis or Comparative analysis, the results are shown in Figure 1 to Figure 6.

Fig. 1 is the scanning electron micrograph (magnification: 20000 times) of the electrodeposited modified micro-arc oxidation composite coating with the magnesium alloy Mg-4Li-1Ca as the substrate obtained in Example 1. As shown in Figure 1, it can be seen that the coating presents a uniform lamellar structure and spreads evenly.

Fig. 2 is the contact angle diagram of the electrodeposition-modified micro-arc oxidation composite coating with the magnesium alloy Mg-4Li-1Ca as the substrate prepared in Example 1. As shown in Figure 2, the contact angle of the zinc stearate coating is 153.5°, showing a superhydrophobic coating.

Fig. 3 is the contrast dynamics of the micro-arc oxidation composite coating and the magnesium alloy Mg-4Li-1Ca substrate without coating obtained by the embodiment 1 with the magnesium alloy Mg-4Li-1Ca as the electrodeposition modification of the matrix. Potential polarization graph.

As shown in Figure 3, the comparison results show that the self-corrosion current density of the multi-coated composite material based on magnesium alloy is significantly lower than that of the magnesium alloy without coating (from 3.55×10 ^-5 A/cm ² down to 7.68×10 ^-8 A/cm ² ). The results show that, compared with the uncoated magnesium alloy Mg-4Li-1Ca, the magnesium alloy covered with electrodeposited modified micro-arc oxidation composite coating has excellent corrosion resistance.

Figure 4-1 is the impedance curve of the micro-arc oxidation composite coating prepared by electrodeposition modification using the magnesium alloy Mg-4Li-1Ca as the substrate in Example 1; Figure 4-2 is the magnesium alloy without coating Impedance curves of Mg-4Li-1Ca substrate. As shown in Figure 4-1 and Figure 4-2, it can be seen from the comparison results that the electrodeposited modified micro-arc oxidation composite coating based on magnesium alloy Mg-4Li-1Ca and the magnesium alloy Mg without coating Compared with -4Li-1Ca, the AC impedance arc is obviously increased. The results show that, compared with the uncoated magnesium alloy Mg-4Li-1Ca, the magnesium alloy covered with electrodeposited modified micro-arc oxidation composite coating has excellent corrosion resistance.

Fig. 5 is the comparative immersion hydrogen evolution rate of the electrodeposition-modified micro-arc oxidation composite coating and the magnesium alloy Mg-4Li-1Ca without coating prepared in Example 1 curve. As shown in Figure 5, the comparison results can be seen that the electrodeposition modified micro-arc oxidation composite coating based on the magnesium alloy Mg-4Li-1Ca is compared with the magnesium alloy Mg-4Li-1Ca without coating. After soaking in 3.5% NaCl solution for 85h, the hydrogen evolution rate of the electrodeposition-modified micro-arc oxidation composite coating based on magnesium alloy Mg-4Li-1Ca decreased significantly (the hydrogen evolution rate was close to 0).

Fig. 6 is a cross-sectional scanning electron micrograph (magnification: 5000 times) of the electrodeposited modified micro-arc oxidation composite coating prepared in Example 1 based on the magnesium alloy Mg-4Li-1Ca. As shown in Figure 6, the bright strip part in the figure is the thickness of the micro-arc oxidation coating, and the brighter strip part above is the thickness of the zinc stearate coating. It can be seen from the figure that the micro-arc oxidation coating The thickness of the layer is 3.9-4.7 μm, the thickness of the zinc stearate coating is 15.1-16.3 μm, the total thickness of the above coatings is 19-21 μm.

Examples 2-4 were subjected to scanning electron microscope magnification of 20,000 times observation, contact angle, electrochemical test analysis, hydrogen evolution test analysis after soaking in 3.5% NaCl solution for 85 hours, and the obtained results were basically consistent with those of Example 1. It shows that the matrix material of the present invention can be selected from magnesium or various types of magnesium alloys.

Claims (4)

1. a kind of multi-coating composite material taking magnesium/magnesium alloy as matrix, is characterized in that: comprise magnesium/magnesium alloy matrix, be formed on the micro-arc oxidation coating on magnesium/magnesium alloy matrix, and be formed in micro-arc oxidation Zinc stearate coating on the coating; the thickness of the micro-arc oxidation coating is 3.9-4.7 μm; the thickness of the zinc stearate coating is 15.1-16.3 μm. 2. a kind of as claimed in claim 1 is the preparation method of the multi-coat composite material of matrix with magnesium/magnesium alloy, it is characterized in that comprising the following steps: a Pretreatment step: Grinding the magnesium/magnesium alloy blank until there are no obvious scratches on the surface, then cleaning it with organic solvent and/or deionized water, drying it with wind for later use; b micro-arc oxidation step: at room temperature, a mixed solution of phytic acid and sodium hydroxide is used as the electrolyte, the pretreated magnesium/magnesium alloy billet is used as the anode, and the magnesium rod is used as the cathode to construct a closed two-electrode system; The concentration of acid is 8g/L, the concentration of sodium hydroxide is 10g/L; Micro-arc oxidation is divided into four stages: One is the anodic oxidation stage: the voltage of the closed two-electrode system is controlled between 100-120V, and the time is controlled within 3-4s; The second is the spark discharge stage: slowly increase the voltage until it is adjusted to 240-260V, and the voltage adjustment time is controlled at 10-12min; The third is the micro-arc oxidation stage: the voltage is kept between 240-260V, and the time is controlled at 3-5min; The fourth is the arc extinguishing stage: the voltage is kept between 240-260V, until the spark finally disappears, and the popping sound stops; After the micro-arc oxidation is completed, a micro-arc oxidation coating is formed on the magnesium/magnesium alloy, take it out, rinse it with deionized water, and dry it with the wind; put it in an oven, and dry it at a constant temperature at 80-120 ° C for 2- 3h; C zinc stearate electrodeposition step: under room temperature, with zinc stearate solution as electrolyte, the magnesium/magnesium alloy after micro-arc oxidation is as negative pole, and platinum electrode is as positive pole, builds closed two electrode system; Zinc stearate solution It is prepared by first adding 0.1mol stearic acid and then adding 0.05mol zinc nitrate to 1L organic solvent; Adjust the voltage to 25V, and control the deposition time to 50-70min. After the deposition is completed, a zinc stearate coating is formed on the micro-arc oxidation coating. Take it out, rinse it with deionized water, and dry it with wind; place it in an oven , at 80-120 ° C, constant temperature drying treatment 2-3h, that is. 3. a kind of preparation method that takes magnesium/magnesium alloy as matrix multi-coat composite material according to claim 2, is characterized in that, in the step a: the grinding of described magnesium/magnesium alloy blank is to adopt emery wheel or Coarse sandpaper for rough grinding, and then use 1500 mesh silicon carbide sandpaper for fine grinding. 4. A method for preparing a multi-coated composite material based on magnesium/magnesium alloy according to claim 2, characterized in that, in step c: the organic solvent is ethanol or acetone.