A zinc alloy coating for inhibiting corrosion and galvanic corrosion of magnesium alloys and its preparation method

Abstract

This invention discloses a zinc alloy coating for inhibiting magnesium alloy corrosion and galvanic corrosion, and its preparation method. The preparation method includes the following steps: preparing a zinc alloy molten plating solution, wherein the zinc alloy molten plating solution comprises metallic zinc, metallic aluminum, and metallic magnesium; preheating a magnesium alloy substrate; immersing the preheated magnesium alloy substrate into the zinc alloy molten plating solution for immersion plating, wherein the temperature of the zinc alloy molten plating solution is 350-380°C during the immersion plating process, and maintaining it in a protective atmosphere for 20-30 seconds before removing it or leaving it in the plating solution, and cooling it to obtain the zinc alloy coating for inhibiting magnesium alloy galvanic corrosion; or, pouring the zinc alloy molten plating solution at a temperature of 350-380°C onto the surface of the preheated magnesium alloy substrate, maintaining it in a protective atmosphere for 20-30 seconds, and cooling it to obtain the zinc alloy coating for inhibiting magnesium alloy galvanic corrosion. The magnesium alloy substrate of this invention does not undergo phase composition changes due to high temperature, thus improving corrosion resistance, especially galvanic corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of corrosion and galvanic corrosion protection technology for magnesium alloys, and particularly to a zinc alloy coating for inhibiting galvanic corrosion of magnesium alloys and its preparation method. Background Technology

[0002] Magnesium possesses many excellent properties, such as low density, high strength, and good thermal and electrical conductivity, making magnesium alloys promising for wide applications in aerospace, automotive manufacturing, and other fields. However, due to its reactive nature and inability to form a dense surface film (PB ratio = 0.81), magnesium is highly susceptible to corrosion. Galvanic corrosion, in particular, is unavoidable in practical engineering, and magnesium has the most negative standard electrode potential of all engineering metals (-2.37V). This means that in actual industrial applications, almost all metallic materials will accelerate magnesium corrosion upon contact through the galvanic effect. Galvanic corrosion of magnesium alloys can be considered one of the biggest challenges in the industrial application of magnesium.

[0003] To address the galvanic corrosion problem of magnesium alloys, numerous surface treatment methods have been developed to enhance the corrosion resistance of magnesium and magnesium alloys. These include micro-arc oxidation (MAO), physical vapor deposition (PVD), chemical vapor deposition (CVD), chemical conversion, electroplating, and organic coatings. However, the protective layers obtained by these methods are not metallurgically bonded to the underlying magnesium alloy, resulting in poor adhesion. In practical industrial applications, these layers often break due to scratches and pressure, leading to galvanic corrosion of the exposed magnesium substrate and the other cathode metals (small anodic / large cathodic galvanic corrosion). This results in severe anodic dissolution in the damaged area. Therefore, the aforementioned surface treatment methods are unlikely to effectively suppress galvanic corrosion of magnesium in practical engineering applications.

[0004] Metallurgical bonding coatings can be formed on the surface of magnesium alloys using the powder thermal diffusion method. However, due to the high reaction temperature (>400℃) and long reaction time (>2h) of the powder thermal diffusion method, the phase composition and structure of magnesium alloys often change, affecting the mechanical properties of magnesium alloys.

[0005] During hot dipping or casting, magnesium alloys undergo a diffusion reaction with molten metal to form an intermediate bonding layer, which can potentially result in a more robust alloy coating on the magnesium alloy surface. However, if the temperature is too high (>400℃) during this process, it can cause changes in the phase composition of the magnesium alloy substrate, adversely affecting the mechanical properties of the magnesium alloy. In some cases, excessive melting or severe hot corrosion may even lead to the destruction of the overall structure of the magnesium alloy.

[0006] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the present invention provides a zinc alloy coating for inhibiting corrosion and galvanic corrosion of magnesium alloys and its preparation method, thereby solving the problem that existing corrosion-resistant coating preparation methods are difficult to effectively inhibit corrosion and galvanic corrosion of magnesium alloy substrates without significantly affecting the microstructure or mechanical properties of the substrate.

[0008] The technical solutions adopted by the present invention to solve the above technical problems are as follows:

[0009] In a first aspect, the present invention provides a method for preparing a zinc alloy coating that inhibits electro-corrosion and galvanic corrosion of magnesium alloys, the method comprising the following steps:

[0010] A zinc alloy plating solution is prepared, wherein the zinc alloy plating solution comprises metallic zinc, metallic aluminum, and metallic magnesium;

[0011] Preheating treatment is applied to the magnesium alloy substrate;

[0012] In a protective atmosphere, a preheated magnesium alloy substrate is immersed in the zinc alloy molten plating solution for immersion plating. During the immersion plating process, the temperature of the zinc alloy plating solution is 350-380°C. The substrate is removed after immersion for 20-30 seconds and cooled, or the magnesium alloy substrate is left in the plating solution and cooled together with the plating solution to obtain the zinc alloy coating that inhibits galvanic corrosion of magnesium alloy.

[0013] Alternatively, the zinc alloy plating solution at a temperature of 350–380°C is poured onto the surface of a preheated magnesium alloy substrate in a protective atmosphere, held for 20–30 seconds for immersion plating, and then cooled to obtain the zinc alloy coating that inhibits magnesium alloy corrosion and galvanic corrosion.

[0014] Preferably, in the zinc alloy plating solution, the mass content of aluminum is 2% to 4%, the mass content of magnesium is 1% to 3%, and the mass ratio of magnesium to aluminum is 1 / 3 to 2 / 3.

[0015] Preferably, the step of preparing the zinc alloy plating solution is as follows: heating a zinc block to 550-600°C, then adding a magnesium block and an aluminum block to obtain the zinc alloy plating solution.

[0016] Preferably, the step of preparing the zinc alloy plating solution specifically involves: mixing zinc blocks, magnesium blocks, and aluminum blocks, and heating the mixture to 550–600°C to obtain the zinc alloy plating solution.

[0017] Preferably, the preheating treatment specifically involves heating the surface of the magnesium alloy substrate to 250–350°C and holding it for 20–30 seconds.

[0018] Preferably, the heating method is selected from one of electric furnace heating, flame heating, laser heating, electric arc heating, and friction heating.

[0019] Preferably, before preheating the magnesium alloy substrate, the process further includes cleaning, leveling, surface roughening, and / or annealing the magnesium alloy substrate.

[0020] In a second aspect, the present invention provides a zinc alloy coating for inhibiting magnesium alloy corrosion and galvanic corrosion, wherein the zinc alloy coating for inhibiting magnesium alloy corrosion and galvanic corrosion is prepared by the preparation method described above.

[0021] Preferably, the thickness of the zinc alloy coating is 200-2000 μm.

[0022] Preferably, the zinc alloy coating contains 2% to 4% aluminum by mass, 1% to 3% magnesium by mass, and the mass ratio of magnesium to aluminum is 1 / 3 to 2 / 3.

[0023] Beneficial effects:

[0024] This invention discloses a zinc alloy coating for inhibiting corrosion and galvanic corrosion of magnesium alloys and its preparation method. Using this method, a zinc alloy coating metallurgically bonded to the surface of magnesium alloys can be obtained. Compared to coatings obtained by non-metallurgical methods such as micro-arc oxidation (MAO), physical vapor deposition (PVD), chemical vapor deposition (CVD), chemical conversion, electroplating, and organic coatings, the zinc alloy coating obtained by the method of this invention is a good metallurgically diffused bonding layer with stronger adhesion and adjustable coating thickness. It is also low-cost and easy to operate. Compared to powder thermal diffusion methods and hot-dip and casting methods for zinc and aluminum alloys, the preparation method of this invention uses a temperature below 380℃ and a holding time of less than 10 minutes, effectively preventing phase composition changes in the magnesium alloy substrate due to high temperatures or excessive melting and reaction with the plating solution. Furthermore, the zinc alloy coating exhibits stronger corrosion resistance than pure zinc, with a corrosion potential of approximately -1.10V (vs. SCE) and a corrosion current on the order of 10. -6 A / cm 2 The galvanic current is significantly reduced; however, hot-dip and casting methods for tin alloys and bismuth alloys with lower process temperatures will produce Mg2Sn and Mg3Bi2 phases with extremely poor corrosion resistance and brittleness when directly cast or hot-diped, requiring other pretreatment methods, which are complex and costly. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the preparation process of a preferred embodiment of the present invention.

[0026] Figure 2 This is a SEM image of the cross-sectional microstructure of the zinc alloy clad magnesium alloy component prepared in Example 1 of the present invention.

[0027] Figure 3This is a cross-sectional EDS energy dispersive spectroscopy (EDS) scan of the zinc alloy-clad magnesium alloy component prepared in Example 1 of the present invention.

[0028] Figure 4 The graphs show the potentiodynamic polarization curves of zinc alloy clad magnesium alloy components, AZ91 magnesium alloy, WE43 magnesium alloy, and pure zinc prepared in Examples 1 and 2 of this invention.

[0029] Figure 5 The graphs show the changes in galvanic current over time for the zinc alloy clad magnesium alloy components, AZ91 magnesium alloy, and WE43 magnesium alloy prepared in Examples 1 and 2 of this invention, respectively, and the galvanic current of the galvanic couples composed of aluminum.

[0030] Figure 6 The graphs show the changes in galvanic current over time for the zinc alloy clad magnesium alloy components, AZ91 magnesium alloy, and WE43 magnesium alloy prepared in Examples 1 and 2 of this invention, respectively, and the galvanized Q235 steel sheet with scratch damage (the base steel at the scratch is exposed).

[0031] Figure 7 The graphs show the changes in galvanic current over time for the zinc alloy-clad magnesium alloy components, AZ91 magnesium alloy, and WE43 magnesium alloy prepared in Examples 1 and 2 of this invention, respectively, and the galvanic current of the galvanic couples composed of zinc. Figure 7 The right image is an enlarged view of the area marked at the bottom of the left image.

[0032] Figure 8 The images show the microstructure of the zinc alloy clad magnesium alloy component and the AZ91 magnesium alloy prepared in Example 1 of this invention.

[0033] Figure 9 The images show the microstructure of the zinc alloy clad magnesium alloy component and the WE43 magnesium alloy prepared in Example 2 of this invention. Detailed Implementation

[0034] This invention provides a zinc alloy coating for inhibiting corrosion and galvanic corrosion of magnesium alloys and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] This invention provides a method for preparing a zinc alloy coating that inhibits corrosion and galvanic corrosion of magnesium alloys, see [link to relevant documentation]. Figure 1 The preparation method includes the following steps:

[0036] A zinc alloy plating solution is prepared, wherein the zinc alloy plating solution comprises metallic zinc, metallic aluminum, and metallic magnesium;

[0037] Preheating treatment is applied to the magnesium alloy substrate;

[0038] The preheated magnesium alloy substrate is immersed in the zinc alloy plating solution for immersion plating. During the immersion plating process, the temperature of the zinc alloy plating solution is 350-380°C. The substrate is removed after immersion for 20-30 seconds and cooled to obtain the zinc alloy coating that inhibits galvanic corrosion of magnesium alloy.

[0039] Alternatively, the zinc alloy plating solution at a temperature of 350–380°C is poured onto the surface of a preheated magnesium alloy substrate, kept in a protective atmosphere for 20–30 seconds, and then cooled to obtain the zinc alloy coating that inhibits galvanic corrosion of the magnesium alloy.

[0040] In this embodiment of the invention, by adding metallic magnesium and metallic aluminum to the zinc alloy plating solution, the melting point of the zinc alloy is kept below 380°C. During the preparation process, high temperatures are avoided from altering the phase composition and mechanical properties of the base magnesium alloy. In this embodiment of the invention, the coating is formed through the fusion, thermal diffusion, and intermetallic reaction of the molten zinc alloy plating solution and the magnesium alloy base. This preparation method is not affected by the shape and size of the magnesium alloy base, and the formed zinc alloy coating has good adhesion to the magnesium alloy base. The corrosion resistance of the zinc alloy coating prepared in this embodiment of the invention is much higher than that of the magnesium alloy base, the corrosion potential is significantly positively shifted, and the polarization curve exhibits a certain degree of self-passivation, which can effectively suppress the galvanic corrosion of the magnesium alloy base.

[0041] In this embodiment of the invention, the zinc alloy coating obtained on the surface of the magnesium alloy has a three-layer structure consisting of a magnesium alloy substrate, a diffusion intermediate layer, and a surface zinc alloy coating. The diffusion intermediate layer is generated by the mutual diffusion and intermetallic reaction between the magnesium alloy substrate and the molten zinc alloy plating solution.

[0042] In some embodiments, after cooling, the fused zinc alloy plating layer is leveled on the surface of the magnesium alloy substrate. The leveling method includes, but is not limited to: (1) using the surface tension of the molten zinc alloy plating itself to naturally form a plating layer of a certain thickness and a smooth surface; (2) using special tools or media (such as air) to remove excess molten zinc alloy plating by mechanical means (such as scraping, wiping, blowing, etc.) to obtain the required thickness and surface plating layer; (3) obtaining the desired plating layer by combining (1) and (2).

[0043] In some embodiments, the zinc alloy plating solution contains 2% to 4% aluminum by mass, 1% to 3% magnesium by mass, and the mass ratio of magnesium to aluminum is 1 / 3 to 2 / 3.

[0044] The corrosion resistance of zinc alloy coatings is weakened by the microcouple effect between the phases in the alloy and enhanced by the corrosion products formed during the corrosion process. Therefore, low magnesium and aluminum content results in limited protection against corrosion products; conversely, excessively high content leads to an overly strong microcouple effect, also reducing corrosion resistance. When the added aluminum content is 2%–4% by mass, the magnesium content is 1%–3% by mass, and the magnesium-to-aluminum mass ratio is 1 / 3–2 / 3, a large-area zinc-aluminum-magnesium ternary eutectic phase can be formed, weakening the microcouple effect in the zinc alloy and simultaneously increasing the density and integrity of corrosion products on the zinc alloy coating surface, thus improving corrosion resistance. Conversely, excessive or insufficient amounts of either aluminum or magnesium will generate a large number of binary phases, leading to an enhanced microcouple effect and affecting the composition of corrosion products, thereby weakening the corrosion resistance of the zinc alloy coating.

[0045] This invention lowers the melting point of zinc alloys by adding appropriate amounts of aluminum and magnesium to the zinc alloy molten plating bath. With the addition of aluminum and magnesium, the melting point of the system initially decreases and then increases. The lower reaction temperature and pre-melted magnesium slow down the melting and reaction rates between the zinc alloy molten plating bath and the magnesium alloy substrate. This avoids the rapid formation of large amounts of intermetallic compounds between the magnesium substrate and the zinc alloy plating bath, which would cause a rapid exothermic reaction, and inhibits excessive melting of the magnesium substrate or damage to its microstructure.

[0046] In some preferred embodiments, the zinc alloy solution contains 3% aluminum and 2% magnesium by mass.

[0047] In some embodiments, the step of preparing the zinc alloy plating solution specifically involves heating a zinc block to 550–600°C, then adding a magnesium block and an aluminum block to obtain the zinc alloy plating solution.

[0048] In some embodiments, the step of preparing the zinc alloy plating solution specifically involves mixing a block of zinc, a block of magnesium, and a block of aluminum, and heating the mixture to 550–600°C to obtain the zinc alloy plating solution.

[0049] In some embodiments, the preheating treatment specifically involves heating the surface of the magnesium alloy substrate to 250–350°C and holding it for 20–30 seconds.

[0050] In this embodiment of the invention, the surface of the magnesium alloy substrate is preheated to ensure that the magnesium alloy substrate has a sufficient thickness to reach the preheating temperature, so as to prevent the temperature of the zinc alloy plating solution from dropping sharply after the magnesium alloy substrate comes into contact with the zinc alloy plating solution, which would reduce the bonding effect of the formed zinc alloy plating layer.

[0051] Magnesium alloy substrates include, but are not limited to, cast and forged magnesium alloys containing Al and not containing Al, such as AZ31, AZ91, AM80, AM60, and WE43.

[0052] In some embodiments, the heating method is selected from one of electric furnace heating, flame heating, laser heating, and electric arc heating.

[0053] In some embodiments, before preheating the magnesium alloy substrate, the process further includes cleaning the magnesium alloy substrate.

[0054] The cleaning process in this embodiment of the invention includes, but is not limited to: using mechanical, chemical, electrochemical, or other methods to grind, polish, and remove oil, impurities, and oxides from the surface of the magnesium alloy substrate.

[0055] This invention provides a zinc alloy coating for inhibiting galvanic corrosion of magnesium alloys, wherein the zinc alloy coating for inhibiting galvanic corrosion of magnesium alloys is prepared by the above-described preparation method.

[0056] In some embodiments, the thickness of the zinc alloy coating is 200-2000 μm.

[0057] In some embodiments, the zinc alloy coating contains 2% to 4% aluminum by mass, 1% to 3% magnesium by mass, and the mass ratio of magnesium to aluminum is 1 / 3 to 2 / 3.

[0058] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, not all embodiments, and are intended only to illustrate the present invention and not to limit it. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0059] Example 1

[0060] The preparation of a zinc alloy coating that inhibits galvanic corrosion of magnesium alloys includes the following steps:

[0061] The surface of the AZ91 magnesium alloy substrate was cleaned to remove impurities and oil, and then ground and polished. Under an argon protective atmosphere, a zinc block was heated to 600℃ to melt, and 2% Mg and 3% Al (by mass) were added. After the Mg and Al were completely melted, the mixture was thoroughly stirred and mixed, then cooled to 350℃ to obtain a molten Zn-3Al-2Mg alloy plating solution. Under an argon protective atmosphere, the surface of the AZ91 magnesium alloy substrate was preheated to 280℃ and held for 20 seconds to ensure a sufficiently thick surface layer reached the desired temperature. Under an argon protective atmosphere, the AZ91 magnesium alloy substrate was immersed in the molten Zn-3Al-2Mg alloy plating solution and held at 350℃ for 30 seconds to allow the AZ91 magnesium alloy substrate and the Zn-3Al-2Mg alloy plating solution to fuse, thermally diffuse, and react, generating an appropriate amount of intermetallic compounds and forming a continuously transitioning diffusion intermediate layer. The zinc alloy-clad magnesium alloy component was cooled at a rate of 10℃ / s. Its SEM image is shown below. Figure 2 As shown, the cross-sectional EDS energy spectrum scan is as follows: Figure 3 As shown.

[0062] Example 2

[0063] The preparation of a zinc alloy coating that inhibits galvanic corrosion of magnesium alloys includes the following steps:

[0064] The surface of the WE43 magnesium alloy substrate was cleaned to remove impurities and oil, and then ground and polished. Under an argon-protected atmosphere, a zinc block was heated to 600°C to melt, and 1% Mg and 3% Al (by mass) were added. After the Mg and Al were completely melted, the mixture was thoroughly stirred and mixed, then cooled to 380°C to obtain a molten Zn-3Al-1Mg alloy plating solution. Under an argon-protected atmosphere, the surface of the WE43 magnesium alloy substrate was preheated to 300°C and held for 20 seconds to ensure a sufficiently thick substrate surface layer reached the desired temperature. Under an argon-protected atmosphere, the WE43 magnesium alloy substrate was immersed in the molten Zn-3Al-1Mg alloy plating solution and held at 380°C for 20 seconds to allow the WE43 magnesium alloy substrate and the Zn-3Al-2Mg alloy plating solution to fuse, thermally diffuse, and react, generating an appropriate amount of intermetallic compounds to form a continuously transitioning diffusion intermediate layer. The zinc alloy-clad magnesium alloy component was cooled at a rate of 5°C / s.

[0065] Performance testing experiment

[0066] The following tests were performed on the zinc alloy-clad magnesium alloy components prepared in Examples 1 and 2:

[0067] (1) Polarization curves of potentiodynamic polarization test (see Table 1 and ) Figure 4The working electrodes were respectively zinc alloy-clad magnesium alloy components, AZ91 magnesium alloy, WE43 magnesium alloy, zinc, and galvanized Q235 steel. The surface area of ​​the working electrode was 1 cm². 2 ; with 1cm 2 A platinum sheet electrode was used as the auxiliary electrode; a saturated calomel electrode was used as the reference electrode. Potentiodynamic polarization tests were performed in a 3.5% w.t NaCl solution at a potential scan rate of 0.167 mV / s.

[0068] Test results show that the corrosion potential of the zinc alloy-clad magnesium alloy component prepared in Example 1 is -1.10V (vs. SCE), and the corrosion current is 2.88 × 10⁻⁶. -6 A / cm 2 Compared to the AZ91 magnesium alloy substrate, the self-corrosion current value decreased significantly, and the corrosion resistance was significantly improved. The zinc alloy-clad magnesium alloy component prepared in Example 2 had a corrosion potential of -1.16V (vs. SCE) and a corrosion current of 4.39 × 10⁻⁶. -6 A / cm 2 Compared to the base WE43 magnesium alloy, the self-corrosion current value is significantly reduced, and the corrosion resistance is significantly improved.

[0069] Table 1

[0070] Ecorr(V vs SCE) <![CDATA[icorr(A / cm 2 ) <!-- 5 -->]]> AZ91 -1.54 <![CDATA[5.19×10 -4 ]]> WE43 -1.72 <![CDATA[2.72×10 -4 ]]> Zn -0.99 <![CDATA[1.76×10 -4 ]]> Example 1 -1.10 <![CDATA[2.88×10 -6 ]]> Example 2 -1.16 <![CDATA[4.39×10 -6 ]]> Galvanized Q235 steel -0.99 <![CDATA[1.17×10 -4 ]]>

[0071] (2) Coupling current (see Figure 5 , Figure 6 , Figure 7 Using the zinc alloy clad magnesium alloy components, AZ91 magnesium alloy, and WE43 magnesium alloy obtained in Examples 1 and 2 as working electrodes, respectively, the test area was 4 cm². 2 Zinc, aluminum, and scratched Q235 galvanized steel (with the base steel exposed at the scratches) were used as the electrode pairs, with a test area of ​​4 cm². 2 The working electrode and the electrode pair were spaced 5 cm apart. The current of each electrode pair was measured in a 3.5% wt. NaCl solution.

[0072] (3) Cross-sectional morphology image of the coating: The zinc alloy clad magnesium alloy component prepared in Example 1 did not show obvious second phase precipitation in the AZ91 magnesium alloy substrate, and exhibited a distinct three-layer structure consisting of a well-bonded magnesium alloy substrate, a diffusion intermediate layer, and a zinc alloy coating (see Figure 8 In Example 2, the zinc alloy clad magnesium alloy component on the WE43 magnesium alloy substrate did not undergo significant phase composition changes. The zinc alloy plating solution reacted fully with the WE43 substrate to form a metallurgical bond, and the cross-section showed a distinct three-layer structure consisting of the magnesium alloy substrate, a diffusion intermediate layer, and a zinc alloy coating (see Example 2). Figure 9 ).

[0073] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a zinc alloy coating that inhibits corrosion and galvanic corrosion of magnesium alloys, characterized in that, The preparation method comprises the following steps: A zinc alloy molten plating solution is prepared, wherein the zinc alloy molten plating solution comprises metallic zinc, metallic aluminum, and metallic magnesium; Preheating treatment is applied to the magnesium alloy substrate; In a protective atmosphere, a preheated magnesium alloy substrate is immersed in the zinc alloy molten plating solution for immersion plating. During the immersion plating process, the temperature of the zinc alloy molten plating solution is 350~380℃. The substrate is removed after immersion for 20~30 seconds and cooled, or left in the plating solution and cooled together with the plating solution. Both of these immersion plating processes can obtain the zinc alloy coating that inhibits magnesium alloy corrosion and galvanic corrosion. Alternatively, in a protective atmosphere, the zinc alloy molten plating solution at a temperature of 350~380℃ is poured onto the surface of a preheated magnesium alloy substrate, held for 20~30s, and then cooled to obtain the zinc alloy coating that inhibits magnesium alloy corrosion and galvanic corrosion. In the zinc alloy molten plating solution, the mass content of aluminum is 2% to 4%, the mass content of magnesium is 1% to 3%, and the mass ratio of magnesium to aluminum is 1 / 3 to 2 / 3. The steps for preparing the zinc alloy molten plating solution are as follows: heating a zinc block to 550~600℃, then adding a magnesium block and an aluminum block to obtain the zinc alloy molten plating solution; Alternatively, the steps for preparing the zinc alloy molten plating solution are as follows: mixing zinc blocks, magnesium blocks, and aluminum blocks, and heating to 550~600℃ to obtain the zinc alloy molten plating solution; The preheating treatment specifically involves heating the surface of the magnesium alloy substrate to 250~350℃ and holding it for 20-30 seconds.

2. The method for preparing a zinc alloy coating that inhibits corrosion and galvanic corrosion of magnesium alloys according to claim 1, characterized in that, The heating method used in the preheating process is selected from one of the following: electric furnace heating, flame heating, laser heating, electric arc heating, and friction heating.

3. The method for preparing a zinc alloy coating that inhibits corrosion and galvanic corrosion of magnesium alloys according to claim 1, characterized in that, Before preheating the magnesium alloy substrate, the process further includes cleaning, leveling, roughening, and / or annealing the magnesium alloy substrate.

4. A zinc alloy coating for inhibiting corrosion and galvanic corrosion of magnesium alloys, characterized in that, The zinc alloy coating that inhibits magnesium alloy corrosion and galvanic corrosion is prepared by the preparation method described in any one of claims 1-3.

5. The zinc alloy coating for inhibiting magnesium alloy corrosion and galvanic corrosion according to claim 4, characterized in that, The thickness of the zinc alloy coating is 200-2000 μm.

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