Preparation method of magnesium alloy surface corrosion-resistant coating in hot rolling compounding process

Abstract

The invention discloses a preparation method of a magnesium alloy surface corrosion-resistant coating in a hot rolling compounding process, and belongs to the technical field of magnesium alloy surface treatment. The invention aims to solve the problems of poor surface corrosion resistance and high protection treatment cost of the existing magnesium alloy plate. The method comprises the following steps: 1, pre-treating a plate; 2, spraying an isolating agent; 3, combined seal welding; 4, vacuumizing; 5, hot rolling; and 6, stripping the plate. On the basis of a hot rolling compounding method, great pressure is applied to alloy contact surfaces through rolling, so that a magnesium alloy plate and an aluminum plate are tightly combined, magnesium-aluminum reaction is activated at high temperature, a reaction layer is formed on an alloy compounding surface, and the reaction layer is broken from one side of the aluminum plate during mechanical stripping, so that a corrosion-resistant coating with a certain thickness is formed on one side of the magnesium alloy plate. According to the method, vacuum protection can be achieved in the rolling process, oxidation of the magnesium alloy plate in the thermal deformation process is avoided, the mechanical property of the rolled magnesium alloy plate is reserved, in addition, the stripped aluminum plate can be repeatedly used, and the cost is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of magnesium alloy surface treatment, and in particular relates to a method for preparing a corrosion-resistant coating on the surface of a magnesium alloy in a hot rolling composite process. Background Art

[0002] Magnesium alloy is one of the lightest metal structural materials known so far, with a density of only 1.7g / cm 3 , which is 2 / 3 of aluminum and 1 / 4 of steel. It has the characteristics of high specific strength and specific stiffness, good machinability, etc. At the same time, magnesium is the eighth most abundant element on earth, and its alloy is considered to be the most promising lightweight material internationally. Since magnesium has the lowest standard electrode potential among metal structural materials, and its oxide film is loose and porous and cannot form a stable and effective protective film, it is prone to corrosion problems such as galvanic corrosion and environmental corrosion in most environments and cannot be used continuously. In order to overcome the limitations of the application of magnesium alloys, the common methods to improve the corrosion resistance of magnesium alloys are surface treatment and surface alloying, among which surface protection technology is the most effective method to protect magnesium alloys.

[0003] At present, there are many methods applied to the surface protection of magnesium alloys, including electrochemical plating, chemical conversion film, anodizing, chemical vapor deposition, micro-arc oxidation, sol-gel method, physical vapor deposition, thermal spraying, etc. However, these methods have their own advantages and disadvantages. For example, the hydrothermal method requires specific experimental conditions, including high temperature and high pressure, which leads to high equipment cost and long reaction time. The chemical vapor deposition method requires expensive equipment and raw materials, complex process, high preparation cost, and is not suitable for large-scale production of magnesium-based materials. Chemical conversion treatment is to generate a stable compound film on the surface of magnesium alloy and treatment liquid through chemical reaction, but the reagents required for this process are toxic and pollute the environment during the treatment process. Anodizing treatment can deposit thin films on a large area and process parts with complex shapes, but the mechanical properties of its thin film are poor. Magnetron sputtering technology, as a deposition method of physical vapor deposition, has the advantages of fast deposition rate and strong bonding with the substrate, but the equipment required is expensive, the overall process is time-consuming, and skilled technicians are required to operate, so the production efficiency is relatively low and the cost is relatively high. Although thermal spraying is widely used, the dust, smoke, light radiation, etc. generated during the coating preparation pose a hidden danger to the health and safety of operators. Therefore, many existing anti-corrosion coating preparation methods are complex and costly, which limits their applicability in certain fields. To address this limitation, it is necessary to develop new coating technologies and more reliable, high-quality coating materials, and comprehensively consider factors such as coating performance, preparation cost, and specific requirements of application scenarios. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of poor surface corrosion resistance and high cost of protective treatment of existing magnesium alloy plates, and to provide a method for preparing a corrosion-resistant coating on the surface of a magnesium alloy in a hot rolling composite process.

[0005] A method for preparing a corrosion-resistant coating on the surface of a magnesium alloy in a hot rolling composite process is specifically completed by the following steps:

[0006] 1. Pretreatment of the board:

[0007] Based on actual processing requirements, magnesium alloy plates and aluminum plates of appropriate sizes are cut, the cut plates are polished flat, and the surfaces to be bonded are cleaned and dried to obtain pretreated magnesium alloy plates and pretreated aluminum plates;

[0008] 2. Paste a peelable adhesive on the middle area of ​​the surfaces to be combined of the pretreated magnesium alloy plate and the pretreated aluminum plate, and then spray a release agent on the edges of the pretreated magnesium alloy plate and the pretreated aluminum plate. After spraying, peel off the peelable adhesive to obtain a magnesium alloy plate and an aluminum plate with a release agent sprayed on the edges of one or both surfaces;

[0009] 3. Two aluminum plates with the edges of one surface sprayed with an isolating agent are respectively arranged on the top and bottom layers of the composite plate, and the surface sprayed with the isolating agent is arranged on the inner side. The top and bottom aluminum plates are then welded and sealed around, and an air pipe with a valve is welded to form a welded package with a sealed cavity.

[0010] The composite plate described in step 3 is a magnesium alloy plate with a release agent sprayed on the edges of both surfaces or a composite plate obtained by alternately stacking a magnesium alloy plate with a release agent sprayed on the edges of both surfaces and an aluminum plate with a release agent sprayed on the edges of both surfaces, and the number of layers of the magnesium alloy plate in the composite plate is one more than the number of layers of the aluminum plate;

[0011] 4. Vacuum the welding package with a sealed cavity to 10 -3 After Pa, close the valve on the air pipe, and finally turn off the vacuum pump to obtain the vacuumized bag;

[0012] 5. Put the vacuumed package into a heating furnace, heat it to the rolling temperature, keep it at the rolling temperature for a period of time and then hot roll it. The composite surfaces of the magnesium alloy plate and the aluminum plate are in close contact and react at high temperature to obtain a hot-rolled plate;

[0013] 6. Cool the hot-rolled plate in a certain way and then cut off the welded edge. Then peel off the top and bottom aluminum plates, and then peel off the magnesium alloy plate. A coating of a certain thickness is formed on the peeled surface of the magnesium alloy plate. The process area of ​​the magnesium alloy plate is cut off. The magnesium alloy plate with the coating on the surface is leveled to obtain a magnesium alloy plate with a corrosion-resistant coating on the surface. This completes the preparation method of the corrosion-resistant coating on the surface of the magnesium alloy in the hot rolling composite process.

[0014] The present invention has the following beneficial effects:

[0015] The present invention proposes a preparation technology of corrosion-resistant coating on the surface of magnesium alloy based on hot rolling composite process, which uses rolling method to make magnesium and aluminum in close contact and react at high temperature to form a compound layer with a certain thickness; because the compound is hard and brittle and the aluminum plate used is relatively soft, when the outer aluminum plate is peeled off by mechanical method, the interface will be torn from the surface of the aluminum plate or broken from the middle of the intermetallic compound layer, thereby forming a corrosion-resistant coating on the surface of the magnesium plate; the present invention also has the following advantages:

[0016] (1) The present invention adopts a vacuum self-sealing structure for rolling, and a common rolling mill can be used to achieve vacuum protection during the rolling process, effectively solving the oxidation problem of magnesium alloy under thermal deformation; at the same time, the aluminum and aluminum alloy plates used in the coating preparation process can be recycled and reused after stripping, greatly reducing the production cost;

[0017] (2) The present invention is based on the hot rolling composite process. When the magnesium-aluminum sheets are composited, the instantaneous contact pressure is extremely large. The formed coating is dense and tightly bonded to the magnesium sheet. While forming the corrosion-resistant coating on the surface of the magnesium alloy, the mechanical properties of the magnesium alloy sheet are guaranteed to a certain extent through work hardening.

[0018] (3) The present invention can symmetrically combine a multi-layer magnesium-aluminum structure to achieve the preparation of surface coatings on multiple magnesium alloy plates during one rolling and compounding process. At the same time, the preparation method based on the rolling process uses simple tools and chemical reagents, which solves the problems of complex technology and high cost of existing magnesium alloy surface treatment methods. It has the advantages of simple process, easy operation, high production efficiency, and environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the stage of the method for preparing the surface coating of the magnesium alloy plate in the hot rolling composite process in Example 1, in which 1 is the top layer of 2219 aluminum alloy plate, 2 is the AZ31 magnesium alloy plate, 3 is the welded edge sealing of the outer layer 2219 aluminum alloy plate, 4 is the core 2219 aluminum alloy plate, 5 is a boron nitride separator, 6 is a rolling roller, and 7 is the magnesium alloy plate with a corrosion-resistant coating on the surface finally obtained;

[0020] Figure 2 Schematic diagram of the spraying of the release agent on the surface of the aluminum plate in Example 1;

[0021] Figure 3 This is a physical picture of the surface of the magnesium alloy plate after rolling and peeling in Example 1;

[0022] Figure 4 This is the XRD pattern of the coating formed on the surface of the magnesium alloy plate in Example 1;

[0023] Figure 5 The polarization curves of the samples after the coating treatment formed on the surface of the magnesium alloy substrate and the magnesium alloy plate in 3.5wt.% NaCl solution;

[0024] Figure 6 It is the surface of the sample after potentiodynamic polarization test;

[0025] Figure 7 The changes in the sample surface at different immersion times in 3.5 wt.% NaCl solution, where (a) is 0 h, (b) is 2 h, (c) is 24 h, and (d) is 48 h. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0028] Specific implementation method 1: This implementation method is a method for preparing a corrosion-resistant coating on the surface of a magnesium alloy in a hot rolling composite process, which is specifically completed in the following steps:

[0029] 1. Pretreatment of the board:

[0030] Based on actual processing requirements, magnesium alloy plates and aluminum plates of appropriate sizes are cut, the cut plates are polished flat, and the surfaces to be bonded are cleaned and dried to obtain pretreated magnesium alloy plates and pretreated aluminum plates;

[0031] 2. Paste a peelable adhesive on the middle area of ​​the surfaces to be combined of the pretreated magnesium alloy plate and the pretreated aluminum plate, and then spray a release agent on the edges of the pretreated magnesium alloy plate and the pretreated aluminum plate. After spraying, peel off the peelable adhesive to obtain a magnesium alloy plate and an aluminum plate with a release agent sprayed on the edges of one or both surfaces;

[0032] 3. Two aluminum plates with the edges of one surface sprayed with an isolating agent are respectively arranged on the top and bottom layers of the composite plate, and the surface sprayed with the isolating agent is arranged on the inner side. The top and bottom aluminum plates are then welded and sealed around, and an air pipe with a valve is welded to form a welded package with a sealed cavity.

[0033] The composite plate described in step 3 is a magnesium alloy plate with a release agent sprayed on the edges of both surfaces or a composite plate obtained by alternately stacking a magnesium alloy plate with a release agent sprayed on the edges of both surfaces and an aluminum plate with a release agent sprayed on the edges of both surfaces, and the number of layers of the magnesium alloy plate in the composite plate is one more than the number of layers of the aluminum plate;

[0034] 4. Vacuum the welding package with a sealed cavity to 10 -3 After Pa, close the valve on the air pipe, and finally turn off the vacuum pump to obtain the vacuumized bag;

[0035] 5. Put the vacuumed package into a heating furnace, heat it to the rolling temperature, keep it at the rolling temperature for a period of time and then hot roll it. The composite surfaces of the magnesium alloy plate and the aluminum plate are in close contact and react at high temperature to obtain a hot-rolled plate;

[0036] 6. Cool the hot-rolled plate in a certain way and then cut off the welded edge. Then peel off the top and bottom aluminum plates, and then peel off the magnesium alloy plate. A coating of a certain thickness is formed on the peeled surface of the magnesium alloy plate. The process area of ​​the magnesium alloy plate is cut off. The magnesium alloy plate with the coating on the surface is leveled to obtain a magnesium alloy plate with a corrosion-resistant coating on the surface. This completes the preparation method of the corrosion-resistant coating on the surface of the magnesium alloy in the hot rolling composite process.

[0037] Specific implementation method 2: The difference between this implementation method and specific implementation method 1 is that: in step 1, the grinding process needs to ensure that the plate is smooth and has no obvious deformation; in step 1, anhydrous ethanol or acetone is used to clean the surface to be bonded until it is clean; the aluminum plate described in step 1 is a pure aluminum plate or an aluminum alloy plate; the aluminum alloy plate is 2219 aluminum alloy. The other steps are the same as those in specific implementation method 1.

[0038] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that: the aluminum plate in step 1 is in the O state; the magnesium alloy plate in step 1 is AZ31 magnesium alloy. The other steps are the same as specific implementation method 1 or 2.

[0039] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the isolation agent in step 2 is boron nitride. The other steps are the same as those in specific embodiments 1 to 3.

[0040] Specific implementation method 5: This implementation method is different from specific implementation methods 1 to 4 in that: the size of the magnesium alloy plate with the release agent sprayed on the edges of the four sides and the aluminum plate with the release agent sprayed on the edges of the four sides described in step 3 are the same, the size of the top and bottom aluminum plates are the same, and the length of the top and bottom aluminum plates is 15mm to 30mm larger than the length of the magnesium alloy plate with the release agent sprayed on the edges of the four sides, and the width of the top and bottom aluminum plates is 15mm to 30mm larger than the width of the magnesium alloy plate with the release agent sprayed on the edges of the four sides. The other steps are the same as specific implementation methods 1 to 4.

[0041] Specific implementation 6: This implementation is different from specific implementations 1 to 5 in that: in step 3, the top and bottom aluminum plates are sealed and welded around to form a cavity, and the cavity size can ensure that the internal composite plate is fixed. The other steps are the same as specific implementations 1 to 5.

[0042] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that the rolling temperature in step 5 is 350°C to 550°C and the holding time in step 5 is 10min to 30min. The other steps are the same as those in specific embodiments 1 to 6.

[0043] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the reduction amount of hot rolling in step 5 is 10% to 50% of the total thickness. The other steps are the same as those of specific embodiments 1 to 7.

[0044] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that the cooling described in step 6 is water cooling. The other steps are the same as those of specific embodiments 1 to 8.

[0045] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that the stripping in step 6 is performed by hand tools or mechanical equipment, and the stripping direction is parallel to or perpendicular to the rolling direction. The other steps are the same as those of specific embodiments 1 to 9.

[0046] The following examples are used to verify the beneficial effects of the present invention:

[0047] Embodiment 1: A method for preparing a corrosion-resistant coating on the surface of a magnesium alloy in a hot rolling composite process, which is specifically completed by the following steps:

[0048] 1. Pretreatment of the board:

[0049] Based on actual processing needs, magnesium alloy plates and aluminum plates were cut by laser, and the surfaces of the cut plates were polished to be smooth using #180 and #400 silicon carbide sandpapers to remove surface pollutants, expose the clean metal matrix, and increase its roughness to facilitate the metallurgical bonding of the subsequent rolling interface. The polished plates were then cleaned with anhydrous ethanol and finally dried with cold air to obtain pretreated magnesium alloy plates and pretreated aluminum plates.

[0050] The aluminum plate described in step 1 is a 2219 aluminum alloy plate with a thickness of 1 mm and an O state;

[0051] The magnesium alloy plate described in step 1 is an AZ31 magnesium alloy plate with a thickness of 1 mm;

[0052] 2. Paste a peelable adhesive on the middle area of ​​the surface to be combined of the pretreated magnesium alloy plate and the pretreated aluminum plate, and then spray an isolating agent (the width of the isolating agent is 20 mm) on the edges of the pretreated magnesium alloy plate or the pretreated aluminum plate. After spraying, peel off the peelable adhesive to obtain a magnesium alloy plate with an isolating agent sprayed on the edges and an aluminum plate with an isolating agent sprayed on the edges;

[0053] The isolation agent described in step 2 is boron nitride;

[0054] 3. Two aluminum plates with the edges of one surface sprayed with an isolating agent are respectively arranged on the top and bottom layers of the composite plate, and the surface sprayed with the isolating agent is arranged on the inner side. The top and bottom aluminum plates are then welded and sealed around, and an air pipe with a valve is welded to form a welded package with a sealed cavity.

[0055] The composite plate described in step 3 is a composite plate obtained by alternately stacking magnesium alloy plates with release agents sprayed on the edges of two surfaces and aluminum plates with release agents sprayed on the edges of two surfaces, and the number of layers of magnesium alloy plates in the composite plate is one more than the number of layers of aluminum plates, that is, magnesium alloy plate-aluminum plate-magnesium alloy plate;

[0056] The magnesium alloy plate with the release agent sprayed on the edges of the four sides described in step 3 is the same size as the aluminum plate with the release agent sprayed on the edges of the four sides, the aluminum plates of the top layer and the bottom layer are the same size, and the length of the aluminum plates of the top layer and the bottom layer is 30 mm larger than the length of the magnesium alloy plate with the release agent sprayed on the edges of the four sides, and the width of the aluminum plates of the top layer and the bottom layer is 30 mm larger than the width of the magnesium alloy plate with the release agent sprayed on the edges of the four sides;

[0057] In step 3, the top and bottom aluminum plates are sealed and welded around to form a cavity, and the cavity size can ensure that the internal composite plate is fixed;

[0058] 4. Vacuum the welding package with a sealed cavity to 10 -3After Pa, close the valve on the air pipe, and finally turn off the vacuum pump to obtain the vacuumized bag;

[0059] 5. Put the vacuumed package into a heating furnace, heat it to the rolling temperature, keep it at the rolling temperature for a period of time and then hot roll it. The composite surfaces of the magnesium alloy plate and the aluminum plate are in close contact and react at high temperature. At this time, a reaction layer of appropriate thickness is formed between the magnesium alloy plate and the aluminum plate, and the reaction layer has high hardness and large brittleness. When the magnesium and aluminum alloy plates are subsequently mechanically peeled off, they will be broken preferentially from the reaction layer. The hot-rolled plate is obtained.

[0060] The rolling temperature described in step 5 is 450°C;

[0061] The insulation time described in step 5 is 20 minutes;

[0062] The hot rolling reduction in step 5 is 40% of the total thickness, and the hot rolling rate is 30 mm / s;

[0063] 6. Cool the hot-rolled plate in a certain way and then cut off the welded edge, then peel off the top and bottom aluminum plates, and then peel off the magnesium alloy plate, a coating of a certain thickness is formed on the peeled surface of the magnesium alloy plate, the process area of ​​the magnesium alloy plate is cut off, and the magnesium alloy plate with the coating on the surface is leveled to obtain a magnesium alloy plate with a corrosion-resistant coating on the surface, that is, the preparation method of the corrosion-resistant coating on the surface of the magnesium alloy in the hot rolling composite process is completed;

[0064] The cooling described in step 6 is water cooling;

[0065] The peeling in step 6 is performed by using a manual tool, and the peeling direction is perpendicular to the rolling direction;

[0066] Figure 3 This is a physical picture of the surface of the magnesium alloy plate after rolling and peeling in Example 1;

[0067] Figure 4 This is the XRD pattern of the coating formed on the surface of the magnesium alloy plate in Example 1;

[0068] Depend on Figure 4 It can be seen that the strong diffraction peaks of the surface phase of the magnesium alloy plate after rolling are all Al2O3, indicating that its main component is dense alumina ceramic. Therefore, during peeling, the composite surface is torn from one side of the aluminum alloy plate, leaving the compound layer on the magnesium alloy plate and a layer of alumina film.

[0069] In order to characterize the corrosion resistance of the coating, the electrochemical performance of the magnesium alloy substrate and the coating was tested at room temperature using a CHI660E electrochemical workstation, with 3.5wt.% NaCl solution as the electrolyte, the working electrode as the sample to be tested, the counter electrode as the platinum electrode, and the reference electrode as the saturated AgCl electrode. In the scanning voltage range of 0.5V relative to the open circuit potential, the polarization curve was scanned from the cathode to the anode at a rate of 1mV / s, as shown in the figure. Figure 5 As shown in Figure 2, the surface of the sample after electrochemical accelerated corrosion is as follows: Figure 6 As shown. The Tafel extrapolation method was used to obtain the self-corrosion data, as shown in Table 1. The results show that compared with the AZ31 magnesium alloy substrate, after the coating was prepared by this method, the self-corrosion current density of the sample decreased by 2 orders of magnitude, the self-corrosion potential increased from about -1.52V to -1.09V, and the corrosion rate of the sample after treatment decreased significantly; at the same time, a passivation zone appeared in the polarization curve of the sample after coating treatment, indicating that the coating has a certain corrosion resistance.

[0070] Table 1

[0071]

[0072] In order to more intuitively compare the corrosion resistance of the samples, the substrate samples and the samples after coating were immersed in 3.5wt.% NaCl solution respectively. Figure 7 As shown in the figure. The magnesium alloy substrate was obviously corroded just 2 hours after immersion, and serious corrosion occurred on the substrate surface after 24 hours ( Figure 7 (c) Left sample); The corrosion phenomenon of the coating prepared by rolling composite is still not obvious after 48h ( Figure 7 (d) Right side specimen).

Claims

1. A method for preparing a corrosion-resistant coating on the surface of a magnesium alloy by a hot rolling composite process, characterized in that The preparation method is specifically completed according to the following steps:

1. Pretreatment of the board: Based on actual processing requirements, magnesium alloy plates and aluminum plates of appropriate sizes are cut, the cut plates are polished flat, and the surfaces to be bonded are cleaned and dried to obtain pretreated magnesium alloy plates and pretreated aluminum plates; 2. Paste a peelable adhesive on the middle area of ​​the surfaces to be combined of the pretreated magnesium alloy plate and the pretreated aluminum plate, and then spray a release agent on the edges of the pretreated magnesium alloy plate and the pretreated aluminum plate. After spraying, peel off the peelable adhesive to obtain a magnesium alloy plate and an aluminum plate with a release agent sprayed on the edges of one or both surfaces; 3. Two aluminum plates with the edges of one surface sprayed with an isolating agent are respectively arranged on the top and bottom layers of the composite plate, and the surface sprayed with the isolating agent is arranged on the inner side. The top and bottom aluminum plates are then welded and sealed around, and an air pipe with a valve is welded to form a welded package with a sealed cavity. The composite plate described in step 3 is a magnesium alloy plate with a release agent sprayed on the edges of both surfaces or a composite plate obtained by alternately stacking a magnesium alloy plate with a release agent sprayed on the edges of both surfaces and an aluminum plate with a release agent sprayed on the edges of both surfaces, and the number of layers of the magnesium alloy plate in the composite plate is one more than the number of layers of the aluminum plate; 4. Vacuum the welding package with a sealed cavity to 10 -3 After Pa, close the valve on the air pipe, and finally turn off the vacuum pump to obtain the vacuumized bag; 5. Put the vacuumed package into a heating furnace, heat it to the rolling temperature, keep it at the rolling temperature for a period of time and then hot roll it. The composite surfaces of the magnesium alloy plate and the aluminum plate are in close contact and react at high temperature to obtain a hot-rolled plate; 6. Cool the hot-rolled plate in a certain way and then cut off the welded edge. Then peel off the top and bottom aluminum plates, and then peel off the magnesium alloy plate. A coating of a certain thickness is formed on the peeled surface of the magnesium alloy plate. The process area of ​​the magnesium alloy plate is cut off. The magnesium alloy plate with the coating on the surface is leveled to obtain a magnesium alloy plate with a corrosion-resistant coating on the surface. This completes the preparation method of the corrosion-resistant coating on the surface of the magnesium alloy in the hot rolling composite process.

2. The method for preparing a corrosion-resistant coating on the surface of a magnesium alloy by hot rolling composite process according to claim 1, characterized in that The grinding process in step one needs to ensure that the plate is smooth and has no obvious deformation; in step one, anhydrous ethanol or acetone is used to clean the surface to be bonded until it is clean; the aluminum plate described in step one is a pure aluminum plate or an aluminum alloy plate; the aluminum alloy plate is 2219 aluminum alloy.

3. The method for preparing a corrosion-resistant coating on the surface of a magnesium alloy by hot rolling composite process according to claim 2, characterized in that The state of the aluminum plate described in step 1 is O state; the magnesium alloy plate described in step 1 is AZ31 magnesium alloy.

4. The method for preparing a corrosion-resistant coating on the surface of a magnesium alloy by hot rolling composite process according to claim 1, characterized in that The isolation agent described in step 2 is boron nitride.

5. The method for preparing a corrosion-resistant coating on the surface of a magnesium alloy by hot rolling composite process according to claim 1, characterized in that The magnesium alloy plate with isolation agent sprayed on all four edges described in step three and the aluminum plate with isolation agent sprayed on all four edges are of the same size, the top and bottom aluminum plates are of the same size, and the length of the top and bottom aluminum plates is 15mm to 30mm larger than the length of the magnesium alloy plate with isolation agent sprayed on all four edges, and the width of the top and bottom aluminum plates is 15mm to 30mm larger than the width of the magnesium alloy plate with isolation agent sprayed on all four edges.

6. The method for preparing a corrosion-resistant coating on the surface of a magnesium alloy by hot rolling composite process according to claim 1, characterized in that In step 3, the top and bottom aluminum plates are sealed and welded around to form a cavity, and the size of the cavity can ensure that the internal composite plate is fixed.

7. The method for preparing a corrosion-resistant coating on the surface of a magnesium alloy by hot rolling composite process according to claim 1, characterized in that The rolling temperature in step 5 is 350° C. to 550° C.; the insulation time in step 5 is 10 min to 30 min.

8. The method for preparing a corrosion-resistant coating on the surface of a magnesium alloy by hot rolling composite process according to claim 1, characterized in that The reduction amount of the hot rolling described in step 5 is 10% to 50% of the total thickness.

9. The method for preparing a corrosion-resistant coating on the surface of a magnesium alloy by hot rolling composite process according to claim 1, characterized in that The cooling described in step six is ​​water cooling.

10. The method for preparing a corrosion-resistant coating on the surface of a magnesium alloy by hot rolling composite process according to claim 1, characterized in that The stripping described in step six is ​​performed by using manual tools or mechanical equipment, and the stripping direction is parallel to the rolling direction or perpendicular to the rolling direction.

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