Magnesium alloy high-binding-force surface treatment liquid and preparation method thereof

Abstract

The invention discloses magnesium alloy high-binding-force surface treatment liquid and a preparation method thereof, and belongs to the technical field of metal material surface modification. The surface treatment liquid comprises the following raw materials in parts by weight: 10-15 parts of carboxymethyl chitosan, 8-12 parts of tannic acid, 5-8 parts of rare earth salt, 5-8 parts of sodium alginate, 8-10 parts of bonding resin, 4-8 parts of nano sol, 12-16 parts of carboxylated carbon nanotubes, 2-4 parts of a dispersing agent and 100 parts of deionized water. Through the strong complexing effect of carboxymethyl chitosan and tannic acid with metal and the synergistic corrosion inhibition effect of rare earth salt and sodium alginate, the situation that the binding force of a subsequent coating is reduced due to corrosion of a base material is avoided, and the high adhesion effect of bonding resin and nano sol is achieved; and carboxylated carbon nanotubes are used for loading corrosion inhibition and adhesion components to improve the roughness of the surface of the treated magnesium alloy, high binding force to a follow-up coating can be achieved under multiple effects, the coating is suitable for magnesium alloys of different marks, and excellent results are shown in scratch, gridding, impact resistance and cup drawing tests.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material surface modification, and in particular relates to a magnesium alloy high-bonding force surface treatment liquid and a preparation method thereof. Background Art

[0002] As an energy-saving and lightweight structural material, magnesium alloy has broad application prospects in lightweight demand fields such as aerospace, energy vehicles, and electronic communications. However, the widespread application of magnesium alloys faces two major bottleneck problems. One is that the active characteristics of magnesium alloys lead to poor corrosion resistance, and the other is that magnesium alloys have poor mechanical properties at room temperature. In terms of mechanical properties, the inherent weak metal bond strength of magnesium alloys is one of the main reasons for the poor mechanical properties, and the weak bonding strength will cause the subsequent functional coating to fall off. Therefore, researchers have mainly done two aspects of work to improve the bonding strength of magnesium alloys: one is to improve it by adding rare earth elements or grain refinement during the manufacturing process of magnesium alloys; the other is to treat the surface of magnesium alloys to improve the bonding strength to subsequent coatings, thereby optimizing the surface treatment performance. Among them, the development of high bonding strength surface treatment liquid is one of the effective means.

[0003] The research focus of using surface treatment liquid to improve the bonding strength of surface treatment is to achieve it through the adhesion of the surface treatment liquid and a certain degree of roughness on the surface of magnesium alloy. As a functional material, carbon nanotubes have the advantages of high tensile strength and elastic modulus, high specific surface area and more defect sites. They can load other adhesive materials to achieve high adhesion and roughness at the same time. Therefore, it is of great significance to develop a high-bonding surface treatment liquid for magnesium alloy based on carbon nanotubes. Summary of the invention

[0004] In order to solve the problem that the magnesium alloy has weak self-bonding strength and easily causes subsequent coating to fall off, the present invention provides a magnesium alloy high-bonding strength surface treatment liquid and a preparation method thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A magnesium alloy high-bonding force surface treatment liquid comprises the following raw materials in parts by weight: 10-15 parts of carboxymethyl chitosan, 8-12 parts of tannic acid, 5-8 parts of rare earth salt, 5-8 parts of sodium alginate, 8-10 parts of adhesive resin, 4-8 parts of nanosol, 12-16 parts of carboxylated carbon nanotubes, 2-4 parts of dispersant and 100 parts of deionized water.

[0007] Furthermore, the rare earth salt is any one of cerium chloride, cerium dioxide, and cerium citrate, or a mixture of any two of them in any mass ratio.

[0008] Furthermore, the adhesive resin is any one of epoxy resin glue and acrylic glue, or a mixture of the two in any mass ratio.

[0009] Furthermore, the nanosol is any one of silicon dioxide nanosol, titanium dioxide nanosol, and aluminum oxide nanosol, or a mixture of any two of them in any mass ratio.

[0010] Furthermore, the particle size of the silicon dioxide nanosol is 10-20 nm, the particle size of the titanium dioxide nanosol is 5-10 nm, and the particle size of the aluminum oxide nanosol is 10-15 nm.

[0011] Furthermore, the carboxylated carbon nanotubes are carboxylated multi-walled carbon nanotubes with a length of 10-20 μm.

[0012] Furthermore, the dispersant is any one of sodium hexametaphosphate, sodium dodecyl sulfate, and sodium dodecylbenzene sulfate, or a mixture of any two of them in any mass ratio.

[0013] Furthermore, the method for preparing the magnesium alloy high-bonding strength surface treatment liquid of the present invention comprises the following steps:

[0014] S1. Weigh each raw material by weight;

[0015] S2. Carboxymethyl chitosan and tannic acid were added to deionized water and stirred at a speed of 500-600 r / min for 1-2 h to form a mixture;

[0016] S3. Add carboxylated carbon nanotubes and dispersant to the mixture obtained in step S2, stir at 700-900 r / min for 20-30 min, and then ultrasonicate for 15-25 min. Then, add rare earth salt, sodium alginate, adhesive resin and nanosol in sequence, and continue stirring for 2-3 hours to obtain a high-bonding surface treatment solution for magnesium alloy.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1. The present invention provides a high-bonding force surface treatment liquid for magnesium alloys, which is mainly composed of carboxymethyl chitosan, tannic acid, rare earth salts, sodium alginate, adhesive resin, nanosol, carboxylated carbon nanotubes, dispersant and deionized water, and the surface treatment liquid can form a film on the surface of the magnesium alloy.

[0019] 2. The present invention utilizes the strong complexation of carboxymethyl chitosan and tannic acid with metals to effectively improve the binding force of the surface treatment liquid on the treated metal surface; the synergistic effect of rare earth salts and sodium alginate can achieve a corrosion inhibition effect on the treated magnesium alloy surface, thereby improving the anti-corrosion performance of subsequent coatings and avoiding the reduction of the binding force of subsequent coatings due to corrosion of the substrate.

[0020] 3. The high adhesion of the adhesive resin and nanosol in the present invention can not only improve the bonding strength with the metal surface, but also help the bonding of subsequent coatings; carboxylated carbon nanotubes have a large specific surface area and many surface defects. After being loaded with corrosion inhibition and adhesion components, they are beneficial to improving the roughness of the treated magnesium alloy surface, thereby further improving the bonding strength of subsequent coatings. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Example 1

[0023] The magnesium alloy high-bonding surface treatment liquid of this embodiment includes the following raw materials in parts by weight: 12 parts of carboxymethyl chitosan, 10 parts of tannic acid, 6 parts of rare earth salt, 6 parts of sodium alginate, 9 parts of adhesive resin, 6 parts of nanosol, 14 parts of carboxylated carbon nanotubes, 3 parts of dispersant, and 100 parts of deionized water. Among them: the rare earth salt is a mixture of cerium chloride and cerium dioxide in a mass ratio of 1:1; the adhesive resin is a mixture of epoxy resin glue and acrylic glue in a mass ratio of 1:1; the nanosol is a mixture of silicon dioxide nanosol with a particle size of 10-20nm and titanium dioxide nanosol with a particle size of 5-10nm in a mass ratio of 1:1; the dispersant is a mixture of sodium hexametaphosphate and sodium dodecyl sulfate in a mass ratio of 1:1.

[0024] The magnesium alloy high-bonding strength surface treatment solution of this embodiment is prepared according to the following steps:

[0025] S1. Weigh each raw material by weight;

[0026] S2. Carboxymethyl chitosan and tannic acid were added to deionized water and stirred at a speed of 550 r / min for 1.5 h to form a mixture;

[0027] S3. Add carboxylated carbon nanotubes and dispersant to the mixture obtained in step S2, stir at 800 r / min for 25 min and then ultrasonicate for 20 min, then add rare earth salt, sodium alginate, adhesive resin and nanosol in sequence, continue stirring for 2.5 h, and obtain a high-bonding surface treatment solution for magnesium alloy.

[0028] Example 2

[0029] The magnesium alloy high-bonding surface treatment liquid of this embodiment includes the following raw materials by weight: 10 parts of carboxymethyl chitosan, 8 parts of tannic acid, 5 parts of rare earth salt, 5 parts of sodium alginate, 8 parts of adhesive resin, 4 parts of nanosol, 12 parts of carboxylated carbon nanotubes, 2 parts of dispersant, and 100 parts of deionized water. Among them: the rare earth salt is a mixture of cerium chloride and cerium citrate mixed in a mass ratio of 1:1; the adhesive resin is epoxy resin glue; the nanosol is a mixture of silicon dioxide nanosol with a particle size of 10-20nm and aluminum oxide nanosol with a particle size of 10-15nm mixed in a mass ratio of 1:1; the dispersant is a mixture of sodium hexametaphosphate and sodium dodecylbenzene sulfate mixed in a mass ratio of 1:1.

[0030] The magnesium alloy high-bonding strength surface treatment solution of this embodiment is prepared according to the following steps:

[0031] S1. Weigh each raw material by weight;

[0032] S2. Carboxymethyl chitosan and tannic acid were added to deionized water and stirred at a speed of 500 r / min for 1 h to form a mixture;

[0033] S3. Add carboxylated carbon nanotubes and dispersant to the mixture obtained in step S2, stir at 700 r / min for 20 min, and then ultrasonicate for 15 min. Then, add rare earth salt, sodium alginate, adhesive resin and nanosol in sequence, and continue stirring for 2 h to obtain a high-bonding surface treatment solution for magnesium alloy.

[0034] Example 3

[0035] The magnesium alloy high-bonding surface treatment liquid of this embodiment includes the following raw materials in parts by weight: 15 parts of carboxymethyl chitosan, 12 parts of tannic acid, 8 parts of rare earth salt, 8 parts of sodium alginate, 10 parts of adhesive resin, 8 parts of nanosol, 16 parts of carboxylated carbon nanotubes, 4 parts of dispersant, and 100 parts of deionized water. Among them: the rare earth salt is a mixture of cerium dioxide and cerium citrate mixed in a mass ratio of 1:1; the adhesive resin is acrylic glue; the nanosol is a mixture of titanium dioxide nanosol with a particle size of 5-10nm and aluminum oxide nanosol with a particle size of 10-15nm mixed in a mass ratio of 1:1; the dispersant is a mixture of sodium hexametaphosphate and sodium dodecylbenzene sulfate mixed in a mass ratio of 1:1.

[0036] The magnesium alloy high-bonding strength surface treatment solution of this embodiment is prepared according to the following steps:

[0037] S1. Weigh each raw material by weight;

[0038] S2. Carboxymethyl chitosan and tannic acid were added to deionized water and stirred at a speed of 600 r / min for 2 h to form a mixture;

[0039] S3. Add carboxylated carbon nanotubes and dispersant to the mixture obtained in step S2, stir at 900 r / min for 30 min and then ultrasonicate for 25 min, then add rare earth salt, sodium alginate, adhesive resin and nanosol in sequence, continue stirring for 3 h, and obtain a high-bonding surface treatment solution for magnesium alloy.

[0040] Example 4

[0041] The magnesium alloy high-bonding surface treatment liquid of this embodiment includes the following raw materials by weight: 13 parts of carboxymethyl chitosan, 11 parts of tannic acid, 7 parts of rare earth salt, 7 parts of sodium alginate, 9 parts of adhesive resin, 7 parts of nanosol, 15 parts of carboxylated carbon nanotubes, 3.5 parts of dispersant, and 100 parts of deionized water. Among them: the rare earth salt is a mixture of cerium chloride and cerium dioxide in a mass ratio of 7:3; the adhesive resin is a mixture of epoxy resin glue and acrylic glue in a mass ratio of 6:4; the nanosol is a mixture of silicon dioxide nanosol with a particle size of 10-20nm and titanium dioxide nanosol with a particle size of 5-10nm in a mass ratio of 3:7; the dispersant is a mixture of sodium hexametaphosphate and sodium dodecyl sulfate in a mass ratio of 4:6.

[0042] The magnesium alloy high-bonding strength surface treatment solution of this embodiment is prepared according to the following steps:

[0043] S1. Weigh each raw material by weight;

[0044] S2. Carboxymethyl chitosan and tannic acid were added to deionized water and stirred at a speed of 580 r / min for 1.5 h to form a mixture;

[0045] S3. Add carboxylated carbon nanotubes and dispersant to the mixture obtained in step S2, stir at 850 r / min for 28 min, and then ultrasonicate for 22 min. Then, add rare earth salt, sodium alginate, adhesive resin and nanosol in sequence, and continue stirring for 2.5 h to obtain a high-bonding surface treatment solution for magnesium alloy.

[0046] Example 5

[0047] The magnesium alloy high-bonding surface treatment liquid of this embodiment includes the following raw materials by weight: 11 parts of carboxymethyl chitosan, 9 parts of tannic acid, 5.5 parts of rare earth salt, 5.5 parts of sodium alginate, 8.5 parts of adhesive resin, 5 parts of nanosol, 13 parts of carboxylated carbon nanotubes, 2.5 parts of dispersant, and 100 parts of deionized water. Among them: the rare earth salt is cerium chloride; the adhesive resin is epoxy resin glue; the nanosol uses a silicon dioxide nanosol with a particle size of 10-20nm; and the dispersant is sodium dodecyl sulfate.

[0048] The magnesium alloy high-bonding strength surface treatment solution of this embodiment is prepared according to the following steps:

[0049] S1. Weigh each raw material by weight;

[0050] S2. Carboxymethyl chitosan and tannic acid were added to deionized water and stirred at a speed of 530 r / min for 1.5 h to form a mixture;

[0051] S3. Add carboxylated carbon nanotubes and dispersant to the mixture obtained in step S2, stir at 750 r / min for 22 min, and then ultrasonicate for 18 min. Then, add rare earth salt, sodium alginate, adhesive resin and nanosol in sequence, and continue stirring for 2.5 h to obtain a high-bonding surface treatment solution for magnesium alloy.

[0052] Comparative Example 1

[0053] The blank control group was used, i.e. no surface treatment solution was used.

[0054] Comparative Example 2

[0055] A magnesium alloy high-bonding strength surface treatment liquid and a preparation method thereof is a control group of Example 1, except that carboxymethyl chitosan is removed from the raw materials and step S2, and the remaining components and preparation steps remain unchanged.

[0056] Comparative Example 3

[0057] A magnesium alloy high-bonding strength surface treatment liquid and a preparation method thereof are the control group of Example 1, except that tannic acid is removed from the raw materials and step S2, and the other components and preparation steps remain unchanged.

[0058] Comparative Example 4

[0059] A magnesium alloy high-bonding strength surface treatment liquid and a preparation method thereof is a control group of Example 1, except that no rare earth salt is added to the raw materials and step S3, and the other components and preparation steps remain unchanged.

[0060] Comparative Example 5

[0061] A magnesium alloy high-bonding strength surface treatment liquid and a preparation method thereof is a control group of Example 1, except that sodium alginate is not added to the raw materials and step S3, and the other components and preparation steps remain unchanged.

[0062] Comparative Example 6

[0063] A magnesium alloy high-bonding strength surface treatment liquid and a preparation method thereof is a control group of Example 1, except that no adhesive resin is added to the raw materials and step S3, and the other components and preparation steps remain unchanged.

[0064] Comparative Example 7

[0065] A magnesium alloy high-bonding strength surface treatment liquid and a preparation method thereof is a control group of Example 1, except that no nanosol is added to the raw materials and step S3, and the other components and preparation steps remain unchanged.

[0066] Comparative Example 8

[0067] A magnesium alloy high-bonding strength surface treatment liquid and a preparation method thereof is a control group of Example 1, except that the raw materials and the carboxylated carbon nanotubes in step S3 are replaced by carbon nanotubes, and the other components and preparation steps remain unchanged.

[0068] Comparative Example 9

[0069] A magnesium alloy high-bonding strength surface treatment liquid and a preparation method thereof, which is the control group of Example 1, except that no carboxylated carbon nanotubes are added to the raw materials and step S3, S1 and S2 remain unchanged, and S3 is replaced by: adding a dispersant, a rare earth salt, sodium alginate, a bonding resin and a nanosol to the above mixture in sequence, and continuing to stir for 2.5 hours to obtain a magnesium alloy high-bonding strength surface treatment liquid.

[0070] For the magnesium alloy high-bonding force surface treatment liquid prepared by Example 1 to Example 5 and Comparative Example 1 to Comparative Example 9, four different grades of magnesium alloys, AZ91D, AZ31B, ZK61M and LA43M, were first surface treated; after the treatment, waterborne polyurethane was continuously coated on the surface to form an organic coating after curing; finally, the coating was subjected to a performance test; the surface treatment process, waterborne polyurethane coating experimental steps and performance test method are as follows:

[0071] 1. Surface treatment process of magnesium alloy with high bonding strength surface treatment liquid:

[0072] The magnesium alloy was polished to a bright finish and cleaned with acetone until the surface was clean; the pretreated magnesium alloy sample was immersed in a magnesium alloy high-bonding strength surface treatment liquid, stirred at 500 r / min for 60 min, taken out and cured and dried in a 50°C drying oven for 2 h to obtain a magnesium alloy sample treated with a high-bonding strength surface treatment liquid.

[0073] 2. Waterborne polyurethane coating experimental steps:

[0074] Aqueous polyurethane (solid content 60%) was evenly coated on the surface of the magnesium alloy sample treated with a high-bonding strength surface treatment liquid, with a coating thickness of about 1 mm; the coated sample was cured and dried in a 90°C drying oven for 3 hours, thereby forming a polyurethane organic coating on the surface.

[0075] 3. Performance test method:

[0076] Corrosion resistance: The samples are subjected to a neutral salt spray test (GB / T 10125-2021). After 720 hours of testing, if there is no rust on the coating surface, it is qualified, otherwise it is unqualified.

[0077] Scratch test: Use a hard steel scratcher with a cutting edge ground to a 30° acute angle to scratch two parallel lines 2 mm apart on the surface of the test sample. Apply enough pressure when scratching so that the scratcher can cut through the film layer and reach the substrate in one go. Stick tape on the scratched area, lift the tape and observe whether there is a film layer on the surface of the tape. If there is a film layer, it is considered unqualified, otherwise it is considered qualified.

[0078] Cross-cut test: The samples are subjected to a cross-cut test (GB / T 9286-2021) and graded according to the degree of coating shedding in the cutting area.

[0079] Impact resistance test: refer to GB / T 1732-2020 "Determination of impact resistance of paint film", the weight of the impact tester is 1kg, the test height is 30cm, and the coating of the sample is observed for cracks and peeling. If there is no crack or peeling, it is considered qualified, otherwise it is considered unqualified.

[0080] Cupping test: Refer to GB / T 4156-2020 "Erichsen cupping test for metal sheets and strips". The test is carried out using a cupping tester. The specified punching depth is 3.5mm. When the specified depth is reached, the sample is taken out and the coating is observed for cracks or peeling. If there is no crack or peeling, it is considered qualified, otherwise it is considered unqualified.

[0081] The above performance test results are shown in Tables 1 and 2:

[0082] Table 1

[0083]

[0084] Table 2

[0085]

[0086] From Tables 1 and 2, we can see that:

[0087] Examples 1, 2, 3, 4, and 5 are the performance test results of the organic coating formed after the surface treatment of magnesium alloy and water-based polyurethane coating using the magnesium alloy high-bonding strength surface treatment liquid prepared under different parameter settings. The results show that the magnesium alloy high-bonding strength surface treatment liquid prepared by the present invention is suitable for magnesium alloys of different grades, is conducive to achieving high bonding strength of subsequent coatings, and the scratch, crosshatch, impact resistance and cupping tests all show excellent results.

[0088] From the comparison between Comparative Example 1 and Example 1, it can be seen that the high bonding strength surface treatment liquid can greatly improve the bonding strength between the treated magnesium alloy and the subsequent coating, and the bonding strength performance test results of the subsequent coating of the magnesium alloy not treated with the surface treatment liquid all failed.

[0089] By comparing Comparative Examples 2 and 3 with Example 1, it can be seen that the carboxymethyl chitosan and tannic acid in the high-binding strength surface treatment liquid can improve the bonding strength between the magnesium alloy after surface treatment liquid treatment and the subsequent coating. This is because carboxymethyl chitosan and tannic acid can form a strong complexation with the metal.

[0090] By comparing Comparative Examples 4 and 5 with Example 1, it can be seen that the rare earth salts and sodium alginate in the high-bonding strength surface treatment solution can not only improve the corrosion resistance of the treated coating, but also improve the bonding strength between the magnesium alloy and the subsequent coating. This is attributed to the synergistic corrosion inhibition effect of the corrosion inhibition components of the rare earth salts and sodium alginate, and the improvement in corrosion resistance can effectively avoid the corrosion of the substrate and cause a decrease in the bonding strength of the subsequent coating.

[0091] By comparing Comparative Examples 6 and 7 with Example 1, it can be seen that the adhesive resin and nanosol in the high-bonding strength surface treatment liquid can improve the bonding strength between the treated magnesium alloy and the subsequent coating, and the high adhesion effect of the adhesive resin and nanosol can significantly improve the bonding strength of the coating.

[0092] By comparing Comparative Example 8 with Example 1, it can be seen that when carbon nanotubes are used instead of carboxylated carbon nanotubes to load corrosion inhibition and adhesion components, the subsequent coating adhesion of the magnesium alloy treated with the surface treatment solution decreases. This is because the carboxylated carbon nanotubes are more conducive to dispersion in the solution, so that the distribution of the loaded components is more uniform, which is conducive to improving the uniformity of the surface after treatment, thereby further improving the adhesion of the subsequent coating. By comparing Comparative Example 9 with Example 1, it can be seen that carboxylated carbon nanotubes can greatly improve the adhesion of the subsequent coating of the magnesium alloy after the surface treatment solution is treated. This is because the carboxylated carbon nanotubes have a large specific surface area and many surface defects. After loading corrosion inhibition and adhesion components, it is conducive to improving the roughness of the surface of the magnesium alloy after treatment, thereby better improving the adhesion of the subsequent coating.

[0093] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0094] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A magnesium alloy high bonding strength surface treatment liquid, It is characterized in that The invention comprises the following raw materials in parts by weight: 10-15 parts of carboxymethyl chitosan, 8-12 parts of tannic acid, 5-8 parts of rare earth salt, 5-8 parts of sodium alginate, 8-10 parts of adhesive resin, 4-8 parts of nanosol, 12-16 parts of carboxylated carbon nanotubes, 2-4 parts of dispersant, and 100 parts of deionized water.

2. The magnesium alloy high bonding strength surface treatment liquid according to claim 1, It is characterized in that The rare earth salt is any one of cerium chloride, cerium dioxide, and cerium citrate, or any two of them mixed in any mass ratio.

3. The magnesium alloy high bonding strength surface treatment liquid according to claim 1, It is characterized in that The adhesive resin is any one of epoxy resin glue and acrylic glue, or a mixture of the two in any mass ratio.

4. The magnesium alloy high bonding strength surface treatment liquid according to claim 1, It is characterized in that The nano-sol is any one of silicon dioxide nano-sol, titanium dioxide nano-sol and aluminum oxide nano-sol or a mixture of any two of them in any mass ratio.

5. The magnesium alloy high bonding strength surface treatment liquid according to claim 4, It is characterized in that The particle size of the silicon dioxide nanosol is 10-20 nm, the particle size of the titanium dioxide nanosol is 5-10 nm, and the particle size of the aluminum oxide nanosol is 10-15 nm.

6. The magnesium alloy high bonding strength surface treatment liquid according to claim 1, It is characterized in that The carboxylated carbon nanotubes are carboxylated multi-walled carbon nanotubes with a length of 10-20 μm.

7. The magnesium alloy high bonding strength surface treatment liquid according to claim 1, It is characterized in that The dispersant is any one of sodium hexametaphosphate, sodium dodecyl sulfate, and sodium dodecylbenzene sulfate, or any two of them mixed in any mass ratio.

8. A method for preparing the magnesium alloy high-bonding strength surface treatment solution according to any one of claims 1 to 7, It is characterized in that The steps include: S1. Weigh each raw material by weight; S2. Carboxymethyl chitosan and tannic acid were added to deionized water and stirred at a speed of 500-600 r / min for 1-2 h to form a mixture; S3. Add carboxylated carbon nanotubes and dispersant to the mixture obtained in step S2, stir at 700-900 r / min for 20-30 min, and then ultrasonicate for 15-25 min. Then, add rare earth salt, sodium alginate, adhesive resin and nanosol in sequence, and continue stirring for 2-3 hours to obtain a high-bonding surface treatment solution for magnesium alloy.

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