Preparation method and application of intelligent anti-corrosion coating based on carboxylated carbon nanotubes grafted with ionic liquid

Abstract

The present invention provides a method for preparing an intelligent anti-corrosion coating based on carboxylated carbon nanotubes grafted with ionic liquids. First, a magnesium alloy with a surface-grown MAO coating is obtained; then the MAO coating is sequentially sealed with phenolphthalein PP and CCNT-[MimAE][APA] to obtain the coating. The intelligent anti-corrosion coating prepared by the method of the present invention not only greatly improves the corrosion resistance of the magnesium alloy, but also simultaneously gives the coating self-repair and self-reporting functions. Once the coating is corroded, phenolphthalein will undergo a color reaction, which can provide a timely warning of early corrosion and play a self-reporting role. At the same time, CCNT-[MimAE][APA] can also repair the damaged parts in time to achieve a self-repair function. The preparation method provided by the present invention is simple, and the prepared intelligent anti-corrosion coating not only has a sensitive self-reporting response, but also has excellent anti-corrosion performance and self-repairing performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical materials and metal anti-corrosion, and particularly relates to a preparation method and application of an intelligent anti-corrosion coating based on carboxylated carbon nanotubes grafted with ionic liquids. Background Art

[0002] Magnesium alloys have the advantages of low density, high specific strength, and excellent casting properties, and have attracted widespread attention in the fields of aerospace, automobiles, communications, and portable microelectronics. However, the poor corrosion resistance of magnesium alloys remains a challenge, which greatly hinders the large-scale application of magnesium alloys. It is well known that alloys exposed to corrosive environments will cause electrochemically driven corrosion. Therefore, it is very necessary to detect and repair early corrosion in a timely manner. Protective coatings are considered to be an effective method to prevent corrosion of magnesium alloys with high chemical reactivity. Among the many protective coatings, micro-arc oxidation (MAO) coatings have better adhesion, wear resistance and corrosion resistance than traditional chemical conversion coatings, and are one of the most effective ways to improve the performance of magnesium alloys. Unfortunately, the micropores and microcracks in the MAO coating provide feasible channels for the penetration of corrosive substances, thereby reducing the actual strengthening effect on magnesium alloys.

[0003] Ionic liquids (ILs), also known as ionic liquids, are a class of compounds composed of organic cations and inorganic (or organic) anions that are liquid at or near room temperature. Generally, ILs have the characteristics of low melting point, high polarity, low toxicity, good chemical stability, and minimal environmental and biological hazards. They have become green and environmentally friendly corrosion inhibitors and are widely used in metal corrosion protection.

[0004] Carbon nanotubes (CNTs) are carbon atoms connected by sp 2 The hexagonal ring network topology formed by hybridization offers advantages such as low density, large specific surface area, excellent mechanical and electromagnetic properties, and has become one of the most promising low-dimensional nanomaterials. Given the interwoven network structure of CNTs within coatings, composite materials can reduce gaps in the coating, increase its compactness, and prevent the penetration of corrosive media. Furthermore, the high electrical potential of the CNT composite material promotes metal passivation, forming a protective layer. Therefore, CNTs can be used in coatings of light alloys to enhance the coating's corrosion resistance.

[0005] Currently, the protective coatings developed generally only have anti-corrosion functions, and only a very small number of coatings have other functions such as self-healing and self-reporting. In general, intelligent anti-corrosion coatings with excellent performance and diverse functions are still extremely scarce. Therefore, adding special materials (such as ionic liquid-grafted carboxylated carbon nanotubes) to micro-arc oxidation coatings to improve the overall performance of magnesium alloys and give them other new functions is bound to be one of the important directions for the development of intelligent anti-corrosion coatings in the future. Summary of the Invention

[0006] Based on this, it is necessary to address the technical problem of how to improve the corrosion protection function of magnesium alloys. The present invention provides a preparation method and application of an intelligent anti-corrosion coating based on carboxylated carbon nanotubes grafted with ionic liquids.

[0007] The primary purpose of the present invention is to provide an intelligent anti-corrosion coating based on carboxylated carbon nanotubes grafted with ionic liquids, which is also called MAO / PP / CCNT-[MimAE][APA] intelligent anti-corrosion coating.

[0008] Another object of the present invention is to provide a method for preparing an intelligent anti-corrosion coating based on carboxylated carbon nanotubes grafted with ionic liquids. The method for preparing the intelligent anti-corrosion coating is also called the method for preparing the MAO / PP / CCNT-[MimAE][APA] intelligent anti-corrosion coating. The intelligent anti-corrosion coating prepared by this method can not only greatly improve the corrosion resistance of magnesium alloys, but also has new functions such as self-repair and self-reporting.

[0009] Another object of the present invention is to provide an application of an intelligent anti-corrosion coating based on carboxylated carbon nanotubes grafted with ionic liquids, which is also called the application of MAO / PP / CCNT-[MimAE][APA] intelligent anti-corrosion coating.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

[0011] A method for preparing an intelligent anti-corrosion coating based on carboxylated carbon nanotubes grafted with ionic liquids comprises the following steps:

[0012] 1) Preparation of MAO coating on the surface of magnesium alloy;

[0013] 2) Preparation of MAO / CCNT-[MimAE][APA] composite coating or MAO / PP / CCNT-[MimAE][APA] composite coating:

[0014] The magnesium alloy with the MAO coating on its surface was placed in a suction filtration bottle and vacuum treated for 15-40 minutes using a circulating water vacuum pump. Then, a 90-110 mg / L anhydrous ethanol solution containing CCNT-[MimAE][APA] corrosion inhibitor was added. The vacuum treatment was continued for 45-90 minutes, and then heated at 30-50°C for 3-5 hours. The alloy was taken out and dried to obtain a MAO / CCNT-[MimAE][APA] composite coating.

[0015] Specifically, the CCNT-[MimAE][APA] corrosion inhibitor is prepared by grafting carboxylated carbon nanotubes (CCNTs) and ionic liquids ([MimAE]Cl) via a simple amide reaction to generate CCNT-[MimAE]Cl. Furthermore, CCNT-[MimAE][APA] is obtained by an ion exchange reaction between β-alanine and CCNT-[MimAE]Cl. The specific preparation steps are as follows:

[0016] a) reacting carboxylated carbon nanotubes (CCNT) with [MimAE]Cl in methanol at 50-70° C. for 8-15 h, and then at 100-120° C. for 20-30 h to obtain CCNT-[MimAE]Cl;

[0017] b) In the presence of aqueous solvent, CCNT-[MimAE]Cl is reacted with β-alanine at 60-70° C. for 20-30 h, and then filtered, washed, and dried to obtain CCNT-[MimAE][APA].

[0018] Furthermore, in step a), the mass ratio of carboxylated carbon nanotubes CCNT and [MimAE]Cl is (0.7-0.9): (2.2-2.3).

[0019] Furthermore, in step a), the molar ratio of β-alanine to CCNT-[MimAE]Cl is (0.9-1.1):(0.9-1.1).

[0020] In the above method, the preparation of MAO / PP / CCNT-[MimAE][APA] composite coating is specifically as follows:

[0021] The magnesium alloy with the MAO coating on its surface is placed in a suction filtration bottle and vacuum-treated using a circulating water vacuum pump for 15-40 minutes. An anhydrous ethanol solution containing phenolphthalein PP is then added, and the vacuum treatment is continued for 45-90 minutes. The mixture is then heated at 30-50° C. for 3-5 hours and then air-dried at room temperature to obtain a MAO / PP composite coating.

[0022] The prepared MAO / PP composite coating was placed in a suction filtration bottle, and a 90-110 mg / L anhydrous ethanol solution containing CCNT-[MimAE][APA] corrosion inhibitor was added. After continuing the vacuum treatment for 45-90 minutes, the coating was heated at 30-50°C for 3-5 hours, taken out, and dried to obtain the MAO / PP / CCNT-[MimAE][APA] composite coating.

[0023] Furthermore, the concentration of the anhydrous ethanol solution containing phenolphthalein PP is 20 to 40 g / L, preferably 25 to 35 g / L.

[0024] In the above method, the MAO coating is prepared on the surface of the magnesium alloy by using a polished, cleaned and dried magnesium alloy sample as an anode and a stainless steel electrode as a cathode, and then placing it in an electrolyte for MAO treatment to obtain a magnesium alloy with a MAO coating grown on the surface.

[0025] Furthermore, the electrolyte composition is: 10-30 g / L sodium silicate, 5-20 g / L potassium hydroxide and 5-15 g / L potassium fluoride; the pulse current density of MAO treatment is 30-60 mA / cm 2 .

[0026] The present invention provides an intelligent anti-corrosion coating based on ionic liquid grafted carboxylated carbon nanotubes prepared by the above-mentioned preparation method.

[0027] The present invention also provides the use of the above-mentioned intelligent anti-corrosion coating based on ionic liquid grafted carboxylated carbon nanotubes in metal corrosion self-reporting and corrosion prevention. Furthermore, the metal is preferably a magnesium alloy.

[0028] In the intelligent anti-corrosion coating based on ionic liquid grafted carboxylated carbon nanotubes described in the present invention, the molecular structural formula of the ionic liquid grafted carboxylated carbon nanotubes is shown below for reference; the intelligent anti-corrosion coating includes MAO, PP and CCNT-[MimAE][APA], and is prepared by first preparing an MAO coating on the surface of a magnesium alloy, and then sealing the MAO coating with PP and CCNT-[MimAE][APA] in sequence.

[0029]

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1) In the present invention, the sealing treatment method for the micro-arc oxidation coating (MAO coating) prepared by the ionic liquid-grafted carboxylated carbon nanotubes and the color developer phenolphthalein (PP) is simple and easy to operate. The surface of the prepared coating is uniform and flat, and it has good bonding ability with the micro-arc oxidation coating. It has good self-repair and self-reporting properties and has a low corrosion current density, which can greatly improve the long-term corrosion resistance of magnesium alloys.

[0032] 2) The intelligent anti-corrosion coating prepared by the method of the present invention not only greatly improves the corrosion resistance of magnesium alloys, but also gives the coating self-repair and self-reporting functions. Once the coating is corroded, phenolphthalein will undergo a color reaction, which can provide timely warning of early corrosion and play a self-reporting role. At the same time, CCNT-[MimAE][APA] can also repair damaged parts in time to achieve self-repair function. The preparation method provided by the present invention is simple, and the prepared intelligent anti-corrosion coating not only has a sensitive self-reporting response, but also has excellent anti-corrosion performance and self-repair performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 SEM images of different coatings prepared on the surface of AZ31B magnesium alloy: (a) MAO coating; (b) MAO / CCNT composite coating; (c) MAO / CCNT-[MimAE][APA] composite coating;

[0034] Figure 2 Middle, left is a cross-sectional view of the MAO / CCNT-[MimAE][APA] composite coating prepared on the surface of AZ31B magnesium alloy; right are EDS mapping images of Mg, F, Si, O, N and C elements respectively;

[0035] Figure 3 The potentiodynamic polarization curves of different coatings prepared on the surface of AZ31B magnesium alloy;

[0036] Figure 4 The scratch test diagram of different coatings prepared on the surface of AZ31B magnesium alloy;

[0037] Figure 5 Self-reported performance test chart of different coatings prepared on the surface of AZ31B magnesium alloy. DETAILED DESCRIPTION

[0038] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar modifications without violating the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0039] Unless otherwise specified, all raw materials used in the following examples are commercially available or prepared according to conventional methods in the art. For example, carboxylated carbon nanotubes (CCNTs) with a carboxyl content of approximately 2.00 wt.% (purity >95%; length: 0.5-2 μm; diameter: 10-20 nm; inner diameter: 5-10 nm) were purchased from Nanjing XFNANO Materials Technology Co., Ltd. Room temperature refers to 25±5°C.

[0040] Example 1

[0041] 1. Pretreatment of magnesium alloy:

[0042] (1) AZ31B magnesium alloy was machined into samples with a size of 1.5 cm × 1.5 cm × 0.6 cm, and the substrate was coated with epoxy resin, leaving only a 1.5 cm × 1.5 cm working surface;

[0043] (2) The AZ31B magnesium alloy sample was then polished with 180, 600, 1500, and 3000 grit sandpaper in sequence, and then polished with W3.5 diamond polishing paste (Veiyee, model PG);

[0044] (3) Finally, use distilled water and anhydrous ethanol to ultrasonically clean for 10 minutes each, dry at 60℃ for 24 hours, and set aside.

[0045] 2. Preparation of MAO Coating

[0046] (1) The stainless steel electrode was used as the cathode, and the pretreated magnesium alloy sample was used as the anode, and placed in MAO electrolyte for micro-arc oxidation treatment for 15 min;

[0047] The MAO treatment parameters were: voltage 300 V, current 30 mA / cm 2 The duty cycle is 20%, the frequency is 500 Hz, and the temperature of the MAO electrolyte is about 40°C during the whole process. The electrolyte is stirred with a magnet to avoid excessive temperature in some parts of the electrolyte.

[0048] MAO electrolyte mainly adopts silicate electrolyte. The preparation process is as follows: weigh 15g sodium silicate, 10g potassium hydroxide and 5g potassium fluoride in a beaker, add 1L distilled water, stir and dissolve to prepare MAO electrolyte;

[0049] (2) The treated MAO sample was ultrasonically cleaned with distilled water for 10 min and dried at room temperature to obtain a MAO coating on the magnesium alloy surface (see Figure 1 (a)

[0050] 3. Preparation of MAO / CCNT Composite Coating

[0051] (1) Place the prepared MAO coating sample in a suction filtration bottle and vacuum treat it using a circulating water vacuum pump for 20 minutes;

[0052] (2) Then, 100 mg / L of anhydrous ethanol solution containing CCNT was added to the filtration flask, and the vacuum treatment was continued (the vacuum degree was maintained at 0.08 MPa) for 1 hour, and then heated at 40 ° C for 4 hours to obtain the MAO / CCNT composite coating (see Figure 1 (b)

[0053] Example 2

[0054] 1. Preparation of CCNT-[MimAE][APA]

[0055] (1) In acetonitrile solvent, 1-methylimidazole and 2-chloroethylamine hydrochloride were reacted at 70°C under argon atmosphere for 24 h to prepare [MimAE]Cl. For details, please refer to the existing literature (F. Lu, X. Gao, X. Yan, H. Gao, L. Shi, H. Jia, L. Zheng, Preparation and characterization of nonaqueous proton-conducting membranes with protic ionic liquids, ACS Appl. Mater. Interfaces 5 (2013) 7626-7632.) for preparation;

[0056] (2) In approximately 40 ml of methanol solvent, 0.8 g of CCNT was reacted with 2.24 g of [MimAE]Cl at 60°C for 12 h, and then at 110°C for another 24 h. After the reaction was completed, the mixture was centrifuged, washed, and dried at 60°C for 24 h to obtain CCNT-[MimAE]Cl.

[0057] (3) In the presence of approximately 40 ml of aqueous solvent, 3.6 mmol of CCNT-[MimAE]Cl was reacted with 0.03 g (3.4 mmol) of β-alanine at 65°C for 24 h. The mixture was filtered, washed with ethanol, and dried at 60°C for 24 h to obtain CCNT-[MimAE][APA].

[0058] 2. Preparation of MAO / CCNT-[MimAE][APA] Composite Coating

[0059] (1) Place the prepared MAO coating sample in a suction filtration bottle and vacuum treat it using a circulating water vacuum pump for 20 minutes;

[0060] (2) Then, 100 mg / L of anhydrous ethanol solution containing CCNT-[MimAE][APA] corrosion inhibitor was added to the filtration bottle, and the vacuum treatment was continued (the vacuum degree was maintained at 0.08 MPa) for 1 hour, and then heated at 40 ° C for 4 hours, taken out, and dried at room temperature for 12 hours to obtain MAO / CCNT-[MimAE][APA] composite coating (see Figure 1 (c)

[0061] Example 3

[0062] Preparation of MAO / PP / CCNT-[MimAE][APA] intelligent anti-corrosion coating

[0063] (1) Place the prepared MAO coating sample in a suction filtration bottle and vacuum treat it using a circulating water vacuum pump for 20 minutes;

[0064] (2) Then, a 30 g / L anhydrous ethanol solution containing phenolphthalein PP was added to the filtration flask, and the vacuum treatment was continued (the vacuum degree was maintained at 0.08 MPa) for 1 hour, and then heated at 40°C for 4 hours, and then air-dried at room temperature to obtain the MAO / PP composite coating;

[0065] (3) The MAO / PP composite coating sample obtained in step (2) was placed in a suction filtration bottle, and then a 100 mg / L anhydrous ethanol solution containing CCNT-[MimAE][APA] corrosion inhibitor was added to the suction filtration bottle. After continuing the vacuum treatment (the vacuum degree was maintained at 0.08 MPa) for 1 hour, it was heated at 40°C for 4 hours, taken out, and dried at room temperature for 12 hours to obtain the MAO / PP / CCNT-[MimAE][APA] intelligent anti-corrosion coating.

[0066] Figure 1 The SEM images of different coatings prepared on the magnesium alloy surface in Example 1 are given: (a) MAO coating; (b) MAO / CCNT composite coating; (c) MAO / CCNT-[MimAE][APA] composite coating. Figure 1 As shown, SEM characterization shows that the surface of the MAO coating prepared in Example 1 of the present invention is uniform and flat, with certain micropores and microcracks ( Figure 1 (a). The SEM characterization results of the MAO / CCNT composite coating after sealing treatment with carboxylated carbon nanotubes (CCNT) show that the coating surface becomes more dense ( Figure 1 b), indicating that CCNT has successfully entered the pores of the MAO coating. The SEM characterization results of the MAO / CCNT-[MimAE][APA] composite coating after CCNT-[MimAE][APA] sealing treatment show that its micropores and microcracks have disappeared, and the coating surface has become more dense ( Figure 1(c) This indicates that CCNT-[MimAE][APA] has also successfully entered the pores of the MAO coating.

[0067] In order to further prove that CCNT-[MimAE][APA] is targetedly inserted into the micropores of MAO, the present invention also made a cross-sectional view of the MAO / CCNT-[MimAE][APA] composite coating (see Figure 2 ). Figure 2 In the figure, the left side shows the cross-sectional view of the MAO / CCNT-[MimAE][APA] composite coating. In order to confirm the insertion of CCNT-[MimAE][APA] in the coating, EDS mapping was also performed along the cross-sectional image of the MAO / CCNT-[MimAE][APA] sample, as shown in Figure 2. Figure 2 As shown on the right, Mg, F, Si, O, N, and C are nearly uniformly distributed across the cross-section of the MAO / CCNT-[MimAE][APA] coating, indicating that [MimAE][APA] anchored to the CCNTs is incorporated into the pores rather than the surface. These data demonstrate that CCNT-[MimAE][APA] is selectively inserted into the micropores of MAO.

[0068] The corrosion resistance of the samples prepared in Examples 1 and 2 was tested in a 3.5 wt.% NaCl solution using an electrochemical method. Their potentiodynamic polarization curves are shown in FIG. Figure 3 As shown. Figure 3 It can be seen that the corrosion current density of the MAO / CCNT-[MimAE][APA] composite coating prepared in Example 2 is 9.11×10 –9 A / cm 2 Compared with the corrosion current density of AZ31B magnesium alloy (1.864×10 –4 A / cm 2 ) is reduced by 5 orders of magnitude, compared with the corrosion current density of MAO coating (1.428×10 – 7 A / cm 2 ) is reduced by 2 orders of magnitude, compared with the corrosion current density of MAO / CCNT composite coating (1.863×10 –8 A / cm 2 ) decreased by one order of magnitude, indicating that the MAO / CCNT-[MimAE][APA] composite coating greatly improved the corrosion resistance of the magnesium alloy.

[0069] Figure 4 The scratch test diagrams of different coatings prepared on the magnesium alloy surface in Examples 1 and 2 are given. Figure 4It can be seen intuitively that the MAO / CCNT-[MimAE][APA] composite coating of the present invention has good self-healing performance. After immersion in 3.5wt.% NaCl solution for 14 days (336h), the corrosion phenomenon at the scratches is relatively small. However, in other coatings without corrosion inhibitors, such as MAO coatings and MAO / CCNT composite coatings, obvious corrosion phenomena occurred after immersion for the same time.

[0070] The two prepared composite coatings were subjected to a salt spray test in a 5 wt.% sodium chloride solution, and the color changes were observed at different times. Figure 5 Self-reported experiments on two composite coatings, MAO / PP / CCNT and MAO / PP / CCNT-[MimAE][APA], are given. Figure 5 The results showed that both MAO / PP / CCNT and MAO / PP / CCNT-[MimAE][APA] coatings showed obvious pink color after 12 minutes, indicating that they had good self-reporting function.

[0071] In summary, the intelligent anti-corrosion coating based on carboxylated carbon nanotubes grafted with ionic liquids described in the present invention has a simple preparation method, and the surface of the obtained intelligent anti-corrosion coating is uniform and dense. It can not only greatly improve the corrosion resistance of magnesium alloys, but also has new functions such as self-repair and self-reporting, and can provide long-term corrosion protection for magnesium alloys.

[0072] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make several improvements without departing from the spirit of the present invention, and these improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing an intelligent anti-corrosion coating based on carboxylated carbon nanotubes grafted with ionic liquids, characterized in that: The steps include: 1) Preparation of MAO coating by micro-arc oxidation on magnesium alloy surface; 2) Preparation of MAO / CCNT-[MimAE][APA] composite coating or MAO / PP / CCNT-[MimAE][APA] composite coating: The magnesium alloy with the MAO coating on its surface was placed in a suction filtration bottle and vacuum-treated using a circulating water vacuum pump for 15-40 minutes. Then, a 90-110 mg / L anhydrous ethanol solution containing CCNT-[MimAE][APA] corrosion inhibitor was added. The vacuum treatment was continued for 45-90 minutes, and then the alloy was heated at 30-50°C for 3-5 hours, removed, and dried to obtain a MAO / CCNT-[MimAE][APA] composite coating. The CCNT-[MimAE][APA] corrosion inhibitor is prepared by the following steps: a) reacting carboxylated carbon nanotubes (CCNTs) with 1-(2-aminoethyl)-3-methylimidazolium chloride ([MimAE]Cl) in methanol at 50-70 °C for 8-15 h, and then at 100-120 °C for 20-30 h to prepare CCNT-[MimAE]Cl; b) reacting CCNT-[MimAE]Cl with β-alanine APA at 60-70°C for 20-30 h in the presence of aqueous solvent, followed by filtering, washing, and drying to obtain CCNT-[MimAE][APA]; The preparation of MAO / PP / CCNT-[MimAE][APA] composite coating is specifically as follows: The magnesium alloy with the MAO coating on its surface is placed in a suction flask and vacuum-treated using a circulating water vacuum pump for 15-40 minutes. An anhydrous ethanol solution containing phenolphthalein PP is then added and vacuum-treated for 45-90 minutes. The mixture is then heated at 30-50°C for 3-5 hours and then air-dried at room temperature to obtain a MAO / PP composite coating. The prepared MAO / PP composite coating was placed in a suction filtration bottle, and a 90-110 mg / L anhydrous ethanol solution containing CCNT-[MimAE][APA] corrosion inhibitor was added. After continuing vacuum treatment for 45-90 min, the coating was heated at 30-50 °C for 3-5 h, taken out, and dried to obtain the MAO / PP / CCNT-[MimAE][APA] composite coating.

2. The method for preparing the intelligent anti-corrosion coating based on ionic liquid grafted carboxylated carbon nanotubes according to claim 1, characterized in that: In step a), the mass ratio of carboxylated carbon nanotubes CCNT and [MimAE]Cl is (0.7-0.9): (2.2-2.3).

3. The method for preparing the intelligent anti-corrosion coating based on ionic liquid grafted carboxylated carbon nanotubes according to claim 1, characterized in that: In step a), the molar ratio of β-alanine to CCNT-[MimAE]Cl is (0.9-1.1):(0.9-1.1).

4. The method for preparing the intelligent anti-corrosion coating based on ionic liquid grafted carboxylated carbon nanotubes according to claim 1, characterized in that: The concentration of the anhydrous ethanol solution containing phenolphthalein PP is 20-40 g / L.

5. The method for preparing the intelligent anti-corrosion coating based on ionic liquid grafted carboxylated carbon nanotubes according to claim 1, characterized in that: The specific steps of preparing the MAO coating on the surface of the magnesium alloy are as follows: the polished, cleaned and dried magnesium alloy sample is used as the anode, the stainless steel electrode is used as the cathode, and then placed in the electrolyte for MAO treatment to obtain a magnesium alloy with a MAO coating grown on the surface.

6. The method for preparing the intelligent anti-corrosion coating based on ionic liquid grafted carboxylated carbon nanotubes according to claim 5, characterized in that: The electrolyte composition is: 10-30 g / L sodium silicate, 5-20 g / L potassium hydroxide and 5-15 g / L potassium fluoride; the pulse current density of MAO treatment is 30-60 mA / cm 2 .

7. An intelligent anti-corrosion coating based on ionic liquid grafted carboxylated carbon nanotubes prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the intelligent anti-corrosion coating based on ionic liquid grafted carboxylated carbon nanotubes as claimed in claim 7 in metal corrosion self-reporting and corrosion prevention.

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