Carbon nanotube modified magnesium phosphate-based coating with both electric conduction and active corrosion prevention functions and preparation method thereof

Abstract

The application discloses a carbon nanotube modified magnesium phosphate-based paint with conductive and active corrosion prevention functions, and is characterized by comprising the following components: 40-55 parts of magnesium oxide, 5-10 parts of a retarder, 15-40 parts of water, 10-25 parts of a dihydrogen phosphate and 0.1-3.0 parts of functionalized carbon nanotubes. The functionalized carbon nanotubes are carbon nanotubes loaded with corrosion inhibitors, which are prepared by introducing oxygen-containing functional groups on the surface of the carbon nanotubes after acidification modification and then loading the corrosion inhibitors by vacuum impregnation. The application further discloses a preparation method of the carbon nanotube modified magnesium phosphate-based paint with conductive and active corrosion prevention functions. The oxygen-containing functional groups are introduced on the surface of the carbon nanotubes by acidification treatment, thus solving the agglomeration problem of the carbon nanotubes in the magnesium phosphate fast-setting system from the source, and the dispersion stability is significantly improved. The adsorption of the carbon nanotubes to the corrosion inhibitors is enhanced. The corrosion inhibitors are encapsulated on the surface and the lumen structure. When the coating is damaged in a severe environment such as seawater, the targeted release of the corrosion inhibitors can be triggered, and active corrosion prevention is achieved.

Description

Technical Field

[0001] This invention belongs to the field of multifunctional protective coating technology, and in particular relates to a carbon nanotube modified magnesium phosphate-based coating with both conductive and active anti-corrosion functions and its preparation method. Background Technology

[0002] Conductive coatings are functional materials that impart conductivity to coatings by introducing conductive fillers to construct a conductive network. They are widely used in electronic devices, electromagnetic shielding, antistatic applications, and engineering protection. Existing conductive coatings mainly include organic resin-based conductive coatings and inorganic cementitious material-based conductive coatings. Among them, inorganic conductive coatings have advantages such as high temperature resistance, aging resistance, corrosion resistance, and environmental friendliness, showing promising application prospects in complex service environments such as high temperature and strong corrosion.

[0003] Magnesium phosphate-based materials are a class of inorganic cementitious materials formed by the reaction of magnesium oxide and acidic phosphates. They possess characteristics such as rapid setting and hardening, high early strength, excellent adhesion to metal substrates, and resistance to high temperatures and chemical corrosion, making them widely used in the repair and protection of metal and concrete structures. However, magnesium phosphate-based materials are inherently electrical insulators, lacking effective electron transport channels, making them unsuitable for antistatic or conductive applications. To improve their conductivity, conductive fillers are typically introduced into the system to construct a conductive network.

[0004] Carbon nanotubes, due to their excellent electrical conductivity, high aspect ratio, and good mechanical properties, are considered ideal conductive fillers for constructing highly efficient conductive networks. Introducing carbon nanotubes into magnesium phosphate-based coating systems holds promise for imparting conductivity while maintaining the material's excellent protective properties. However, the following technical challenges remain in practical applications:

[0005] (1) The magnesium phosphate system has a fast reaction rate and short coagulation time. During the reaction, the system has a high ion concentration and a rapid increase in viscosity, which can easily lead to the aggregation of carbon nanotubes. It is difficult to uniformly disperse them in the matrix and form a continuous and stable conductive network, thus affecting the conductivity.

[0006] (2) In the prior art, in order to obtain a lower resistivity, it is usually necessary to increase the carbon nanotube content. Excessive carbon nanotube addition not only increases the material cost, but may also reduce the application performance of the coating and have an adverse effect on the mechanical properties and interfacial bonding performance of the coating.

[0007] (3) Existing research on magnesium phosphate-based conductive coatings mainly focuses on improving conductivity, while research on their long-term service performance in corrosive environments is relatively limited. Traditional magnesium phosphate protective coatings mainly rely on physical barriers to prevent the intrusion of corrosive media. When cracks, pores, or local damage occur in the coating, corrosive media may still penetrate into the metal substrate along the defect sites, causing local corrosion and thus reducing the long-term protective effect of the coating.

[0008] Especially in marine environments, high concentrations of chloride ions, salinity, and alternating hot and humid conditions further exacerbate metal corrosion. For applications requiring both conductivity and corrosion resistance, the introduction of a conductive network can alter the internal electrochemical behavior of the coating. However, current technologies lack magnesium phosphate-based conductive coating systems that can simultaneously achieve both conductivity and long-term corrosion resistance. Therefore, developing a magnesium phosphate-based conductive composite coating that can achieve uniform dispersion of conductive fillers and stable conductive network construction within a magnesium phosphate system while also improving the long-term corrosion resistance of the coating is of significant research importance and engineering application value. Summary of the Invention

[0009] To address the shortcomings of existing magnesium phosphate-based coatings, such as insufficient conductivity, limited functionality, lack of active corrosion protection, and the tendency for conductive fillers to aggregate and form stable, multifunctional networks in rapid reaction systems, this invention provides a carbon nanotube-modified magnesium phosphate-based coating and its preparation method, which combines conductivity and active corrosion protection. This invention innovatively functionalizes carbon nanotubes, solving their dispersibility issues, constructing a low-percolation-threshold conductive network, and endowing them with the ability to store and release corrosion inhibitors. The aim is to: pre-treat carbon nanotubes with acidification and load them with corrosion inhibitors, then introduce them into a magnesium phosphate matrix, allowing the carbon nanotubes to simultaneously serve as the framework of the conductive network and the carrier of the corrosion inhibitor within the matrix. This enables the controllability of the coating's conductivity and achieves long-lasting, active corrosion protection, overcoming the technical bottlenecks of existing conductive coatings that rely on passive barriers and have poor functional synergy.

[0010] The technical solution adopted by this invention to solve its technical problem is:

[0011] A carbon nanotube-modified magnesium phosphate-based coating with both conductive and active corrosion-resistant functions is characterized by comprising the following components: 40-55 parts magnesium oxide, 5-10 parts retarder, 15-40 parts water, 10-25 parts dihydrogen phosphate, and 0.1-3.0 parts functionalized carbon nanotubes. The functionalized carbon nanotubes are carbon nanotubes loaded with corrosion inhibitors, which are prepared by introducing oxygen-containing functional groups onto their surface through acid modification, followed by vacuum impregnation with the loaded corrosion inhibitor.

[0012] Preferably, the magnesium oxide is one or more of the following: dark-burned magnesium oxide and light-burned magnesium oxide.

[0013] Preferably, the magnesium oxide passes through a 200-mesh sieve.

[0014] Preferably, the retarder is one or more of borax, sodium phosphate, and citric acid.

[0015] Preferably, the dihydrogen phosphate is one or more of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, or sodium dihydrogen phosphate.

[0016] Preferably, the carbon nanotube is one or more of multi-walled carbon nanotubes, double-walled carbon nanotubes, or single-walled carbon nanotubes.

[0017] Preferably, the acidification modification involves acidifying and oxidizing the carbon nanotubes with one or more of nitric acid, sulfuric acid, and phosphoric acid to introduce one or more oxygen-containing functional groups, such as carboxyl, hydroxyl, and carbonyl, onto the surface of the carbon nanotubes.

[0018] Preferably, the corrosion inhibitor is one or more of zinc nitrate, lanthanum nitrate, or cerium nitrate.

[0019] This invention also provides a method for preparing a carbon nanotube-modified magnesium phosphate-based coating that combines electrical conductivity and active corrosion protection, comprising the following steps:

[0020] (1) Acidification treatment of carbon nanotubes

[0021] Carbon nanotubes are added to an acidification solution and acidified at 30-80°C for 0.5-3 hours. After washing, filtering and drying, acidified carbon nanotubes are obtained.

[0022] (2) Corrosion inhibitor loading

[0023] Acidified carbon nanotubes are dispersed in a corrosion inhibitor solution and ultrasonically treated in a vacuum environment for 1-3 hours to load the corrosion inhibitor onto the surface and cavity structure of the carbon nanotubes, thus obtaining functionalized carbon nanotubes.

[0024] (3) Preparation of magnesium phosphate-based coatings

[0025] Mix 40-55 parts of magnesium oxide, 5-10 parts of retarder, 15-40 parts of water and 10-25 parts of dihydrogen phosphate evenly, then add 0.1-3.0 parts of functionalized carbon nanotubes and stir thoroughly to form a modified magnesium phosphate-based coating.

[0026] (4) Coating and curing

[0027] The obtained coating is applied to the surface of a metal substrate by brushing, rolling, or spraying, and after curing at room temperature, it forms a composite coating that has both conductive and active anti-corrosion functions.

[0028] Unlike existing technologies that directly incorporate corrosion inhibitors into coating systems, the corrosion inhibitor in this invention is not dispersed freely in the magnesium phosphate matrix, but rather pre-loaded onto the surface and interior of the functionalized carbon nanotubes. During the acidification modification process, nitric acid, sulfuric acid, and phosphoric acid, or mixtures thereof, are used to treat the carbon nanotubes, causing selective oxidation of the surface and end defect sites. During oxidation, some carbon-carbon conjugated structures are opened, introducing oxygen-containing functional groups such as carboxyl, hydroxyl, and carbonyl groups onto the carbon nanotube surface, thereby increasing the surface polarity and hydrophilicity of the carbon nanotubes and improving their dispersion performance in aqueous systems. Simultaneously, these oxygen-containing functional groups can act as active sites, interacting with metal ions in the corrosion inhibitor. Coordination adsorption is formed through electrostatic adsorption and coordination bonding, which improves the loading efficiency and stability of corrosion inhibitors on the surface and cavity structure of carbon nanotubes.

[0029] When the coating is intact, the corrosion inhibitor loaded on the carbon nanotubes is confined to the surface and inside the cavity of the carbon nanotubes, and the release rate is low. Therefore, it will not undergo continuous dissolution and loss in the early stage of service like traditional incorporated corrosion inhibitors, thus significantly improving the utilization efficiency of corrosion inhibitors and the service life of the coating.

[0030] When the coating is subjected to mechanical damage, cracks, pinholes, or localized corrosion, the corrosive medium preferentially penetrates into the coating along the defect area and comes into contact with the functionalized carbon nanotubes near the defect. Under the influence of moisture, excess magnesium oxide in the coating in the defect area continues to undergo hydration, causing a local pH increase; simultaneously, chloride ions and other substances in the corrosive medium alter the local ionic environment. These changes in the corrosive microenvironment and electrochemical conditions lead to a decrease in the adsorption capacity of the corrosion inhibitor. Therefore, the corrosion inhibitor on the surface and in the lumen of the carbon nanotubes is gradually released and migrates to the metal corrosion-active area, forming a protective passivation film or adsorption protective layer on the metal surface, thereby inhibiting anodic dissolution and cathodic reactions, achieving active protection of the defect area.

[0031] Therefore, this invention integrates the carbon nanotube conductive network and corrosion inhibitor reservoir, enabling the carbon nanotubes to simultaneously function as a conductive framework and corrosion inhibitor carrier. Compared to traditional incorporated corrosion inhibitor systems, this invention achieves directional storage and corrosion-triggered release of the corrosion inhibitor. In non-corrosive areas, the corrosion inhibitor release is slow due to coordination adsorption, while in damaged or corroded areas, the release of the corrosion inhibitor is accelerated, thereby significantly reducing ineffective consumption of the corrosion inhibitor, improving the utilization rate of the corrosion inhibitor, and enhancing the long-term anti-corrosion performance of the coating.

[0032] The beneficial effects of this invention are: (1) By introducing oxygen-containing functional groups on the surface of carbon nanotubes through acidification treatment, the problem of agglomeration in the magnesium phosphate fast-setting system is solved from the source, significantly improving the dispersion stability; and the adsorption capacity of carbon nanotubes for corrosion inhibitors is greatly enhanced. (2) Unlike traditional physical blending, this invention encapsulates the corrosion inhibitor in the surface and cavity structure. When the coating is damaged in harsh environments such as seawater, the corrosion inhibitor can be triggered to release in a targeted manner, achieving active corrosion protection. No substrate corrosion was found in the damaged area after 1000 hours in a neutral salt spray test environment. (3) The modified carbon nanotubes can construct a continuous three-dimensional conductive network with a low addition amount (0.1~3.0 parts), and the surface resistivity can be as low as 10. 2 ~10 8 Within the Ω range, a single coating can simultaneously possess excellent conductivity and long-lasting active corrosion protection. (4) The coating is applied to the surface of the metal substrate by brushing, rolling or spraying, and the construction operation is simple. Attached Figure Description

[0033] Figure 1 The corrosion of Examples 1-3 and Comparative Examples 1-3 after 1000 h of neutral salt spray is shown.

[0034] Figure 2 This is a transmission electron microscope (TEM) image of the functionalized carbon nanotubes of this invention. Detailed Implementation

[0035] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0036] Example 1:

[0037] Includes the following steps:

[0038] (1) Acidification treatment of carbon nanotubes

[0039] Multi-walled carbon nanotubes were added to a nitric acid solution and acidified at 35°C for 3 hours. After washing, filtering and drying, acidified carbon nanotubes were obtained.

[0040] (2) Corrosion inhibitor loading

[0041] Acidified carbon nanotubes were dispersed in zinc nitrate solution and ultrasonically treated in a vacuum environment for 1 h to load zinc nitrate onto the surface and cavity structure of carbon nanotubes, thus obtaining functionalized carbon nanotubes.

[0042] (3) Preparation of magnesium phosphate-based coatings

[0043] After mixing 30 parts of recalcined magnesium oxide, 23 parts of lightly calcined magnesium oxide, 4 parts of borax, 3 parts of citric acid, 15 parts of water, and 25 parts of potassium dihydrogen phosphate evenly, add 0.1 parts of functionalized carbon nanotubes and stir thoroughly to form a modified magnesium phosphate-based coating.

[0044] (4) Coating and curing

[0045] The obtained coating is applied to the surface of a metal substrate by spraying and cured at room temperature to form a composite coating that has both conductive and active anti-corrosion functions.

[0046] Example 2:

[0047] Includes the following steps:

[0048] (1) Acidification treatment of carbon nanotubes

[0049] Multi-walled carbon nanotubes and single-walled carbon nanotubes were added to a mixed solution of nitric acid and sulfuric acid at a mass ratio of 1:2, and acidified at 75°C for 1 h. After washing, filtering and drying, acidified carbon nanotubes were obtained.

[0050] (2) Corrosion inhibitor loading

[0051] Acidified carbon nanotubes were dispersed in a mixed solution of zinc nitrate and lanthanum nitrate, and ultrasonically treated in a vacuum environment for 2 h to load zinc nitrate and lanthanum nitrate onto the surface and cavity structure of carbon nanotubes, thus obtaining functionalized carbon nanotubes.

[0052] (3) Preparation of magnesium phosphate-based coatings

[0053] Mix 50 parts of recalcined magnesium oxide, 5 parts of borax, 5 parts of sodium phosphate, 30 parts of water, 5 parts of potassium dihydrogen phosphate, and 5 parts of ammonium dihydrogen phosphate evenly, then add 1.5 parts of functionalized carbon nanotubes and stir thoroughly to form a modified magnesium phosphate-based coating.

[0054] (4) Coating and curing

[0055] The obtained coating is applied to the surface of a metal substrate by roller coating and cured at room temperature to form a composite coating with both conductive and active anti-corrosion functions.

[0056] Example 3:

[0057] Includes the following steps:

[0058] (1) Acidification treatment of carbon nanotubes

[0059] Multi-walled carbon nanotubes, double-walled carbon nanotubes and single-walled carbon nanotubes were added to a mixed solution of sulfuric acid and phosphoric acid in a mass ratio of 1:1:1. The solution was acidified at 45°C for 2 h. After washing, filtering and drying, acidified carbon nanotubes were obtained.

[0060] (2) Corrosion inhibitor loading

[0061] Acidified carbon nanotubes were dispersed in a mixed solution of zinc nitrate and cerium nitrate, and ultrasonically treated in a vacuum environment for 3 h to load zinc nitrate and cerium nitrate onto the surface and cavity structure of carbon nanotubes, thus obtaining functionalized carbon nanotubes.

[0062] (3) Preparation of magnesium phosphate-based coatings

[0063] After mixing 43 parts of lightly calcined magnesium oxide, 5 parts of citric acid, 35 parts of water, 5 parts of potassium dihydrogen phosphate, 5 parts of ammonium dihydrogen phosphate, and 7 parts of sodium dihydrogen phosphate evenly, 3.0 parts of functionalized carbon nanotubes are added and stirred thoroughly to form a modified magnesium phosphate-based coating.

[0064] (4) Coating and curing

[0065] The obtained coating is applied to the surface of a metal substrate by brushing and cured at room temperature to form a composite coating that has both conductive and active anti-corrosion functions.

[0066] Comparative Example 1:

[0067] Includes the following steps:

[0068] (1) Acidification treatment of carbon nanotubes

[0069] Do not perform this step;

[0070] (2) Corrosion inhibitor loading

[0071] Multi-walled carbon nanotubes, double-walled carbon nanotubes, and single-walled carbon nanotubes (mass ratio 1:1:1) were dispersed in a mixed solution of zinc nitrate and cerium nitrate, and ultrasonically treated under vacuum for 3 h to obtain carbon nanotube A.

[0072] (3) Preparation of magnesium phosphate-based coatings

[0073] After mixing 43 parts of lightly calcined magnesium oxide, 5 parts of citric acid, 35 parts of water, 5 parts of potassium dihydrogen phosphate, 5 parts of ammonium dihydrogen phosphate, and 7 parts of sodium dihydrogen phosphate evenly, add 3.0 parts of carbon nanotubes A and stir thoroughly to form a magnesium phosphate-based coating.

[0074] (4) Coating and curing

[0075] The obtained coating is applied to the surface of a metal substrate by brushing and cured at room temperature.

[0076] Comparative Example 2:

[0077] Includes the following steps:

[0078] (1) Acidification treatment of carbon nanotubes

[0079] Multi-walled carbon nanotubes, double-walled carbon nanotubes and single-walled carbon nanotubes were added to a mixed solution of sulfuric acid and phosphoric acid in a mass ratio of 1:1:1. The solution was acidified at 45°C for 2 h. After washing, filtering and drying, acidified carbon nanotubes were obtained.

[0080] (2) Corrosion inhibitor loading

[0081] Do not perform this step;

[0082] (3) Preparation of magnesium phosphate-based coatings

[0083] After mixing 43 parts of lightly calcined magnesium oxide, 5 parts of citric acid, 35 parts of water, 5 parts of potassium dihydrogen phosphate, 5 parts of ammonium dihydrogen phosphate, and 7 parts of sodium dihydrogen phosphate evenly, 3.0 parts of acidified carbon nanotubes are added and stirred thoroughly to form a magnesium phosphate-based coating.

[0084] (4) Coating and curing

[0085] The obtained coating is applied to the surface of a metal substrate by brushing and cured at room temperature.

[0086] Comparative Example 3:

[0087] Includes the following steps:

[0088] (1) Acidification treatment of carbon nanotubes

[0089] Do not perform this step;

[0090] (2) Corrosion inhibitor loading

[0091] Do not perform this step;

[0092] (3) Preparation of magnesium phosphate-based coatings

[0093] Mix 43 parts of lightly calcined magnesium oxide, 5 parts of citric acid, 17 parts of water, 5 parts of potassium dihydrogen phosphate, 5 parts of ammonium dihydrogen phosphate, and 7 parts of sodium dihydrogen phosphate evenly and stir thoroughly to form a magnesium phosphate-based coating.

[0094] (4) Coating and curing

[0095] The obtained coating is applied to the surface of a metal substrate by brushing and cured at room temperature.

[0096] To verify the effectiveness of the present invention, the following experiments were conducted.

[0097] (1) Coating conductivity

[0098] To measure the surface resistivity of the coating, two copper conductive strips were attached to the coating surface (2 cm apart, 5 cm long). The current-time response was recorded using an electrochemical workstation under constant potential polarization of 100 mV, and the surface resistivity was calculated using formula (1).

[0099] (1)

[0100] In the formula: Rs is the surface resistivity in Ω; W is the width of the conductive adhesive in 5 cm; D is the spacing between the conductive adhesives in 2 cm; U is the test voltage in 0.1 V; and I is the output current in A.

[0101] The surface resistivity of Examples 1-3 and Comparative Examples 1-3 was calculated using the above formulas, as shown in Table 1.

[0102] Table 1. Electrical conductivity of the coating

[0103]

[0104] As can be seen from Table 1, the surface resistivity of Comparative Example 3, which did not contain any carbon nanotubes, was as high as 4.60 × 10⁻⁶. 9 Ω. After adding carbon nanotubes, the surface conductivity of the coatings in Examples 1-3 steadily increased with the increase of functionalized carbon nanotube doping. Comparing Example 3 with Comparative Example 1, it can be seen that the surface resistivity of the coating with acidified carbon nanotubes is much lower than that of the coating with un-acidified carbon nanotubes. This indicates that acidification treatment improves the carbon nanotube aggregation problem, the filler is more uniformly dispersed in the magnesium phosphate coating matrix, and it is easier to build a continuous conductive network, resulting in significantly better conductivity than un-acidified carbon nanotubes. Furthermore, as shown in Comparative Example 2, acidification of carbon nanotubes without corrosion inhibitors can still achieve good conductivity.

[0105] (2) Corrosion resistance of the coating

[0106] The long-term protective stability of the coating in a chloride-salt environment was evaluated using a neutral salt spray test. The test was conducted according to ASTM B117, "Standard Practice for Operating Salt Spray (Fog) Apparatus". A 5.0% NaCl solution was used, with the pH of the salt solution controlled between 6.5 and 7.2, and the test chamber temperature set at 35 °C. Before the test, scratches were created on the coating using a scribe bar, and the corrosion test lasted 1000 hours. The test results are as follows: Figure 1 As shown.

[0107] from Figure 1 As can be seen, after artificially created scratch defects and 1000 hours of neutral salt spray testing, no obvious signs of corrosion were observed in Experiments 1-3. This indicates that when the salt spray corrosive medium reaches the substrate surface along the scratches, for carbon nanotube-modified magnesium phosphate coatings, the functionalized carbon nanotubes (such as...) Figure 2The corrosion inhibitor sealed in the carbon nanotubes can be released at the scratches, further forming a passivation film on the steel plate surface, achieving active corrosion protection. Comparative Example 1, which incorporated carbon nanotubes with only the corrosion inhibitor, showed slight corrosion. Although the corrosion inhibitor had an inhibitory effect, it was inferior to Examples 1-3, indicating that the acid treatment of the carbon nanotubes had a beneficial effect on the loading and release of the corrosion inhibitor. Comparative Example 2, which incorporated only acid-treated carbon nanotubes, and Comparative Example 3, which did not contain any carbon nanotubes, both showed severe corrosion. These comparisons demonstrate that the carbon nanotube-modified magnesium phosphate coating of the present invention has excellent anti-corrosion effects.

[0108] The above specific embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A carbon nanotube-modified magnesium phosphate-based coating with both conductive and active anti-corrosion functions, characterized in that, The product comprises the following components: 40-55 parts magnesium oxide, 5-10 parts retarder, 15-40 parts water, 10-25 parts dihydrogen phosphate, and 0.1-3.0 parts functionalized carbon nanotubes. The functionalized carbon nanotubes are carbon nanotubes loaded with corrosion inhibitors, which are prepared by introducing oxygen-containing functional groups onto their surface through acid modification, followed by vacuum impregnation with the loaded corrosion inhibitor.

2. The carbon nanotube-modified magnesium phosphate-based coating with both conductive and active anti-corrosion functions according to claim 1, characterized in that: The magnesium oxide is one or more of the following: dark-burned magnesium oxide and light-burned magnesium oxide.

3. The carbon nanotube-modified magnesium phosphate-based coating with both conductive and active anti-corrosion functions according to claim 1, characterized in that: The retarder is one or more of borax, sodium phosphate, and citric acid.

4. The carbon nanotube-modified magnesium phosphate-based coating with both conductive and active anti-corrosion functions according to claim 1, characterized in that: The dihydrogen phosphate is one or more of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, or sodium dihydrogen phosphate.

5. The carbon nanotube-modified magnesium phosphate-based coating with both conductive and active anti-corrosion functions according to claim 1, characterized in that: The carbon nanotubes are one or more of multi-walled carbon nanotubes, double-walled carbon nanotubes, or single-walled carbon nanotubes.

6. The carbon nanotube-modified magnesium phosphate-based coating with both conductive and active anti-corrosion functions according to claim 1, characterized in that: The acidification modification involves acidifying and oxidizing carbon nanotubes with one or more of nitric acid, sulfuric acid, and phosphoric acid to introduce one or more oxygen-containing functional groups, such as carboxyl, hydroxyl, and carbonyl, onto the surface of the carbon nanotubes.

7. The carbon nanotube-modified magnesium phosphate-based coating with both conductive and active anti-corrosion functions according to claim 1, characterized in that: The corrosion inhibitor is one or more of zinc nitrate, lanthanum nitrate, or cerium nitrate.

8. The carbon nanotube-modified magnesium phosphate-based coating with both conductive and active anti-corrosion functions according to claim 2, characterized in that: The magnesium oxide passed through a 200-mesh sieve.

9. A method for preparing a carbon nanotube-modified magnesium phosphate-based coating with both conductive and active anti-corrosion functions as described in any one of claims 1-8 comprises the following steps: (1) Acidification treatment of carbon nanotubes Carbon nanotubes are added to an acidification solution and acidified at 30-80°C for 0.5-3 hours. After washing, filtering and drying, acidified carbon nanotubes are obtained. (2) Corrosion inhibitor loading Acidified carbon nanotubes are dispersed in a corrosion inhibitor solution and ultrasonically treated in a vacuum environment for 1-3 hours to load the corrosion inhibitor onto the surface and cavity structure of the carbon nanotubes, thus obtaining functionalized carbon nanotubes. (3) Preparation of magnesium phosphate-based coatings Mix 40-55 parts of magnesium oxide, 5-10 parts of retarder, 15-40 parts of water and 10-25 parts of dihydrogen phosphate evenly, then add 0.1-3.0 parts of functionalized carbon nanotubes and stir thoroughly to form a modified magnesium phosphate-based coating. (4) Coating and curing The obtained coating is applied to the surface of a metal substrate by brushing, rolling, or spraying, and after curing at room temperature, it forms a composite coating that has both conductive and active anti-corrosion functions.

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