A preparation method of a BTA-ZIF-8@Ce-MMT nanocomposite powder with double corrosion inhibitors

Abstract

This invention relates to metal protective coating material technology, aiming to provide a method for preparing BTA-ZIF-8@Ce-MMT nanocomposite powder supported by dual corrosion inhibitors. MMT particles, after ball milling, are ultrasonically dispersed in water, and the supernatant is collected after natural sedimentation. Cerium nitrate hexahydrate and an appropriate amount of deionized water are added, and the mixture is reacted at 25°C with stirring for 24 hours. Zinc nitrate hexahydrate is then added and stirred until completely dissolved. A mixed solution of benzotriazole (BTA), 2-methylimidazole, and anhydrous ethanol is then added, and the mixture is reacted at 25°C with stirring for 12 hours. The reaction solution is centrifuged, and the precipitate is washed and dried to obtain the nanocomposite powder. This product can simultaneously inhibit corrosion in both the anodic and cathodic regions of the corrosion reaction micro-zone, further improving the active protection effect. The reaction only requires room temperature conditions, simplifying the synthesis process. The powder exhibits good dispersibility in water-based epoxy coatings and is not prone to agglomeration. This method reduces preparation costs and broadens the application range of rare earth elements.

Description

Technical Field

[0001] This invention relates to the field of metal protective coating materials technology, and in particular to a method for preparing BTA-ZIF-8@Ce-MMT nanocomposite powder supported by dual corrosion inhibitors, which aims to impart active protective function to waterborne epoxy coatings. Background Technology

[0002] Metal corrosion is a major threat to the safety and lifespan of infrastructure, and the economic losses caused by it are substantial. Epoxy resin coatings, as a primary technology for metal protection, rely on a passive protection mechanism, delaying corrosion by forming a physical barrier between the metal surface and the corrosive environment. However, water-based epoxy coatings often develop surface defects during curing and use, leading to the penetration of corrosive media, which in turn triggers localized corrosion reactions and ultimately results in the loss of protective efficacy. Therefore, in recent years, coating technology has gradually incorporated active protection mechanisms, effectively extending the service life of coatings by adding corrosion inhibitors. When the coating is damaged or corrosion occurs on the metal surface, corrosion inhibitors can passivate the metal surface or delay the corrosion reaction, thereby enhancing the coating's self-healing ability and significantly improving its service life.

[0003] Montmorillonite (MMT) is a natural silicate mineral widely used in adsorbent materials, catalyst supports, and drug delivery systems due to its layered structure, excellent ion exchange capacity, and abundant resources. In the field of metal protection, montmorillonite is commonly used as a coating filler to enhance the barrier properties of polymer coatings. However, because montmorillonite has a high polarity due to its rich hydroxyl content and poor compatibility with organic polymers, surface modification is usually required to enhance its corrosion protection performance in coatings. Currently, research on the application of montmorillonite as a coating filler in active protection is still in its infancy in both academia and industry.

[0004] Benzotriazole (BTA) is a commonly used corrosion inhibitor widely applied in metal protective coatings. It effectively slows down metal corrosion by forming stable complexes with metal ions. However, the amount of benzotriazole added is generally small (0.1–1%), as excessive addition can easily lead to agglomeration during the coating curing process, thus reducing the coating's corrosion resistance.

[0005] Therefore, it is necessary to propose new solutions to address the aforementioned technical problems. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing BTA-ZIF-8@Ce-MMT nanocomposite powder supported by dual corrosion inhibitors.

[0007] To solve the technical problem, the solution of the present invention is:

[0008] A method for preparing dual corrosion inhibitor-supported BTA-ZIF-8@Ce-MMT nanocomposite powder is provided, comprising the following steps:

[0009] (1) Take dry montmorillonite, and ball mill it to obtain MMT particles;

[0010] (2) Add an appropriate amount of deionized water to the MMT particles from step (1), disperse by ultrasonication, and allow to settle naturally; take the supernatant for later use.

[0011] (3) Add cerium nitrate hexahydrate and an appropriate amount of deionized water to the supernatant of step (2) and react for 24 hours in a water bath at 25°C with stirring.

[0012] (4) Add zinc nitrate hexahydrate to the reaction solution obtained in step (3) and stir until completely dissolved;

[0013] (5) Add benzotriazole BTA and 2-methylimidazole to an appropriate amount of anhydrous ethanol and stir until completely dissolved;

[0014] (6) Mix the two solutions obtained in step (4) and step (5), and then react them for 12 hours in a water bath at 25°C with stirring.

[0015] (7) The reaction solution obtained in step (6) is centrifuged and separated. After centrifugation, washing and drying of the precipitate, BTA-ZIF-8@Ce-MMT nanocomposite powder is obtained.

[0016] The mass ratio of montmorillonite (MMT), cerium nitrate hexahydrate, zinc nitrate hexahydrate, benzotriazole (BTA), and 2-methylimidazole used in the above steps is 6–10: 0.1–0.2: 0.5–1.5: 0.3–0.96: 1–2.85.

[0017] As a preferred embodiment of the present invention, based on 6-10 parts by weight of montmorillonite (MMT), the amount of deionized water added in step (2) is 120-150 parts by weight, and 10-20 parts by weight of the supernatant is taken; the amount of deionized water added in step (3) is 75-90 parts by weight; and the amount of anhydrous ethanol added in step (5) is 25-40 parts by weight.

[0018] As a preferred embodiment of the present invention, in step (1), the ball milling time is 2 hours, the frequency of the drive motor is 45Hz, and the rotation speed of the ball mill is 2700rpm.

[0019] As a preferred embodiment of the present invention, in step (2), the ultrasonic dispersion is performed for 20 minutes, and the natural sedimentation is performed for 24 hours, so that the size of the MMT particles in the supernatant is ≤1μm.

[0020] As a preferred embodiment of the present invention, the purity of cerium nitrate hexahydrate, zinc nitrate hexahydrate, benzotriazole BTA, 2-methylimidazole and anhydrous ethanol is not less than 99.7%.

[0021] As a preferred embodiment of the present invention, the stirring speed in steps (3) to (6) is 750 rpm.

[0022] As a preferred embodiment of the present invention, in step (7), the centrifugal separation speed is at least 5000 rpm and the time is at least 15 min; the centrifugal washing speed is at least 5000 rpm and the time is at least 15 min; the drying treatment is drying in an oven at 60°C.

[0023] The present invention further provides a method for applying the dual corrosion inhibitor-loaded BTA-ZIF-8@Ce-MMT nanocomposite powder prepared by the aforementioned method. The method involves adding the nanocomposite powder to a waterborne epoxy resin anticorrosive coating, wherein the mass ratio of the nanocomposite powder to the waterborne epoxy resin anticorrosive coating is 0.5%. After stirring evenly, the mixed coating is applied to the substrate surface by spraying or coating. The coating is then cured at 150°C for 1 hour to obtain a waterborne epoxy resin anticorrosive coating with active protective function.

[0024] Description of the invention principle:

[0025] 1. Montmorillonite possesses excellent cation intercalation characteristics, enabling it to incorporate corrosion inhibitors into the interlayer. Utilizing this characteristic to prepare nanocomposite powders not only provides passive barrier functions but also active protection. Chromium-containing corrosion inhibitors have significant effects in metal protection, but their toxicity limits their application. Cerium ions and their compounds are considered environmentally friendly alternatives to chromates, providing cathodic protection by reacting with hydroxide ions to form protective films of cerium oxides and hydroxides. Cerium's abundant reserves and low cost offer broad prospects for its application in the field of protection. Based on the above factors, this invention utilizes inexpensive and abundant montmorillonite raw material loaded with cerium ions and benzotriazole dual corrosion inhibitors. Through the cationic substitution properties of montmorillonite, environmentally friendly cerium ions are introduced into the interlayer structure of the montmorillonite nanosheets. Simultaneously, an in-situ growth method is used to construct a zeolite imidazole ester metal-organic framework material (BTA-ZIF-8) coated with benzotriazole on the surface of the montmorillonite nanosheets. Nanocomposite powder preparation technology effectively improves the compatibility of the filler nanocomposite powder with waterborne epoxy coatings, achieving a nanocomposite powder with both active protection and passive barrier functions. This powder is then added in trace amounts to waterborne epoxy protective coatings to improve coating performance.

[0026] The dual corrosion inhibitor mentioned in this invention refers to benzotriazole and cerium ions.

[0027] 2. Montmorillonite (MMT) is a natural silicate clay mineral with a layered structure. It consists of two layers of silicon-oxygen tetrahedra sandwiching aluminum-oxygen octahedra and possesses exchangeable interlayer cations. Due to its abundant natural resources, montmorillonite is inexpensive. Its two-dimensional layered structure effectively acts as a barrier against corrosive media in coatings; however, its high surface polarity and large particle size result in poor compatibility with organic polymers.

[0028] Zeolite imidazole ester framework material (ZIF-8) is a metal-organic framework (MOF) with tunable pore size, low toxicity, good chemical stability, and acid sensitivity, and is widely used in biomedicine, wastewater treatment, catalysts, and protection. Due to differences in application methods, there are currently no publicly available records of combining ZIF-8 with montmorillonite.

[0029] This invention involves ball milling montmorillonite with BTA-loaded ZIF-8 nanoparticles to construct a nanocomposite powder. The one-step in-situ synthesis of ZIF-8 particles on montmorillonite not only endows the composite material with both active protection and passive barrier functions, but also improves the surface polarity of montmorillonite and increases its specific surface area through the growth of ZIF-8 particles, thereby enhancing its compatibility with organic polymers. This method is unprecedented in the field.

[0030] 3. This invention innovatively proposes to introduce cerium ions, which have corrosion-inhibiting functions, as guest elements into the interlayer of montmorillonite particles via cation exchange, thus obtaining Ce-MMT two-dimensional materials. Cerium is one of the most abundant rare earth elements in the Earth's crust, making it a rich resource. Inserting cerium ions into the montmorillonite interlayer through cation exchange not only endows it with active protection but also provides cathodic protection when corrosive media erode the substrate. The preparation process of this invention is simple, requiring only room-temperature stirring, greatly reducing energy consumption. Furthermore, the raw materials are abundant and inexpensive, and no toxic substances are generated during the preparation process, meeting green and environmentally friendly requirements.

[0031] 4. This invention innovatively incorporates the corrosion inhibitor BTA molecule as a second ligand within the ZIF-8 framework structure, giving it pH-responsive functionality and enabling controlled release of the corrosion inhibitor. This avoids the problem of corrosion inhibitors being directly introduced into the protective coating, leading to a decline in coating performance. Furthermore, the modification of the ZIF-8 microsphere surface with montmorillonite two-dimensional nanosheets improves the compatibility between the powder and the coating, achieving uniform distribution within the coating and filling voids and pores caused by solvent evaporation during the curing of waterborne epoxy resin, thus reducing the formation of microcracks and defects in the coating.

[0032] 5. The active defense mechanism of the product at the microscopic level is as follows:

[0033] As the service life of waterborne epoxy protective coatings increases, defects such as cracks and micropores on the coating surface increase, forming corrosion channels and accelerating the intrusion of corrosive media. The two-dimensional structure of montmorillonite in the nanocomposite powder can extend the diffusion path of corrosive media, playing a passive protective role. Simultaneously, when corrosion reaches the metal surface, the triggered micro-area electrochemical reaction causes a decrease in the pH value of the anodic region, prompting the collapse of the ZIF-8 framework and releasing BTA molecules to complex with iron ions, forming an inhibitory film to prevent further corrosion of the metal surface. Furthermore, hydroxide ions in the cathodic region react with cerium ions to form cerium hydroxide or cerium oxide deposition films, thus providing active protection.

[0034] In practical applications, this is achieved by adding 0.5% by mass of BTA-ZIF-8@Ce-MMT nanocomposite powder to a water-based epoxy coating and spraying it onto a metal substrate, thus achieving both active and passive protection. Therefore, this invention breaks through the traditional approach of using separate two-dimensional materials and core-shell structured nanocomposite components.

[0035] Compared with other existing types of waterborne epoxy coating active protective materials, the present invention has the following advantages:

[0036] 1. The nanocomposite powder prepared by the technology of this invention is loaded with cerium ions and benzotriazole dual corrosion inhibitor, which can simultaneously achieve corrosion inhibition in the anodic and cathodic regions of the corrosion reaction micro-region, further improving the active protection effect of the powder.

[0037] 2. In the preparation process of this invention, the required reaction conditions are all at room temperature. By utilizing the characteristics of the raw materials, the final nanocomposite powder is synthesized in situ through cation exchange and one-step method. No additional reaction conditions or loading steps such as heating and pressurization are required, which simplifies the synthesis process.

[0038] 3. The nanocomposite powder prepared by this invention has good dispersibility in water-based epoxy coatings and is not prone to agglomeration, thus expanding the application scope of montmorillonite two-dimensional sheet materials in the field of protection.

[0039] 4. The montmorillonite and cerium used in this invention are both natural mineral resources with relatively abundant reserves, which reduces the preparation cost and broadens the application range of rare earth elements. Attached Figure Description

[0040] Figure 1 This is a scanning electron microscope (5000x) image of montmorillonite (MMT) in the supernatant after ball milling and natural sedimentation in deionized water.

[0041] Figure 2 This is a scanning electron microscope image (20,000x) of BTA-ZIF-8@Ce-MMT nanocomposite powder.

[0042] Figure 3 This is the nitrogen adsorption-desorption curve of BTA-ZIF-8@Ce-MMT nanocomposite powder.

[0043] Figure 4 This is a pore size distribution diagram of BTA-ZIF-8@Ce-MMT nanocomposite powder.

[0044] Figure 5 This is a release curve of BTA, the corrosion inhibitor of BTA-ZIF-8@Ce-MMT nanocomposite powder, at different times and pH values.

[0045] Figure 6 This is a graph showing the release concentration of cerium ions, the corrosion inhibitor of BTA-ZIF-8@Ce-MMT nanocomposite powder, at different time points and pH values.

[0046] Figure 7 Electrochemical impedance spectroscopy (EIS) spectra of waterborne epoxy protective coatings with no corrosion inhibitor, 0.5% MMT, and 0.5% BTA-ZIF-8@Ce-MMT nanocomposite powder, respectively, after immersion in 3.5% NaCl solution for 28 days.

[0047] Figure 8 The images show the adhesion changes of water-based epoxy protective coatings with and without corrosion inhibitors, with and without 0.5% MMT, and with 0.5% BTA-ZIF-8@Ce-MMT nanocomposite powder, before and after immersion in a salt spray chamber for two weeks. Detailed Implementation

[0048] The present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0049] 1. Overview of the implementation schemes of the present invention:

[0050] Preparation steps of dual corrosion inhibitor-supported BTA-ZIF-8@Ce-MMT nanocomposite powder:

[0051] (1) Take dry montmorillonite and ball mill it to obtain MMT particles; as an example, the ball milling time is 2 hours, the frequency of the drive motor is 45Hz, and the speed of the ball mill is 2700rpm.

[0052] (2) Add an appropriate amount of deionized water to the MMT particles from step (1), ultrasonically disperse for 20 minutes, and allow to settle naturally for 24 hours. Take the supernatant for later use; the MMT particle size in the supernatant should be ≤1μm.

[0053] Through steps (1) and (2), montmorillonite is made to exhibit a more two-dimensional layered structure, creating conditions for subsequent cerium ion replacement and in-situ growth to prepare metal-organic framework materials. The supernatant is taken because large-sized montmorillonite will settle, and the montmorillonite particles contained in the supernatant are smaller in size, which is more conducive to the subsequent dispersion of particles in water-based epoxy coatings.

[0054] (3) Add cerium nitrate hexahydrate and an appropriate amount of deionized water to the supernatant of step (2) and react for 24 hours in a water bath at 25°C with stirring.

[0055] Through this step, due to the excellent cation exchange properties of montmorillonite, cerium ions are replaced into the interlayer of montmorillonite through ion exchange reaction, which promotes the addition of the first corrosion inhibitor, cerium ions, into the particles.

[0056] (4) Add zinc nitrate hexahydrate to the reaction solution obtained in step (3) and stir until completely dissolved;

[0057] (5) Add benzotriazole BTA and 2-methylimidazole to an appropriate amount of anhydrous ethanol and stir until completely dissolved;

[0058] (6) Mix the two solutions obtained in step (4) and step (5), and then react them for 12 hours in a water bath at 25°C with stirring.

[0059] Through steps (4), (5), and (6), a MOF structure ZIF-8 with zinc ions and imidazole ligands was synthesized in one step on the layered structure of montmorillonite, and a second corrosion inhibitor, benzotriazole, was directly added in the form of the second ligand.

[0060] (7) The reaction solution obtained in step (6) is centrifuged and separated. After centrifugation, washing and drying of the precipitate, BTA-ZIF-8@Ce-MMT nanocomposite powder is obtained. The centrifugation speed is at least 5000 rpm and the time is at least 15 min. The centrifugation washing speed is at least 5000 rpm and the time is at least 15 min. The drying treatment is carried out in an oven at 60℃.

[0061] This step yields dried powder of the final particles BTA-ZIF-8@Ce-MMT, preparing it for subsequent spraying in waterborne epoxy coatings.

[0062] The mass ratio of montmorillonite (MMT), cerium nitrate hexahydrate, zinc nitrate hexahydrate, benzotriazole (BTA), and 2-methylimidazole used in the above steps is 6–10: 0.1–0.2: 0.5–1.5: 0.3–0.96: 1–2.85. Based on 6–10 parts by mass of montmorillonite (MMT), 120–150 parts by mass of deionized water are added in step (2), and 10–20 parts by mass of the supernatant are taken; 75–90 parts by mass of deionized water are added in step (3); and 25–40 parts by mass of anhydrous ethanol are added in step (5). The purity of cerium nitrate hexahydrate, zinc nitrate hexahydrate, benzotriazole (BTA), 2-methylimidazole, and anhydrous ethanol is not less than 99.7%. In steps (3) to (6), the stirring speed is 750 rpm.

[0063] 2. Application method of dual corrosion inhibitor-supported BTA-ZIF-8@Ce-MMT nanocomposite powder:

[0064] (1) The nanocomposite powder is added to the water-based epoxy resin anticorrosive coating and stirred evenly for later use. The mass ratio of the nanocomposite powder to the water-based epoxy resin anticorrosive coating is 0.5%.

[0065] (2) Apply the mixed coating to the substrate surface by spraying or coating; cure at 150°C for 1 hour to obtain a water-based epoxy resin anti-corrosion coating with active protection function.

[0066] The thickness of the coating, whether sprayed or coated, can be determined based on the requirements of the actual application scenario and the characteristics of the water-based epoxy resin anti-corrosion coating itself.

[0067] 2. Implementation Examples

[0068] In the following examples, the montmorillonite used was a product of Shanghai Maclean Biochemical Technology Co., Ltd., benzotriazole and 2-methylimidazole were products of Aladdin Industrial Co., Ltd., and anhydrous ethanol, zinc nitrate hexahydrate, and cerium nitrate hexahydrate were products of Sinopharm Chemical Reagent Co., Ltd. The bentonite particle size was ≤25μm, the purity of BTA was at least 99%, the purity of 2-methylimidazole was at least 98%, the purity of anhydrous ethanol was at least 99.7%, the purity of zinc nitrate hexahydrate was at least 99%, and the purity of cerium nitrate hexahydrate was at least 99%.

[0069] Unless otherwise specified, all percentages below are by weight, and all numbers are by weight. Operating conditions not described in the embodiments shall be performed as described in the previous implementation overview.

[0070] Example 1

[0071] (1) Six parts by weight of dried montmorillonite were ball-milled for 2 hours to obtain montmorillonite particles;

[0072] (2) Add 120 parts by mass of deionized water to the montmorillonite particles in step (1), disperse ultrasonically for 20 minutes, and allow to settle naturally for 24 hours. Take the supernatant for later use.

[0073] (3) Add 0.1 parts by mass of cerium nitrate hexahydrate to 10 parts by mass of the supernatant obtained in step (2), and add 75 parts by mass of deionized water. Stir and react for 24 hours in a water bath at 25°C.

[0074] (4) Add 0.5 parts by mass of zinc nitrate hexahydrate to the solution obtained in step (3) and stir until completely dissolved;

[0075] (5) Add 0.3 parts by weight of benzotriazole and 1 part by weight of 2-methylimidazole to 25 parts by weight of anhydrous ethanol and stir until completely dissolved;

[0076] (6) Mix the solutions obtained in step (4) and step (5) and stir the mixture in a water bath at 25°C for 12 hours.

[0077] (7) The mixture obtained in step (6) is separated by a centrifuge. The precipitate is washed with deionized water by centrifugation and then dried in a 60°C oven to obtain BTA-ZIF-8@Ce-MMT nanocomposite powder.

[0078] Example 2

[0079] (1) Eight parts by weight of dried montmorillonite were ball-milled for 2 hours to obtain montmorillonite particles;

[0080] (2) Add 135 parts by mass of deionized water to the montmorillonite particles in step (1), disperse ultrasonically for 20 minutes, and allow to settle naturally for 24 hours. Take the supernatant for later use.

[0081] (3) Add 0.16 parts by mass of cerium nitrate hexahydrate to 14 parts by mass of the supernatant obtained in step (2), and add 87.5 parts by mass of deionized water. Stir and react for 24 hours in a water bath at 25°C.

[0082] (4) Add 0.95 parts by mass of zinc nitrate hexahydrate to the solution obtained in step (3) and stir until completely dissolved;

[0083] (5) Add 0.5 parts by weight of benzotriazole and 1.8 parts by weight of 2-methylimidazole to 32 parts by weight of anhydrous ethanol and stir until completely dissolved;

[0084] (6) Mix the solutions obtained in step (4) and step (5) and stir the mixture in a water bath at 25°C for 12 hours.

[0085] (7) The mixture obtained in step (6) is separated by a centrifuge. The precipitate is washed with deionized water by centrifugation and then dried in a 60°C oven to obtain BTA-ZIF-8@Ce-MMT nanocomposite powder.

[0086] Example 3

[0087] (1) 10 parts by weight of dried montmorillonite were ball-milled for 2 hours to obtain montmorillonite particles;

[0088] (2) Add 150 parts by mass of deionized water to the montmorillonite particles in step (1), disperse ultrasonically for 20 minutes, and allow to settle naturally for 24 hours. Take the supernatant for later use.

[0089] (3) Add 0.2 parts by mass of cerium nitrate hexahydrate to 20 parts by mass of the supernatant obtained in step (2), and add 90 parts by mass of deionized water. Stir and react for 24 hours in a water bath at 25°C.

[0090] (4) Add 1.5 parts by mass of zinc nitrate hexahydrate to the solution obtained in step (3) and stir until completely dissolved;

[0091] (5) Add 0.96 parts by weight of benzotriazole and 2.85 parts by weight of 2-methylimidazole to 40 parts by weight of anhydrous ethanol and stir until completely dissolved;

[0092] (6) Mix the solutions obtained in step (4) and step (5) and stir the mixture in a water bath at 25°C for 12 hours.

[0093] (7) The mixture obtained in step (6) is separated by a centrifuge. The precipitate is washed with deionized water by centrifugation and then dried in a 60°C oven to obtain BTA-ZIF-8@Ce-MMT nanocomposite powder.

[0094] 3. Performance Analysis of Examples and Comparative Experiments

[0095] Figure 1 The scanning electron microscope images show that the ball-milled montmorillonite exhibits a two-dimensional layered structure with cross-linked particles, indicating that MMT has high surface polarity.

[0096] Figure 2 This is a scanning electron microscope image of BTA-ZIF-8@Ce-MMT nanocomposite powder, showing an overall sheet-like structure with rhombic dodecahedral BTA-ZIF-8 nanoparticles on the surface, with a particle size of approximately 350–600 nm.

[0097] Figure 3 , 4This is the nitrogen adsorption curve and pore size distribution diagram of BTA-ZIF-8@Ce-MMT nanocomposite powder. As can be seen from the figure, the nanocomposite powder has a high specific surface area of ​​663 m². 2 / g, with an average pore size of around 0.4nm, the specific surface area of ​​MMT is significantly improved.

[0098] Figure 5 This is a release graph of BTA, the corrosion inhibitor in BTA-ZIF-8@Ce-MMT nanocomposite powder, at different time points. The release curves over time show that from pH=7 to pH=3, the release rate of the corrosion inhibitor gradually increases with increasing acidity, and the final release concentration also gradually increases. BTA release exhibits a strong acid-responsive release behavior.

[0099] Figure 6 This is a graph showing the release concentration of cerium ions, a corrosion inhibitor, from BTA-ZIF-8@Ce-MMT nanocomposite powder at different time points. Initially, cerium ions exhibit acid-responsive properties, but over time, the solution gradually penetrates the MMT interlayer, promoting the escape of cerium ions, ultimately resulting in a consistent cerium ion concentration at each pH level.

[0100] Comparative Experiment 1

[0101] 1. Using Q235 carbon steel blasted with 200-mesh glass sand as the substrate, waterborne epoxy protective coatings without corrosion inhibitors, waterborne epoxy protective coatings with 0.5% MMT, and waterborne epoxy protective coatings with 0.5% BTA-ZIF-8@Ce-MMT nanocomposite powder from Example 1 were sprayed onto the substrate, with a coating thickness of approximately 25 μm. After curing at 150°C for 1 hour, electrochemical impedance spectroscopy was collected for different immersion times in a 3.5% sodium chloride solution, as shown below. Figure 7 As shown.

[0102] 2. Compare the electrochemical impedance spectroscopy (EIS) of each sample surface after immersion in sodium chloride solution for different times. See details below. Figure 6 The comparative results show that the protective coating with added nanocomposite powder maintained a stable electrochemical impedance even after 28 days of immersion, while the protective coatings without and with added MMT both decreased by an order of magnitude. This is due to defects such as pores generated during the curing process of the waterborne epoxy coating and the incompatibility between MMT and the waterborne epoxy coating, respectively. Therefore, it can be seen that the nanocomposite powder of this invention can effectively improve the corrosion resistance of waterborne epoxy coatings over a long period.

[0103] Comparative Experiment 2

[0104] 1. Using Q235 carbon steel blasted with 200-mesh glass sand as the substrate, a water-based epoxy protective coating with no added MMT, 0.5% added MMT, and 0.5% added BTA-ZIF-8@Ce-MMT nanocomposite powder from Example 1 was sprayed onto the substrate to a thickness of approximately 25 μm. After curing at 150°C for 1 hour, an adhesion test was performed. Subsequently, after placing the substrate in a neutral salt spray chamber for two weeks, another adhesion test was conducted. Figure 7 As shown.

[0105] 2. Compare the adhesion of each coating before salt spray immersion; see details below. Figure 8 The adhesion strength of coatings with added nanocomposite powders was improved to some extent. After two weeks of soaking, the coating with 0.5% MMT showed the highest adhesion reduction rate, at 77%. The coating with 0.5% BTA-ZIF-8@Ce-MMT nanocomposite powder from Example 1 showed the lowest adhesion reduction rate, at 50.8%, while simultaneously exhibiting a 75% increase in adhesion compared to the blank coating. This demonstrates that the nanocomposite powders of this invention can significantly improve the dispersibility of MMT in waterborne epoxy coatings and enhance the protective performance of the coating.

Claims

1. A method for preparing BTA-ZIF-8@Ce-MMT nanocomposite powder supported by dual corrosion inhibitors, characterized in that, Includes the following steps: (1) Take dry montmorillonite, and ball mill it to obtain MMT particles; (2) Add an appropriate amount of deionized water to the MMT particles from step (1), disperse by ultrasonication, and allow to settle naturally; take the supernatant for later use. (3) Add cerium nitrate hexahydrate and an appropriate amount of deionized water to the supernatant of step (2) and react for 24 hours in a water bath at 25°C with stirring. (4) Add zinc nitrate hexahydrate to the reaction solution obtained in step (3) and stir until completely dissolved; (5) Add benzotriazole BTA and 2-methylimidazole to an appropriate amount of anhydrous ethanol and stir until completely dissolved; (6) Mix the two solutions obtained in step (4) and step (5), and then react them for 12 hours under water bath and stirring conditions at 25°C. (7) The reaction solution obtained in step (6) is centrifuged and separated. After centrifugation, washing and drying of the precipitate, BTA-ZIF-8@Ce-MMT nanocomposite powder is obtained. The mass ratio of montmorillonite (MMT), cerium nitrate hexahydrate, zinc nitrate hexahydrate, benzotriazole (BTA), and 2-methylimidazole used in the above steps is 6–10: 0.1–0.2: 0.5–1.5: 0.3–0.96: 1–2.

85.

2. The method according to claim 1, characterized in that, Based on 6-10 parts by weight of montmorillonite (MMT), 120-150 parts by weight of deionized water were added in step (2), and 10-20 parts by weight of the supernatant were taken; 75-90 parts by weight of deionized water were added in step (3); and 25-40 parts by weight of anhydrous ethanol were added in step (5).

3. The method according to claim 1, characterized in that, In step (1), the ball milling time is 2 hours, the frequency of the drive motor is 45Hz, and the rotation speed of the ball mill is 2700rpm.

4. The method according to claim 1, characterized in that, In step (2), the particles are ultrasonically dispersed for 20 minutes and allowed to settle naturally for 24 hours; the size of the MMT particles in the supernatant is ≤1μm.

5. The method according to claim 1, characterized in that, The purity of cerium nitrate hexahydrate, zinc nitrate hexahydrate, benzotriazole BTA, 2-methylimidazole, and anhydrous ethanol shall not be less than 99.7%.

6. The method according to claim 1, characterized in that, In steps (3) to (6), the stirring speed is 750 rpm.

7. The method according to claim 1, characterized in that, In step (7), the centrifugal separation speed is at least 5000 rpm and the time is at least 15 min; the centrifugal washing speed is at least 5000 rpm and the time is at least 15 min; the drying treatment is drying in a 60℃ oven.

8. A method for applying the dual corrosion inhibitor-supported BTA-ZIF-8@Ce-MMT nanocomposite powder prepared by the method according to any one of claims 1 to 7, characterized in that, The nanocomposite powder is added to the water-based epoxy resin anti-corrosion coating, with a mass ratio of 0.5% between the nanocomposite powder and the water-based epoxy resin anti-corrosion coating. After stirring evenly, the mixed coating is applied to the surface of the substrate by spraying or coating. The coating is then cured at 150°C for 1 hour to obtain a water-based epoxy resin anti-corrosion coating with active protection function.

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