Corrosion inhibitor-loaded bowl-shaped mesoporous polydopamine self-coated nanoparticles as well as preparation method and application thereof

Abstract

The invention relates to the field of self-repairing anticorrosive coatings, relates to a waterborne epoxy coating, and particularly relates to a corrosion inhibitor-loaded bowl-shaped mesoporous polydopamine self-coated nanoparticle as well as a preparation method and application thereof. According to the nanoparticles, bowl-shaped mesoporous polydopamine is taken as a base material, and the bowl-shaped mesoporous polydopamine self-coated nanoparticles loaded with the corrosion inhibitor are synthesized in situ by a one-step method by adopting an emulsion-induced interface anisotropy assembly method. The obtained nanoparticles can be used as an anticorrosive filler, and the corrosion inhibitor-loaded self-coated bowl-shaped mesoporous polydopamine nanoparticles provide a new thought for the design of a self-repairing anticorrosive coating with high loading capacity and quick response, and have potential application prospects in the aspect of prolonging the service life of a waterborne epoxy coating in an acid environment.

Description

Technical Field

[0001] The present invention relates to the field of self - healing anti - corrosion coatings, in particular to water - borne epoxy coatings, and specifically to bowl - shaped mesoporous polydopamine self - coated nanoparticles loaded with corrosion inhibitors, a preparation method thereof, and an application thereof. Background Art

[0002] At present, various strategies for controlling metal corrosion in acidic environments have been implemented. Among them, the method of covering a coating on the metal surface is the most effective, low - cost, and environmentally friendly method for preventing metal acidic corrosion. In particular, water - borne epoxy coatings have become a research hotspot and an important development direction in the coating field due to their extremely low amount of volatile compounds (VOCs), low emissions, energy conservation, and environmental friendliness. However, since the cured coating is exposed to a corrosive environment for a long time, it is very easy to form tiny damages and cracks, allowing corrosive media such as water, oxygen, and ions to penetrate into the cracks, promoting the corrosion reaction between the metal substrate and the media, resulting in material failure, and inevitably losing its barrier function easily. Exploring intelligent coatings with active self - healing functions is an effective strategy to eliminate this defect.

[0003] Corrosion inhibitors are the most widely studied self - healing additives for coatings. Usually, corrosion inhibitors are encapsulated in nano - containers before being incorporated into the coating. Storing them in nano - containers avoids the direct interaction between the corrosion inhibitor and the coating, avoiding many limitations. Such as nano - containers like mesoporous titanium dioxide, carbon nanotubes, zirconia, mesoporous silica, polydopamine, etc. Nano - containers have a wider range of structures and properties. While efficiently loading corrosion inhibitors, the nano - containers involved can respond to triggering factors in a timely manner, such as pH value, thermal responsiveness, and aqueous media. Only when these internal / external stimuli are triggered can the corrosion inhibitor be released from the nano - container. This can prevent the leakage of the corrosion inhibitor from the coating, achieve the controlled release of the corrosion inhibitor, increase the durability of the coating, thereby enhancing the self - healing ability of the coating and preventing corrosion. Among many triggering factors, the pH value is a key factor. Because corrosion may cause changes in the pH value at the corrosion site, and this process in turn affects the corrosion reaction. Therefore, the additional function of having a pH - controlled release effect is very important.

[0004] In these nanocontainers, the common problems are low loading capacity and slow responsiveness. The main obstacle is the design and preparation of ideal nanocontainers with high loading capacity and fast stimulus-responsive release. Recently, inspired by mussel adhesive proteins, dopamine has attracted increasing attention. Due to its chemical reactivity, biocompatibility, and low cytotoxicity, it has a wide range of applications in various fields such as drug delivery, catalysis, and energy. Dopamine has intrinsic pH responsiveness, and dopamine functional groups have great potential in increasing the adhesion of nanoparticles to planar surfaces. The relatively large mesopores and specific surface area in polydopamine can improve the loading capacity and rapid release of materials. A coating with PDA can be formed in an alkaline pH solution without any external stimuli such as light or heat, and its uniformity depends on PDA diffusion and surface reactivity. It is worth noting that the unreacted catechol groups after the oxidative polymerization of dopamine will leave abundant hydroxyl groups on the surface of the nanocontainers, making the modified nanocontainers have higher wettability. This property is crucial for nanocontainers dispersed in aqueous epoxy coatings. However, currently, mesoporous polydopamine nanospheres are a common method for obtaining pH-responsive nanocontainers. Due to the disadvantages of complex synthesis steps, low inhibitor loading capacity, and slow release responsiveness of these nanocontainers, there are still quite challenges in the design and preparation of self-healing anticorrosive coatings. Summary of the Invention

[0005] The object of the present invention is to provide a bowl-shaped mesoporous polydopamine self-coated nanoparticle loaded with an inhibitor, a preparation method thereof, and an application.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A preparation method of a bowl-shaped mesoporous polydopamine self-coated nanoparticle loaded with an inhibitor, using bowl-shaped mesoporous polydopamine as the base material, and adopting an emulsion-induced interfacial anisotropic assembly method to in-situ synthesize a bowl-shaped mesoporous polydopamine self-coated nanoparticle loaded with an inhibitor in one step.

[0008] Specifically

[0009] (1) Add triblock poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) and 1,3,5-trimethylbenzene to an ethanol-water mixed solution, stir at room temperature, then add dopamine, an inhibitor, and an ammonia aqueous solution, stir at room temperature, after centrifugation, wash the precipitate with an ethanol and water mixed solution by ultrasonic treatment, and centrifuge to obtain a bowl-shaped mesoporous polydopamine loaded with an inhibitor;

[0010] (2) Disperse the bowl-shaped mesoporous polydopamine loaded with an inhibitor obtained in step (1) in Tris buffer, add dopamine, stir at room temperature, after centrifugation, wash the precipitate with an ethanol and water mixed solution by ultrasonic treatment, and centrifuge to obtain a bowl-shaped mesoporous polydopamine nanoparticle loaded with an inhibitor and self-coated.

[0011] In step (1), 5 - 100 ml of water and 5 - 100 ml of ethanol are mixed evenly, 0.18 - 1.44 g of Pluronic F127 is added, then 500 - 3000 μL of m - xylene is dropped in, and stirred at room temperature for 5 - 300 min; 50 - 2000 mg of dopamine is added, then 75 - 3000 mg of corrosion inhibitor is added, and then 0.5 - 40 mL of ammonia water solution is dropped in, and stirred at room temperature for 0.5 - 2 h; after centrifugation, the precipitate is ultrasonically washed with a mixed solution of ethanol and water, and centrifuged to obtain bowl - shaped mesoporous polydopamine loaded with corrosion inhibitor.

[0012] In step (2), 25 - 75 mg of the bowl - shaped mesoporous polydopamine loaded with corrosion inhibitor obtained in step (1) is added to 5 - 100 ml of Tris - HCl buffer solution, stirred at room temperature for 0.5 - 1 h, then 50 - 100 mg of dopamine is added to the system and stirred for 2 - 48 h, washed and centrifuged to obtain bowl - shaped mesoporous polydopamine nanoparticles with self - coated corrosion inhibitor.

[0013] A kind of bowl - shaped mesoporous polydopamine self - coated nanoparticles loaded with corrosion inhibitor prepared by the said method, with large mesopores and large specific surface area prepared by the said method, to realize self - coated nanoparticles composed of bowl - shaped mesoporous polydopamine and dopamine shell with high loading capacity and fast acid - response rate for the loaded corrosion inhibitor.

[0014] An application of the said bowl - shaped mesoporous polydopamine self - coated nanoparticles loaded with corrosion inhibitor, the application of the bowl - shaped mesoporous polydopamine self - coated nanoparticles loaded with corrosion inhibitor as a filler for anti - corrosion coatings in acidic environments.

[0015] An aqueous epoxy coating, the aqueous epoxy coating contains the said bowl - shaped mesoporous polydopamine self - coated nanoparticles loaded with corrosion inhibitor.

[0016] The said bowl - shaped mesoporous polydopamine self - coated nanoparticles loaded with corrosion inhibitor are uniformly dispersed in the aqueous epoxy coating by the solution mixing method according to a content of 0.1 wt.% - 1 wt.%.

[0017] The said aqueous epoxy coating is composed of aqueous epoxy resin, curing agent and solvent.

[0018] The said nanoparticles are added to the aqueous epoxy coating, the preferred range is 0.05 wt.% - 2.5 wt.%, and the best range is 0.1 wt.% - 1 wt.%.

[0019] Furthermore, nanoparticles are added to the waterborne epoxy resin by a solution mixing method with magnetic stirring at room temperature, and an appropriate hardener must be used to cure the waterborne epoxy resin. The waterborne epoxy coating is a waterborne polymer, and water is used as a diluent for the resin and hardener in the waterborne coating. The solvent controls the coating viscosity, evaporation rate during the curing step, coating durability, and adhesion of the coating to the metal substrate.

[0020] An application of the waterborne epoxy coating as an anti-corrosion coating in an acidic environment.

[0021] Advantages of the present invention:

[0022] The present invention designs the structure of mesoporous polydopamine around a multifunctional emulsion-induced method, optimizes the synthesis process of mesoporous polydopamine, regulates the synthesis of bowl-shaped polydopamine nanocontainers with large mesopores and high specific surface area, and realizes a high loading amount of corrosion inhibitors. By simply loading heterocyclic organic corrosion inhibitors in one step, the loading amount of corrosion inhibitors is increased.

[0023] The present invention prepares for the first time polydopamine-coated bowl-shaped mesoporous polydopamine nanoparticles. Using them as carriers, the preparation method is simplified by a self-coating strategy, the composition is more single, and potential compatibility problems caused by complex systems are avoided. Covering a polydopamine layer on the surface can, on the one hand, prevent the loss of corrosion inhibitors in the nanocontainers in the coating, and at the same time endow the nanocontainers with an effective pH-triggering effect. The self-coated bowl-shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitors have a high loading amount of corrosion inhibitors, and have characteristics of fast response to pH changes, fast release rate of corrosion inhibitors, and high release amount in an acidic environment. Incorporated into the waterborne epoxy coating, multiple self-repairs can be achieved, and the anti-corrosion and self-repair functions of the waterborne epoxy coating can be improved. Brief Description of the Drawings

[0024] Figure 1 TEM images of bowl-shaped mesoporous polydopamine (a) and self-coated bowl-shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitors (b) provided by the embodiments of the present invention;

[0025] Figure 2 Thermogravimetric curves (a) and differential thermogravimetric curves (b) of self-coated bowl-shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitors provided by the embodiments of the present invention;

[0026] Figure 3 Release amounts of corrosion inhibitors of self-coated bowl-shaped mesoporous polydopamine nanoparticles within 24 hours at different pH values provided by the embodiments of the present invention;

[0027] Figure 4 Optical images after soaking in 3.5 wt.% NaCl solution at pH = 2 for 15 days provided by the embodiments of the present invention;

[0028] Figure 5 Bode plots of carbon steel electrodes coated with different coatings immersed in 3.5 wt.% NaCl solution with pH = 2 for different times: (a) pure waterborne epoxy coating, (b) waterborne epoxy nanocomposite coating containing 0.1 wt.% self-coated bowl-shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitor;

[0029] Figure 6 TEM image of spherical mesoporous polydopamine provided by the embodiment of the present invention;

[0030] Figure 7 Thermogravimetric curve (a) and differential thermogravimetric curve (b) of spherical mesoporous polydopamine nanoparticles loaded with corrosion inhibitor provided by the embodiment of the present invention. Detailed implementation manners

[0031] The manners are only for explaining and interpreting the present invention and are not limited to the present invention.

[0032] The present invention improves mesoporous polydopamine by using a multifunctional emulsion-induced method, optimizes the synthesis reaction time process of mesoporous polydopamine, regulates the synthesis of bowl-shaped polydopamine nanocontainers with large mesopores and large specific surface areas of specific structures, and realizes a high loading amount of corrosion inhibitor. By simply loading heterocyclic organic corrosion inhibitors in one step, the loading amount of the corrosion inhibitor is increased. Self-coated nanoparticles composed of bowl-shaped mesoporous polydopamine and dopamine shells are constructed. Covering the surface with a dopamine layer not only prevents the loss of the corrosion inhibitor in the nanocontainer in the coating, but also enables the nanocontainer to have an effective pH-triggering effect. Incorporating the above-mentioned self-coated bowl-shaped mesoporous polydopamine particles loaded with corrosion inhibitor as anti-corrosion coating fillers into waterborne coatings, thereby realizing multiple self-repairs and improving the anti-corrosion and self-repair performances of waterborne coatings. Its excellent anti-corrosion and self-repair performances have broad application prospects in acidic corrosion environments.

[0033] The polydopamine-based nanomaterials of the present invention for waterborne organic coatings (i.e., self-coated bowl-shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitor) are used to improve the anti-corrosion and self-repair performances of waterborne epoxy coatings on metal substrates.

[0034] Example 1

[0035] Preparation method of self-coated bowl-shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitor, comprising the following steps:

[0036] (1) Mix 5 ml of water and 5 ml of ethanol, add 0.18 g of Pluronic F127, then drop in 500 μL of m - xylene, and stir at room temperature for 5 min; add 50 mg of dopamine, then add 75 mg of 2 - mercaptobenzimidazole (2 - MBI), and then drop in 0.5 mL of ammonia water solution, and stir at room temperature for 0.5 h; after centrifugation, wash the precipitate ultrasonically three times with a mixed solution of ethanol and water, and centrifuge at 10000 r for 15 min to obtain bowl - shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitor.

[0037] (2) Take 5 mg of the bowl - shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitor obtained in step (1), disperse them in 5 ml of Tri - HC1 buffer solution, stir and react at room temperature, add 5 mg of dopamine and continue to stir for 2 h, wash and centrifuge at 10000 r for 10 min to obtain bowl - shaped mesoporous polydopamine nanoparticles with self - coated corrosion inhibitor (see Figure 1 and 2 ).

[0038] Use a transmission electron microscope to record the morphologies of the bowl - shaped mesoporous polydopamine and the bowl - shaped mesoporous polydopamine nanoparticles with self - coated corrosion inhibitor. As shown in Figure 1 a, the nanoparticles have large mesopores with radial - oriented order, and the mesopores are arranged radially from the center to the surface. These mesopores are uniformly distributed in the bowl - shaped mesoporous polydopamine nanoparticles, forming a hollow multi - tube structure with cylindrical open channels. As shown in Figure 1 b, due to the encapsulation of polydopamine, an organic coating layer can also be observed at the edge of the bowl - shaped mesoporous polydopamine.

[0039] Perform thermogravimetric analysis on the bowl - shaped mesoporous polydopamine nanoparticles with self - coated corrosion inhibitor to test the loading efficiency of the prepared nanocontainer. As shown in Figure 2 , the loading content of the bowl - shaped mesoporous polydopamine nanoparticles with self - coated corrosion inhibitor is about 24.08%, showing good corrosion inhibitor loading efficiency.

[0040] Example 2

[0041] In order to evaluate the process of corrosion inhibitor release from the container, the release behavior of the bowl - shaped mesoporous polydopamine nanoparticles with self - coated corrosion inhibitor at different pH values was tested by UV - Vis. Taking the absorbance intensity of the released 2 - mercaptobenzimidazole as a function of time, monitor the release performance of the corrosion inhibitor in the bowl - shaped mesoporous polydopamine nanoparticles sample with self - coated corrosion inhibitor at different pH values (see Figure 3 ).

[0042] As shown in Figure 3When the external environmental pH is 7, 4, and 2 respectively, the release rates of 2-mercaptobenzimidazole after 24 h are 24.83%, 47.62%, and 91.61% respectively. The release rate of 2-mercaptobenzimidazole is relatively small under neutral conditions, and about 75% of the 2-mercaptobenzimidazole molecules remain in the nanoparticles. The release rate at pH = 4 is between the release rates at pH = 7 and pH = 2. When the external environmental pH = 2, the release rate of 2-mercaptobenzimidazole significantly accelerates within 0 - 24 h, and the release trend becomes significantly larger. More than 90% of the 2-mercaptobenzimidazole is released from the nano-container at 12 h.

[0043] Example 3

[0044] The self-coated bowl-shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitors obtained in Example 1 above are used as anti-corrosion nano-fillers in waterborne epoxy coatings and are applied by brushing the coating on a clean steel substrate.

[0045] A waterborne epoxy composite coating containing 0.1 wt.% of self-coated bowl-shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitors is prepared by a solution mixing method:

[0046] First, 70 mg of the self-coated bowl-shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitors obtained above are added to deionized water for dispersion, and then added to 70 g of waterborne epoxy resin for strong magnetic stirring and probe sonication. Subsequently, 35 g of curing agent is added and stirred continuously. After dilution with deionized water and standing to remove bubbles, the waterborne epoxy composite coating is obtained. The waterborne epoxy resin (MU-618) and the curing agent (CU-600) are both purchased from Shanghai Run Carbon New Materials Technology Co., Ltd.

[0047] Then, the waterborne epoxy composite coating prepared above is coated on a Q235 carbon steel plate, and the coating thickness is about 60 ± 5 μm. After curing at room temperature, it is cured in an 80 °C oven for 90 min. At the same time, a pure waterborne epoxy coating is used as a control, and the pure waterborne epoxy coating is a blank waterborne epoxy coating without adding self-coated bowl-shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitors.

[0048] The corrosion resistance of the pure waterborne epoxy coating and the nano-composite waterborne epoxy coating is evaluated by immersion tests and electrochemical impedance, as Figure 4 and Figure 5 shown.

[0049] Specifically:

[0050] 1) The immersion test is as follows: The scratched coating samples are directly immersed in a 3.5 wt.% NaCl solution with pH = 2 to study the anti-corrosion and self-healing properties of the prepared coatings. From Figure 4Image observation of the coated samples after 15 days of immersion. Corrosion products, blisters, and coating failure occurred in the pure waterborne epoxy coating, while the nanocomposite coating remained defect-free, and only small corrosion spots could be seen on the scratches, with the corrosion degree significantly lighter than that of the pure waterborne epoxy coating.

[0051] 2) Electrochemical impedance was used to evaluate the corrosion resistance and self-healing properties of the pure waterborne epoxy coating and the nanocomposite waterborne epoxy coating.

[0052] The corrosion resistance of the nanocomposite waterborne epoxy coating was evaluated by an electrochemical workstation Autolab PGSTAT302N. A three-electrode system was adopted, including an auxiliary electrode (4 cm 2 platinum sheet), a working electrode (coated electrode), and a reference electrode (saturated calomel electrode, SCE), and the test was carried out in a 3.5 wt.% sodium chloride solution with pH = 2. Before the experiment, the open-circuit potential of the specimen was measured in the corrosion medium, and the change in the open-circuit potential was recorded. The electrochemical impedance spectroscopy was carried out when the open-circuit potential was stable. The frequency range of the electrochemical impedance spectroscopy test was set to 10 5 Hz to 0.01 Hz, and the amplitude of the alternating current sine perturbation signal was set to 5 Mv (see Figure 5 ).

[0053] For the blank waterborne epoxy coating, the impedance modulus |Z| at a frequency of 0.01 Hz decreased from 1.06×10 4 Ω·cm 2 at the beginning to 8.27×10 3 Ω·cm 2 after 20 days of immersion, indicating the corrosion of the carbon steel substrate and the rapid failure of the blank waterborne epoxy coating. However, the impedance value of the nanocomposite waterborne epoxy coating showed a recovery phenomenon on the 3rd day, and the impedance modulus |Z| value at a frequency of 0.01 Hz after 20 days of immersion was 1.84×10 6 Ω·cm 2 , which was 3 orders of magnitude higher than that of the blank waterborne epoxy coating. In a 3.5 wt.% acidic sodium chloride solution with pH = 2, the nanocomposite waterborne epoxy coating efficiently and controllably released 2-mercaptobenzimidazole inhibitor on the surface of carbon steel, and the formed repair film played a shielding role in the corrosion reaction. The higher impedance value was mainly due to the enhanced compatibility of dopamine adhesion with waterborne epoxy resin and the synergistic corrosion inhibition effect of 2-mercaptobenzimidazole and dopamine, showing good anti-corrosion and self-healing properties. Due to the intelligent repair characteristics of this coating in acidic media, it has potential application value in the field of corrosion protection.

[0054] Comparative Example 1

[0055] 1) Preparation method of spherical mesoporous polydopamine nanoparticles loaded with corrosion inhibitor, including the following steps:

[0056] (1) Mix 5 mL of water and 5 mL of ethanol, add 0.18 g of Pluronic F127, then dropwise add 500 μL of m - xylene, and stir at room temperature for 10 min; add 50 mg of dopamine, then add 2 - mercaptobenzimidazole (2 - MBI), and then dropwise add 0.5 mL of ammonia water solution, and stir at room temperature for 24 h; after centrifugation, wash the precipitate ultrasonically three times with a mixed solution of ethanol and water, and centrifuge to obtain spherical mesoporous polydopamine nanoparticles loaded with corrosion inhibitors (see Figure 6 and 7 ).

[0057] Use a transmission electron microscope to record the morphology of the spherical mesoporous polydopamine nanoparticles. As Figure 6 shown, spherical mesoporous polydopamine particles with ordered mesopores are formed.

[0058] Perform thermogravimetric analysis on the spherical mesoporous polydopamine nanoparticles loaded with corrosion inhibitors to test the loading efficiency of the prepared nanocontainers. As Figure 7 shown, the loading content of the spherical mesoporous polydopamine nanoparticles loaded with corrosion inhibitors is about 14.73%. The loading capacity of the bowl - shaped mesoporous polydopamine is nearly 10% higher than that of the spherical mesoporous polydopamine. The large mesoporous structure and large specific surface area of the bowl - shaped mesoporous polydopamine improve the loading capacity of the corrosion inhibitor, which confirms that the bowl - shaped mesoporous polydopamine can provide an ideal reservoir for the corrosion inhibitor.

[0059] Example 4

[0060] 1) Preparation method of bowl - shaped mesoporous polydopamine self - coated nanoparticles loaded with corrosion inhibitors, including the following steps:

[0061] (1) Mix 50 mL of water and 50 mL of ethanol, add 1 g of Pluronic F127, then dropwise add 2 mL of m - xylene, and stir at room temperature for 5 min; add 1.5 g of dopamine, then add 1.8 g of 2 - mercaptobenzimidazole (2 - MBI), and then dropwise add 3.75 mL of ammonia water solution, and stir at room temperature for 2 h; after centrifugation, wash the precipitate ultrasonically three times with a mixed solution of ethanol and water, and centrifuge to obtain bowl - shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitors.

[0062] (2) Take 50 mg of the mesoporous polydopamine nanoparticles obtained in step (1), disperse them in 100 mL of Tri - HCl buffer solution, stir and react at room temperature, add 50 mg of dopamine and continue to stir for 12 h, wash and centrifuge to obtain bowl - shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitors and self - coated.

[0063] 2) The bowl - shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitors and self - coated are used as anti - corrosion nano - fillers in water - borne epoxy coatings and are applied by brushing the coating on a clean steel substrate.

[0064] Preparation of a composite waterborne epoxy coating containing 0.1 wt.% of inhibitor-loaded self-coated bowl-shaped mesoporous polydopamine nanoparticles by solution mixing method: First, disperse 70 mg of the inhibitor-loaded self-coated bowl-shaped mesoporous polydopamine nanoparticles obtained above in deionized water, and then add it to 70 g of waterborne epoxy resin for strong magnetic stirring and probe sonication. Subsequently, add 35 g of hardener and stir continuously. After dilution with deionized water, let it stand to remove bubbles to obtain the composite waterborne epoxy coating. The waterborne epoxy resin (MU-618) and the curing agent (CU-600) are both purchased from Shanghai Run Carbon New Materials Technology Co., Ltd. Brush the obtained coating on a steel substrate, cure it at room temperature, and then cure it in an oven at 80 °C for 90 min.

[0065] Example 5

[0066] 1) Preparation method of inhibitor-loaded bowl-shaped mesoporous polydopamine self-coated nanoparticles, including the following steps:

[0067] (1) Mix 5 ml of water and 5 ml of ethanol, add 0.1 g of Pluronic F127, then drop in 0.2 ml of mesitylene, and stir at room temperature for 5 min; add 0.15 g of dopamine, then add 0.2 g of 2-mercaptobenzimidazole (2-MBI), and then drop in 0.375 mL of ammonia water solution, and stir at room temperature for 2 h; after centrifugation, wash the precipitate three times by ultrasonic treatment with a mixed solution of ethanol and water, and centrifuge to obtain inhibitor-loaded bowl-shaped mesoporous polydopamine nanoparticles.

[0068] (2) Take 150 mg of the mesoporous polydopamine nanoparticles obtained in step (1), disperse them in 100 ml of Tri-HCl buffer solution, stir and react at room temperature, add 50 mg of dopamine and continue to stir for 24 h, wash and centrifuge to obtain inhibitor-loaded self-coated bowl-shaped mesoporous polydopamine nanoparticles.

[0069] 2) The inhibitor-loaded self-coated bowl-shaped mesoporous polydopamine nanoparticles are used as anti-corrosion nano-fillers in the waterborne epoxy coating and are applied by brushing the coating on a clean steel substrate.

[0070] Preparation of a composite waterborne epoxy coating containing 0.1 wt.% of inhibitor-loaded self-coated bowl-shaped mesoporous polydopamine nanoparticles by solution mixing method: First, disperse 70 mg of the inhibitor-loaded self-coated bowl-shaped mesoporous polydopamine nanoparticles obtained above in deionized water, and then add it to 70 g of waterborne epoxy resin for strong magnetic stirring and probe sonication. Subsequently, add 35 g of hardener and stir continuously. After dilution with deionized water, let it stand to remove bubbles to obtain the composite waterborne epoxy coating. The waterborne epoxy resin (MU-618) and the curing agent (CU-600) are both purchased from Shanghai Run Carbon New Materials Technology Co., Ltd.

[0071] Apply the obtained coating on the steel substrate. After curing at room temperature, cure it in an oven at 80 °C for 90 min.

[0072] In summary, as an anticorrosive filler, the nanoparticles of the present invention can improve the anticorrosion and self-healing properties of the waterborne coating after being added to the waterborne coating and forming a waterborne coating on the substrate. Thermogravimetric experiments prove that the nano-filler has a large loading capacity of the corrosion inhibitor. The corrosion inhibitor release experiment shows that the polydopamine shell has pH sensitivity and gating effect, and has a high release amount in an acidic environment. Electrochemical experiments prove that the nanoparticles have good anticorrosion and self-healing effects. The self-coated bowl-shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitor provide a new idea for the design of self-healing anticorrosive coatings with high loading capacity and rapid response, and have potential application prospects in improving the service life of waterborne epoxy coatings in acidic environments.

Claims

1. A method for preparing bowl-shaped mesoporous polydopamine self-coated nanoparticles loaded with corrosion inhibitor, characterized in that: Bowl-shaped mesoporous polydopamine was used as the basic material and the emulsion-induced interfacial anisotropic assembly method was adopted to synthesize bowl-shaped mesoporous polydopamine self-coated nanoparticles loaded with corrosion inhibitor in situ in one step.

2. The method for preparing bowl-shaped mesoporous polydopamine self-coated nanoparticles loaded with corrosion inhibitor according to claim 1, characterized in that: (1) adding triblock polyethylene oxide-b-polypropylene oxide-b-polyethylene oxide and 1,3,5-trimethylbenzene to an ethanol-water mixed solution, stirring at room temperature, then adding dopamine, a corrosion inhibitor and an ammonia solution, stirring at room temperature, centrifuging, ultrasonically washing the precipitate with an ethanol-water mixed solution, and centrifuging to obtain a bowl-shaped mesoporous polydopamine loaded with a corrosion inhibitor; (2) The bowl-shaped mesoporous polydopamine loaded with corrosion inhibitor obtained in step (1) is dispersed in Tris buffer, dopamine is added, stirred at room temperature, and the precipitate is ultrasonically washed with a mixed solution of ethanol and water after centrifugation, and the bowl-shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitor are obtained by centrifugation.

3. The method for preparing bowl-shaped mesoporous polydopamine self-coated nanoparticles loaded with corrosion inhibitor according to claim 2, characterized in that: In the step (1), 5-100 ml of water and 5-100 ml of ethanol are mixed, 0.18-1.44 g of Pluronic F127 is added, and then 500-3000 μL of m-trimethylbenzene is dropped, and the mixture is stirred at room temperature for 5-300 min; 50-2000 mg of dopamine is added, and then 75-3000 mg of a corrosion inhibitor is added, and then 0.5-40 mL of an ammonia solution is dropped, and the mixture is stirred at room temperature for 0.5-2 h; after centrifugation, the precipitate is ultrasonically washed with a mixed solution of ethanol and water, and centrifuged to obtain a bowl-shaped mesoporous polydopamine loaded with a corrosion inhibitor.

4. The method for preparing bowl-shaped mesoporous polydopamine self-coated nanoparticles loaded with corrosion inhibitor according to claim 2, characterized in that: In the step (2), 25 to 75 mg of the bowl-shaped mesoporous polydopamine loaded with corrosion inhibitor obtained in step (1) is added to 5 to 100 ml of Tris-HCl buffer, and the reaction is stirred at room temperature for 0.5 to 1 hour, and then 50 to 100 mg of dopamine is added to the system and stirring is continued for 2 to 48 hours, followed by washing and centrifugation to obtain bowl-shaped mesoporous polydopamine nanoparticles loaded with corrosion inhibitor.

5. Bowl-shaped mesoporous polydopamine self-coated nanoparticles loaded with corrosion inhibitor prepared by the method of claim 1, characterized in that: The method of claim 1 is used to prepare self-coated nanoparticles composed of bowl-shaped mesoporous polydopamine and a dopamine shell layer, which have large mesopores and a large specific surface area and are loaded with corrosion inhibitors with high loading amount and fast acid response rate.

6. An application of the bowl-shaped mesoporous polydopamine self-coated nanoparticles loaded with corrosion inhibitor according to claim 5, characterized in that: The bowl-shaped mesoporous polydopamine self-coated nanoparticles loaded with corrosion inhibitor are used as anti-corrosion coating fillers.

7. A waterborne epoxy coating, characterized in that: The waterborne epoxy coating contains the bowl-shaped mesoporous polydopamine self-coated nanoparticles loaded with corrosion inhibitor according to claim 1.

8. The waterborne epoxy coating according to claim 1, characterized in that: The bowl-shaped mesoporous polydopamine self-coated nanoparticles loaded with corrosion inhibitor according to claim 1 are uniformly dispersed in a waterborne epoxy coating at a content of 0.1 wt.% to 1 wt.% by a solution mixing method.

9. An application of the waterborne epoxy coating according to claim 7, characterized in that: The water-based epoxy coating is used as an anti-corrosion coating in an acidic environment.

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