Acid-base responsive boron nitride nanoreservoir driven self-healing and anti-aging synergistic anticorrosion coating and preparation method thereof

Abstract

This invention discloses an acid-base responsive boron nitride nanocontainer-driven self-healing and aging-resistant synergistic anti-corrosion coating and its preparation method. The method involves in-situ growth of polydopamine on a hydroxylated boron nitride nanosheet carrier, followed by loading a benzotriazole corrosion inhibitor to obtain an acid-base responsive, highly loaded active nanocontainer (BPB). This BPB is then embedded in an epoxy resin matrix to obtain a composite anti-corrosion coating, EP-BPB. This invention's acid-base responsive, controllable-release BPB nanocontainer-assisted self-healing epoxy composite coating enables the coating to exhibit a rapid response to substrate corrosion. The released corrosion inhibitor migrates to the corroded substrate and forms a reliable protective molecular film, thereby maximizing the coating's anti-corrosion performance. Simultaneously, the coating of this invention possesses excellent UV resistance, maintaining stability under long-term exposure, making it suitable for in-situ corrosion protection of marine equipment.

Description

Technical Field

[0001] This invention belongs to the field of anti-corrosion coatings for nanomaterials, and relates to an acid-base responsive boron nitride nanocontainer-driven self-healing and aging-resistant synergistic anti-corrosion coating and its preparation method. Background Technology

[0002] Coatings can serve as simple protective shields, preventing corrosive media from directly contacting metal surfaces. Organic coatings such as epoxy (EP) and polyurethane (PU) resins offer advantages such as ease of application and cost-effectiveness. Among them, epoxy resins are more widely used due to their excellent mechanical properties, electrical resistance, chemical inertness, and adhesion to substrates. However, due to the harsh corrosive environment of the ocean, traditional EP organic anti-corrosion coatings are prone to damage and premature failure under complex environmental conditions, making it difficult to provide sustained corrosion protection for metal materials. Therefore, developing environmentally adaptable intelligent anti-corrosion coatings to improve the durability of traditional anti-corrosion coatings and overcome the corrosion damage problems of marine facilities has a significant impact on the development of the marine industry.

[0003] By cleverly designing optimized structures incorporating functional molecules and combining them with the evolution of intelligent thin films possessing self-healing capabilities, localized corrosion at the metal-coating interface can be rapidly controlled. Therefore, this method not only protects the metal substrate but also provides basic corrosion protection, potentially overcoming the limitations of existing technologies and offering more effective protection. To date, highly environmentally adaptable externally assisted adaptive self-healing protective coatings can be categorized based on their active self-healing mode into microcapsule / microcontainer technology and intelligent micro / nanocontainer self-healing anti-corrosion coating materials.

[0004] Unlike the first-generation "microcapsule / microvascular healer" external self-healing coating, the external smart self-healing coating of the nanocontainer with added corrosion inhibitors is stimulated by pH fluctuations in the nanocontainer when the metal substrate corrodes, causing changes in the environmental pH and triggering the release of the corrosion inhibitor. More importantly, even with a very low concentration of the loaded corrosion inhibitor, the redox activity of the metal surface is greatly reduced, thus preventing metal degradation.

[0005] While traditional particles and nanoparticles can provide self-healing capabilities for corrosion inhibitor storage and release in coatings, they are not conducive to improving the barrier properties of the coatings. Furthermore, they tend to create unwanted micropores in the coating, thus limiting their use in corrosion protection applications. In contrast, two-dimensional materials, such as various organic / inorganic nanosheets, are of great significance in the field of materials science and technology due to their unique high specific surface area and ultrathin structure. Two-dimensional nanosheets can act as physical barriers to prevent corrosive media (such as H₂O, Cl₂, etc.) from entering the coating. - (and O2) penetrate into the coating substrate, thereby significantly improving the corrosion resistance of traditional polymer substrates.

[0006] Hexagonal boron nitride (H-BN), often referred to as "white graphene," possesses graphene-like properties, including excellent impermeability, mechanical strength, and thermal conductivity. Due to the high electronegativity of nitrogen, H-BN exhibits a significant band gap as an electrical insulator, making it a popular two-dimensional nanomaterial for corrosion protection. Unlike the AB stacking of graphene, the AA stacking of H-BN results in stronger interlayer polar interactions compared to the van der Waals forces in graphene, making H-BN exfoliation more complex. Therefore, untreated bulk H-BN is less effective in enhancing the corrosion protection of coatings, as its surface lacks functional groups and cannot be uniformly dispersed in the resin matrix (Xu Fei, Ye Peng, Peng Jianwen, et al., Cerium Methacrylate Assisted Preparation of Highly Thermally Conductive and Anticorrosive Multifunctional Coatings for Heat Conduction Metals Protection, Nano-MicroLetters, 2023, 15, 201.).

[0007] Polydopamine (PDA) is a polymer with a unique structure that can self-polymerize via dopamine (DA) in a weakly alkaline environment, and its surface is rich in active functional groups. This structure endows PDA with excellent biocompatibility, adhesion, and near-infrared light response properties, making it suitable for use in intelligent self-healing anti-corrosion coatings. Most importantly, its abundant amine functional groups and the adhesive properties of catechols enable PDA to effectively bind with a variety of materials, making it an ideal carrier for corrosion inhibitors. Furthermore, the interaction of PDA with metals and metal oxides gives it the ability to act as a green corrosion inhibitor, effectively protecting the substrate. The chelating effect of natural melanin on metal ions can be achieved by forming catechol-Fe on steel. 3+ or catechol-Fe 2 + The complex further reduces the risk of corrosion.

[0008] Benzotriazole (BTA), a low-toxicity organic corrosion inhibitor with a small molecular weight, has been widely used as a corrosion inhibitor for copper and steel. Selecting appropriate corrosion inhibitors and their dosage can effectively promote the self-healing and corrosion resistance of coatings. Liu Chengbao et al. synthesized a novel supramolecular nanocontainer based on graphene / β-cyclodextrin, which exhibits excellent inhibitor encapsulation ability and high impermeability. The BTA-loaded nanocontainer was then used to impart excellent passive and active corrosion protection to the coating system. However, the aforementioned anti-corrosion coatings suffer from problems such as low inhibitor loading or inability to achieve long-term sustained release (Liu Chengbao, Zhao Haichao, Hou Peimin, et al, Efficient Graphene / Cyclodextrin-Based Nanocontainer: Synthesis and Host-Guest Inclusion for Self-Healing Anticorrosion Application, ACS Appl. Mater. Interfaces 2018, 10, 36229-36239). Therefore, the challenges of corrosion inhibitor loading and long-term controllable release for nano-container-enhanced anti-corrosion coatings remain unsolved. Summary of the Invention

[0009] The present invention aims to provide an acid-base responsive boron nitride nanocontainer-driven self-healing and anti-aging synergistic anti-corrosion coating and its preparation method. The method involves the self-polymerization of dopamine and the loading of benzotriazole on a hydroxylated boron nitride nanosheet (BNNS) framework to prepare a smart nanocontainer BNNS / PDA / BTA, which is then composited with epoxy resin to obtain a self-healing and anti-aging synergistic anti-corrosion coating.

[0010] The technical solution for achieving the objective of this invention is as follows:

[0011] A method for preparing an acid-base responsive boron nitride nanocontainer-driven self-healing and aging-resistant synergistic anti-corrosion coating includes the following steps:

[0012] (1) Self-polymerization of sensitive layer PDA on BNNS nanosheets: Tris(hydroxymethyl)aminomethane hydrochloride (TrB-HCl) was added to a suspension of hydroxylated boron nitride nanosheets, the pH was adjusted to 8.0-8.5, and dopamine was added. The reaction was stirred in the dark, and after the reaction was completed, the nanosheets were centrifuged and washed to obtain BNNS / PDA nanomaterials (BP).

[0013] (2) Adsorption of corrosion inhibitor BTA: BNNS / PDA nanosheets were added to a saturated benzotriazole ethanol solution and the adsorption reaction was carried out under vacuum. After the reaction was complete, the nanosheets were washed with water and centrifuged to obtain the intelligent nanocontainer BNNS / PDA / BTA (BPB).

[0014] (3) Preparation of BPB-enhanced epoxy resin coating: The smart nanocontainer BNNS / PDA / BTA was ultrasonically dispersed in ethanol. Then, the ethanol dispersion of the smart nanocontainer BNNS / PDA / BTA was mixed with the epoxy resin at a mass of 0.5±0.1% of the mass of the epoxy resin. The mixture was stirred until homogeneous, and then the excess solvent was removed by rotary evaporation. A curing agent was added to the mixture, and the reaction was continued to densify the coating. After degassing, the EP-BPB coating was obtained.

[0015] Further, in step (1), the preparation method of hydroxylated boron nitride nanosheets is as follows: hexagonal boron nitride nanosheets are exfoliated and surface hydroxylated by liquid phase ultrasonic exfoliation. Hexagonal boron nitride nanosheets, ethylene glycol and N,N-dimethylformamide (DMF) are mixed and ultrasonically exfoliated. Then, the supernatant is collected by centrifugation, centrifugation is performed again, the precipitate is collected, the precipitate is washed with water and filtered, and dried to obtain hydroxylated boron nitride nanosheets.

[0016] Furthermore, in step (1), the mass ratio of hydroxylated boron nitride nanosheets to dopamine is 0.4 to 0.9:1.

[0017] Furthermore, in step (1), the centrifugation speed is 8000-10000 rpm and the centrifugation time is 10-15 min.

[0018] Furthermore, in step (2), the concentration of benzotriazole in the ethanol solution of benzotriazole is 80 mg / mL.

[0019] Furthermore, in step (2), the adsorption reaction time is more than 12 hours.

[0020] Furthermore, in step (3), the concentration of the intelligent nanocontainer BNNS / PDA / BTA in the ethanol dispersion is 20 mg / mL.

[0021] The present invention provides a coating obtained by the above preparation method.

[0022] The present invention also provides the application of the above coating in metal corrosion protection.

[0023] Furthermore, the metals include, but are not limited to, Q235 carbon steel, magnesium alloys, aluminum alloys, brass, etc.

[0024] This invention utilizes a liquid-phase ultrasonic exfoliation method to prepare hydroxylated boron nitride nanosheets, which exhibit a monolayer or few-layer dispersion structure. This structure inhibits large-scale aggregation and improves interfacial compatibility with the coating substrate, thereby maximizing the corrosion resistance of the coating. Furthermore, by leveraging the π-π stacking and van der Waals interactions between the conjugated hydroxylated boron nitride nanosheets and the dopamine benzene ring, as well as the nucleophilic reaction and molecular rearrangement ability of dopamine under weakly alkaline conditions, the self-polymerization of dopamine on the surface of the hydroxylated boron nitride nanosheets is promoted, thus forming BNNS / PDA nanomaterials. Using polydopamine as a sensitive layer, benzotriazole is adsorbed onto the BNNS / PDA nanomaterials through π-π stacking and interfacial hydrogen bonding interactions, resulting in BNNS / PDA / BTA nanomaterials. Since both benzotriazole and polydopamine are amphoteric compounds, they can exist in neutral, anionic, and cationic forms depending on the solution pH. In strongly acidic solutions (pH < 4.11), it exists in the protonated form BTAH. 2+ It exists. In weakly acidic / basic / weakly acidic solutions, it exists as benzotriazole. In strongly alkaline solutions (pH>4.11), it exists as BTA. -Polydopamine exists in the form of [missing information - likely a specific chemical compound]. The Isp of polydopamine is typically pH = 4.0 ± 0.5. Due to amine protonation, polydopamine carries a positive charge in solutions with pH < 4.0. However, in solutions with pH > 4.0, polydopamine carries a negative charge due to the deprotonation of the phenolic group. Therefore, the charge state of the polydopamine film affects the uptake and release characteristics of charged molecules. In neutral solutions, polydopamine attaches functional ligands to the surface of hydroxylated boron nitride nanosheets through physical interactions (hydrogen bonds, π-π stacking) or chemical bonds (Michael addition or Schiff base reaction). More importantly, a physical bond (hydrogen bond, π-π stacking) exists between polydopamine and benzotriazole. The electrostatic repulsion between them leads to a significant enhancement in the release behavior of benzotriazole at acidic / alkaline pH conditions. Furthermore, polydopamine is unstable in acidic environments. This may be related to the ring-closing step during polymerization and the increased -NH2 content, which also contributes to the release of benzotriazole. Hydroxylated boron nitride nanosheets, benzotriazole, and polydopamine exhibit particularly strong UV absorption and scattering capabilities, absorbing UV wavelengths from 280 to 400 nm. They can form a shielding film on the material surface, absorbing or reflecting UV rays, reducing direct UV exposure to the polymer matrix, and thus preventing material degradation. The high specific surface area of ​​BNNS / PDA / BTA nanomaterials allows for more physical and chemical interactions with epoxy resin polymer chains, which helps improve resistance to UV aging. Therefore, adding an appropriate amount of BNNS / PDA / BTA nanomaterials to epoxy coatings can reflect some ambient UV radiation, reducing UV absorption by the epoxy resin and preventing the breakage of OH, -RCONH, and CO bonds in the epoxy resin.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) The acid / base dual-stimulation responsive nanocontainer BPB of the present invention uses BNNS as a carrier. The average aspect ratio of BNNS is 589.58%, and it has water dispersion stability. In addition, by utilizing the π-π stacking and van der Waals interaction between the conjugated BNNS and the dopamine benzene ring, as well as the nucleophilic reaction and molecular rearrangement ability of dopamine under weakly alkaline conditions, the self-polymerization of dopamine on the surface of BNNS is promoted, thereby forming BNNS / PDA nanomaterials. On the other hand, PDA is used as a sensitive layer. BTA is adsorbed on the BNNS / PDA nanomaterials through the π-π stacking and interfacial hydrogen bonding interaction between the BNNS / PDA nanomaterials and BTA. The BTA content of the corrosion inhibitor loaded in the formed nanocontainer BPB is as high as 168.4 μg / mg.

[0027] (2) The acid / base dual-stimulation responsive nanocontainer of the present invention demonstrated through BPB-stimulated release experiments that its release rate under different acid / base environments (pH 2 / 11) was higher than that under neutral environment (pH 7). At a release time of 780 min, the total release at pH 2 was 32.40%, higher than at pH 11 (25.28%) and pH 7 (22.15%). The electrostatic repulsion between the two environments significantly enhanced the release behavior of BTA under acidic / alkaline pH conditions. Furthermore, PDA is unstable in acidic environments. This may be related to the ring-closing step in the polymerization process and the increased -NH2 content. This also contributes to the release of BTA. Therefore, by utilizing the changes in amino and hydroxyl charges with pH, ​​the release behavior of the PDA sensitive layer system can be customized according to a specific pH value.

[0028] (3) The acid / base dual-stimulation responsive nanocontainer BPB of the present invention can achieve a corrosion inhibition efficiency of 58.38% even in a low concentration (20.0 mg / L) 3.5 wt% NaCl environment. Under different acid and base conditions of 200.0 mg / L 3.5 wt% NaCl, the water contact angle of the bare Q235 carbon steel surface indicates that the released BTA and PDA form a hydrophobic protective layer on the substrate surface.

[0029] (4) The EP-0.5wt%BPB coating of the present invention, based on the dual corrosion inhibition of PDA and BTA combined with the physical barrier of BNNS, endows the EP-0.5wt%BPB composite coating with excellent corrosion resistance. Tafel test results show that after immersion in 3.5wt% NaCl solution for 30 days, I corr 1.07×10 -9 Acm - 2. The corrosion inhibition efficiency (η2%) is 98.67%, C rate As low as 1.25×10 -5 mm / year. Scratch immersion testing showed a 67-fold improvement in protective performance compared to blank epoxy. EIS testing further demonstrated that the |Z| of the EP-0.5wt% BPB coating was significantly improved after 30 days. 0.01Hz (1.41×10 -10 ohm cm 2 The protection efficiency of the BPB-based EP coating is two orders of magnitude higher than that of the reference epoxy coating, reaching 98.62%. Furthermore, compared to H-BN, BPB exhibits a 58.70% higher UV absorption rate, resulting in excellent UV aging resistance for the EP-0.5wt% BPB coating. This enhances the coating's durability, ensuring stability under prolonged exposure and making it suitable for in-situ corrosion protection in offshore installations. Attached Figure Description

[0030] Figure 1 This is a scanning electron microscope image of BPB.

[0031] Figure 2 The Fourier transform infrared spectrum of each nanocomposite material is shown.

[0032] Figure 3 The image shows a partial Fourier transform infrared spectrum of BPB as a function of temperature, where (a,c) represents -OH and (b,d) represents -NH.

[0033] Figure 4 This is a graph showing the release response of BPB under different pH conditions.

[0034] Figure 5 This is a schematic diagram illustrating the mechanism of pH-sensitive release behavior of BPB.

[0035] Figure 6 Tafel results after immersion in different coatings for 30 days;

[0036] Figure 7 Scratch patterns of (a) EP coating and (b) EP-0.5wt% BPB coating after immersion in 5.0wt% solution for different times, and the corresponding water contact angle (WCA) after immersion, where the black line is the auxiliary line before scratching.

[0037] Figure 8 Schematic diagrams showing the immersion times of (a) EP coating and (b) EP-0.5wt%BPB coating at different times.

[0038] Figure 9 Physical images and water contact angles of (a) EP coating and (b) EP-0.5wt%BPB coating under UV irradiation. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings.

[0040] In the following examples, H-BN (5–10 μm) was purchased from Shanghai Yi'en Chemical Technology Co., Ltd. Bisphenol A diglycidyl ether (DGEBAE44, EP equivalent: 210–230 g / mol) was purchased from Nantong Xingchen Synthetic Materials Co., Ltd. Polyamide PA650 (amine value: 220 ± 20 mg KOH / g) was purchased from Dingyuan Danbao Resin Co., Ltd. Ethylene glycol, DMF, and dopamine hydrochloride (DA) were supplied by Shanghai Aladdin Biochemical Technology Co., Ltd. Tris(hydroxymethyl)aminomethane hydrochloride (TrB-HCl) and benzotriazole (BTA) were obtained from Tianjin Xiens Biochemical Technology Co., Ltd. Ethanol and sodium chloride were obtained from Shanghai Guoyao Chemical Reagent Co., Ltd. HCl and NaOH for pH adjustment were provided by the Nanjing University of Science and Technology Reagent Library. All reagents were untreated.

[0041] The preparation of the hydroxylated boron nitride nanosheets (BNNS) described in this invention is referenced in the literature (Wang Dong, Liu Dingyao, Xu Jianhua, et al., Highly thermoconductive yet ultraflexible polymer composites with superior mechanical properties and autonomous self-healing functionality via a binary filler strategy, Mater. Horiz., 2022, 9, 640-652), specifically:

[0042] Mix 1 g H-BN, 5 mL ethylene glycol, and 30 mL DMF. Sonicate the mixture for 6 h, then centrifuge at 2000 rpm for 5 min, discarding the bottom layer. Collect the supernatant and centrifuge again at 8000 rpm for 10 min, retaining the precipitate. Wash the precipitate with H2O and filter, then dry at 60 °C for 5 h to obtain hydroxylated boron nitride nanosheets.

[0043] Example 1

[0044] 1. Fabrication of the intelligent nanocontainer BPB:

[0045] (1) Self-polymerization of the sensitive PDA layer on BNNS nanosheets: 0.1 g BNNS was added to 150 mL of water and sonicated for 2 h to form a homogeneous suspension. Then 726 mg TrB-HCl was added. Subsequently, the pH was adjusted to 8.5 and 1.2 g dopamine was added. The mixture was stirred at ambient temperature in a dark environment for 12 h. The gray-black solution was centrifuged at 8000 rpm for 10 min and washed with H2O to obtain BNNS / PDA nanomaterials, abbreviated as BP.

[0046] (2) Adsorption of corrosion inhibitor BTA: BP was placed in an ethanol solution containing 4g of BTA dissolved in 50mL of 80mg / mL, and the adsorption reaction was carried out under vacuum at ambient temperature for 12h. After washing with H2O and centrifuging again, the intelligent nanocontainer BNNS / PDA / BTA, abbreviated as BPB, was obtained.

[0047] 2. Preparation of BPB-reinforced epoxy resin coating on Q235 carbon steel surface:

[0048] (1) Before use, the Q235 carbon steel substrate is polished with sandpaper of different grits, then rinsed three times with H2O and ethanol, and then dried at ambient temperature.

[0049] (2) Add 20 mg of the smart nanocontainer BPB to 5 mL of ethanol and sonicate for 20 min. Then mix the solution with 4 g of epoxy resin E44 and stir evenly for 30 min. The mass of BPB is 0.5% of the mass of E44. Then remove the excess solvent by rotary evaporation.

[0050] (3) Then add 4g of PA650 curing agent to the mixture and continue stirring for 20min. To ensure the coating is densified, the mixture is degassed for 10min. Finally, apply the coating to the pretreated substrate using a rod coater.

[0051] (4) The sample was cured at ambient temperature for 48 hours and then heated at 70°C for 12 hours to form an EP-0.5wt% BPB coating.

[0052] Comparative Example 1

[0053] Preparation of a pure epoxy resin control coating:

[0054] (1) Before use, the Q235 carbon steel substrate is polished with sandpaper of different grits, then rinsed three times with H2O and ethanol, and then dried at ambient temperature.

[0055] (2) Add 4g of PA650 curing agent to epoxy resin E44 and continue stirring for 20min. To ensure coating densification, the mixture is degassed for 10min. Finally, apply the coating to the pretreated substrate using a rod coater.

[0056] (3) The sample was cured at ambient temperature for 48 hours and then heated at 70°C for 12 hours to form an EP coating.

[0057] Comparative Example 2

[0058] This comparative example is basically the same as Example 1, except that PDA and BTA are not added. Compared with pure EP, the resulting epoxy coating has good barrier properties, which inhibits the penetration of electrolytes and the corrosion propagation phenomenon to a certain extent. However, since dual corrosion inhibition cannot be achieved, when the coating is damaged, although the local impedance shows a decreasing trend and the diffusion of corrosion reaction is inhibited to a certain extent, the degree of inhibition is not as strong as that of Example 1.

[0059] like Figure 1 As shown, the intelligent nanocontainer BPB was successfully prepared.

[0060] like Figure 2 As shown, H-BN at 1375cm -1 and 814cm -1 There are distinct absorption peaks at 3642 cm⁻¹, corresponding to the in-plane extension vibration of BN and the out-of-plane bending vibration of BNB, respectively. Furthermore, BNNS shows a peak at 3642 cm⁻¹. -1The strong absorption peaks nearby indicate the participation of OH stretching vibrations, suggesting the formation of β-OH bonds. (1600 cm⁻¹) -1 The absorption bands at this location originate from overlapping NH bending vibrations and CN ring stretching vibrations, indicating effective PDA deposition on BNNS. (1378 cm⁻¹) -1 The peaks at 1288, 1209, and 1112 cm⁻¹ indicate the bending and stretching of phenolic -OH groups, while the peaks at 1288, 1209, and 1112 cm⁻¹ represent the bending and stretching of phenolic -OH groups. -1 The peak at [value] indicates tertiary amine and -CO extension, confirming the self-polymerization of DA on BNNS. For BTA, [value] is 2500 to 3400 cm⁻¹. -1 The broad, multi-peak bands between them are strong NHH hydrogen bonds. (1209 cm⁻¹) -1 The peak value is related to the N=N bending, while the 742cm peak value in BPB is related to the bending of N=N. -1 The stripe represents the signal of the BTA load.

[0061] like Figure 3 As shown, temperature-dependent Fourier transform infrared analysis indicates that as temperature increases, the -OH peak decreases from 3737 cm⁻¹. -1 Gradually moved to 3742cm -1 The -NH peak starts at 1594 cm⁻¹ -1 Gradually moved to 1604cm -1 Meanwhile, the peak intensity also increased. This indicates that interfacial hydrogen bonds formed between BNNS and PDA, as well as between PDA and BTA.

[0062] like Figure 4 As shown, the kinetic release chemiluminescence (BTA) curves were monitored in real time. BTA exhibited controllable release under both acidic and alkaline stimuli. In the pH 7.0 test environment, although some BTA was released, the total release amount was low after 780 min, with a cumulative release rate of 22.15%. In the pH 2.0 test environment, the cumulative release rate of BTA was 32.40% after 780 min. In the pH 11.0 test environment, the cumulative release rate of BTA was 25.28% after 780 min. Notably, BTA release continued even after 780 min.

[0063] like Figure 5As shown, the controlled release mechanism of BPB can be deduced based on the amino and phenolic hydroxyl groups. In neutral solution, PDA attaches functional ligands to the BNNS surface through physical interactions (hydrogen bonds, π-π stacking) or chemical bonds (Michael addition or Schiff base reactions). More importantly, physical bonds (hydrogen bonds, π-π stacking) also exist between PDA and BTA. In an acidic environment (pH=2), electrostatic repulsion occurs because both BTA and PDA are positively charged. Under alkaline conditions (pH=11), BTA is negatively charged, while PDA is also negatively charged due to its high hydroxyl content. That is, the electrostatic repulsion between the two leads to a significant enhancement in the release behavior of BTA at acidic / alkaline pH. Furthermore, PDA is unstable in acidic environments. This may be related to the ring-closing step in the polymerization process and the increased -NH2 content. This also contributes to the release of BTA. Therefore, by utilizing the changes in amino and hydroxyl charge with pH, ​​the release behavior of the PDA sensitive layer system can be customized according to a specific pH value.

[0064] like Figure 6 As shown, the E values ​​of bare EP and EP-0.5wt% BPB samples are... corr The values ​​were -0.78V and -0.37V respectively, and gradually shifted towards the positive direction. corr From 8.03×10 -8 A·cm -2 (EP) decreased to 1.07×10 -9 A·cm -2 (EP-0.5wt%BPB), indicating that the EP-0.5wt%BPB coating has a low tendency for hot corrosion. The R of the EP-0.5wt%BPB coating... p The maximum value is 4.37 × 10. 7 ohm·cm -2 ), compared to EP (7.30×10 5 ohm·cm -2 This is two orders of magnitude higher than the reference EP (9.33 × 10⁻⁶). -4 Compared to (mm / year), the EP-0.5wt% BPB coating exhibits lower C. rate (1.25×10 -5 These findings indicate that the EP-0.5wt%BPB coating, employing a synergistic active and passive corrosion protection strategy, can effectively block the entry of corrosive substances, thereby improving the corrosion resistance of the substrate.

[0065] like Figure 7 As shown, the scratched coating was immersed in a 5.0 wt% sodium chloride environment to simulate the short-term degradation process of the coating in a natural environment. All the scratched and damaged coatings showed varying degrees of corrosion products. (Refer to EP coating...) Figure 7a) By day 30, large areas of black residue began to appear on the coating. At this point, the coating had failed. In contrast, the EP-0.5wt% BPB coating ( Figure 7 b) Corrosion products did not begin to spread in a small area of ​​the coating scratch until day 30. The area percentages of corrosion products on the coating, calculated using ImageJ software, were 0.53% and 33.27%, respectively. In other words, the risk of corrosion of the damaged EP-0.5wt%BPB coating was reduced to 67 times its original value within 30 days.

[0066] like Figure 8 As shown, EIS testing further indicates that after 30 days, the |Z| of the EP-0.5wt% BPB coating... 0.01Hz (1.41×10 -10 ohm cm 2 The BPB-based EP coating achieves a protection efficiency of 98.62%, which is two orders of magnitude higher than the reference coating.

[0067] like Figure 9 As shown, the water contact angle of the EP coating increased slightly after UV aging. This is likely due to aging phenomena such as micropore formation on the epoxy resin surface during irradiation. Furthermore, the water contact angle of the EP-0.5wt%BPB coating remained consistently higher than that of the EP coating. This means that adding a lower amount of BPB can enhance the hydrophobic properties of the EP coating and ensure stability throughout the UV irradiation process.

Claims

1. A method for preparing an acid-base responsive boron nitride nanoreservoir driven self-healing and anti-aging synergistic anticorrosion coating, characterized in that, Includes the following steps: (1) Self-polymerization of sensitive layer PDA on BNNS nanosheets: Tris(hydroxymethyl)aminomethane hydrochloride was added to a suspension of hydroxylated boron nitride nanosheets, the pH was adjusted to 8.0~8.5, dopamine was added, the reaction was stirred in the dark, and after the reaction was completed, the nanosheets were centrifuged and washed to obtain BNNS / PDA nanomaterials. (2) Adsorption of corrosion inhibitor BTA: BNNS / PDA nanosheets were added to a saturated benzotriazole ethanol solution and the adsorption reaction was carried out under vacuum. After the reaction was complete, the nanosheets were washed with water and centrifuged to obtain the smart nanocontainer BNNS / PDA / BTA. (3) Preparation of BPB-enhanced epoxy resin coating: The smart nanocontainer BNNS / PDA / BTA was ultrasonically dispersed in ethanol. Then, the ethanol dispersion of the smart nanocontainer BNNS / PDA / BTA was mixed with the epoxy resin at a mass of 0.5 ± 0.1% of the epoxy resin mass. The mixture was stirred until homogeneous, and then the excess solvent was removed by rotary evaporation. A curing agent was added to the mixture, and the reaction was continued to make the coating dense. After degassing, the EP-BPB coating was obtained.

2. The preparation method according to claim 1, characterized in that, In step (1), the preparation method of hydroxylated boron nitride nanosheets is as follows: hexagonal boron nitride nanosheets are exfoliated and surface hydroxylated by liquid phase ultrasonic exfoliation. Hexagonal boron nitride nanosheets, ethylene glycol and DMF are mixed and ultrasonically exfoliated. Then, the supernatant is collected by centrifugation, centrifugation is performed again, the precipitate is collected, the precipitate is washed with water and filtered, and dried to obtain hydroxylated boron nitride nanosheets.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of hydroxylated boron nitride nanosheets to dopamine is 0.4~0.9:

1.

4. The preparation method according to claim 1, characterized in that, In step (1), the centrifugation speed is 8000~10000 rpm and the centrifugation time is 10~15 min.

5. The preparation method according to claim 1, characterized in that, In step (2), the concentration of benzotriazole in the ethanol solution is 80 mg / mL.

6. The preparation method according to claim 1, characterized in that, In step (2), the adsorption reaction time is more than 12 hours.

7. The preparation method according to claim 1, characterized in that, In step (3), the concentration of the intelligent nanocontainer BNNS / PDA / BTA in the ethanol dispersion is 20 mg / mL.

8. The coating prepared by any one of claims 1 to 7.

9. The application of the coating according to claim 8 in metal corrosion protection.

10. The application according to claim 9, characterized in that, The metal is Q235 carbon steel, magnesium alloy, aluminum alloy or brass.

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