Functionalized boron nitride epoxy composite anti-corrosion coating for load coupling corrosion environment as well as preparation method and application of functional boron nitride epoxy composite anti-corrosion coating

Abstract

The invention relates to a functionalized boron nitride epoxy composite anticorrosive coating used in a load coupling corrosion environment, the functionalized boron nitride epoxy composite anticorrosive coating comprises functionalized boron nitride and epoxy resin, the functionalized boron nitride is a dopamine functionalized boron nitride nano material obtained by modifying boron nitride with dopamine, and the epoxy resin is a modified epoxy resin. The modification treatment is characterized in that dopamine and boron nitride are mixed in an ethanol solution for modification by adopting an oxidation method and a nucleophilic reaction method; the dopamine functionalized boron nitride nano material is uniformly dispersed in epoxy resin to form a compact structure. The invention further provides the functionalized boron nitride epoxy composite anticorrosive coating as well as a preparation method and application thereof. The problem that an existing epoxy coating is insufficient in physical barrier property and corrosion resistance is successfully solved, the service life of the epoxy coating is greatly prolonged, and the epoxy coating can be used for the complex service environment with the load and corrosion environment coupling effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal anti-corrosion coatings, and in particular relates to a functionalized boron nitride epoxy composite anti-corrosion coating and a preparation method and application thereof. Background Art

[0002] Applying corrosion-resistant coatings to metal substrates has proven to be one of the most effective, cost-effective, and convenient methods for metal corrosion protection. This is primarily due to the barrier effect of the coating, which prevents the metal from coming into contact with the external environment, thereby preventing corrosion. Among corrosion-resistant coatings, epoxy resins are widely used for metal corrosion protection in the marine engineering sector due to their excellent wear resistance, adhesion, stability in acidic and alkaline conditions, and high economic benefits.

[0003] Typical epoxy resins act as a physical barrier, preventing corrosive media from diffusing to the metal surface. However, the epoxy resin curing process inevitably creates numerous micropores in the coating. Furthermore, the epoxy resin coating's weak mechanical properties lead to microcracks during use, making it particularly difficult to withstand the combined effects of load and corrosive environments. Corrosive media (chloride ions, moisture, etc.) penetrate the coating / metal interface through the micropores and cracks induced by sustained loads, reducing the adhesion between the epoxy coating and the metal substrate, degrading the coating's corrosion resistance, and accelerating corrosion of the metal substrate. Therefore, a coating that can simultaneously withstand both load and environmental corrosion is needed to improve its corrosion resistance.

[0004] Chinese patent CN11214338B discloses a dopamine-functionalized graphene steel bar anti-corrosion coating material and its preparation method. This coating uses electrophoretic deposition technology to construct an electrochemical reaction system, energizing it to deposit epoxy resin on the substrate surface. Cyclic voltammetry is then used to deposit the dopamine-functionalized graphene material onto the surface of the water-based resin layer to form a graphene anti-corrosion coating. The coating preparation method is complex and requires strict process technology, making it unsuitable for industrial production. Chinese patent CN115322654A discloses a method for preparing a nano-thermal conductive ceramic anti-wear and anti-corrosion coating. By adding raw materials such as calcium fluoride, aluminum oxide, silicon oxide, ferric oxide, and sodium silicate, the coating has excellent corrosion resistance and adhesion. Chinese patent CN114479619A discloses a method for preparing a polysulfide rubber-modified epoxy resin anti-corrosion coating. The polysulfide rubber-modified epoxy resin obtained under the catalysis of triphenylphosphine reduces the water absorption rate of the coating. In 2023, Zhong Xiankang et al. published a paper titled "Unmasking the delamination mechanisms of adefective coating under the co-existence of alternating stress and corrosion," and in 2024, Dong Zheng et al. published a paper titled "Unmasking the degradation of epoxy coating on the surface of steel subjected to stress in simulated concrete pore solution." Both papers show that the combined effects of load and corrosive environment increase the coating's moisture diffusion coefficient, significantly reduce the coating's impedance, reduce the coating's corrosion resistance, and significantly shorten the metal substrate's rusting time. Marine engineering structures are subjected to the coupled effects of load and corrosive environment for long periods of time in their service environment. However, the above patents focus primarily on the corrosion resistance of the coating in a single corrosive environment and do not consider the impact of load. Therefore, they do not significantly improve the corrosion resistance of marine engineering structures.

[0005] Boron nitride, as a two-dimensional nanomaterial, can be added to epoxy resin in an appropriate amount to give it higher mechanical properties and excellent anti-permeability. At the same time, due to its unique insulation properties, it does not cause galvanic corrosion compared to graphene materials, and has great application prospects in the field of composite anti-corrosion coatings, especially in compensating for the weakness of insufficient mechanical properties of epoxy coatings. For example, Chinese patent CN117363140A discloses a wide-temperature range self-lubricating coating with boron nitride / graphene composite filler and its preparation method. This coating improves the adhesion and tribological properties of the coating by changing the filling amount of boron nitride / graphene composite material in epoxy resin. Chinese patent CN118063979A discloses a dopamine-modified nano-boron nitride and its preparation method. This coating is in the dopamine-modified boron nitride stage. By changing the water bath stirring treatment time, the dopamine grafting rate is varied, thereby improving the thermal conductivity of the coating. Chinese patent CN116285576B discloses a water-based epoxy-modified boron nitride nano-composite coating and its preparation method. The method is to modify the amount of boron nitride added to the epoxy resin to obtain good physical barrier properties and corrosion resistance. Chinese patent CN106987164B discloses a method for preparing a boron nitride-graphene oxide composite anti-corrosion filler, the main feature of which is to add graphene oxide to boron nitride and change the mass ratio of boron nitride and graphene, thereby reducing the interface defects in the epoxy coating and improving the anti-corrosion performance of the coating. However, the above patents mainly focus on improving the coating formula and do not make functional improvements to the coating. They fail to effectively solve the dispersibility and compatibility problems of boron nitride in epoxy; at the same time, they fail to consider the impact of the load-coupled corrosion environment on it, which casts a question mark on the application of boron nitride epoxy composite anti-corrosion materials in the actual field of anti-corrosion coating technology.

[0006] In summary, the current field of metal anti-corrosion coatings faces two major problems that need to be solved urgently. The first is how to improve the mechanical properties of epoxy coatings and their density under external loads, so that they can effectively resist the coupling of loads and corrosive environments. The second is that due to the stability of its internal structure and the lack of active groups on the surface, boron nitride has extremely poor compatibility with epoxy resins and is very easy to agglomerate, which makes it difficult to resist the invasion of corrosive media for a long time, thereby limiting its application in the engineering field. How to improve the dispersibility of boron nitride nanomaterials in epoxy coatings, thereby reducing the interface defects of epoxy coatings and improving interface compatibility. In view of this, there is an urgent need to develop a functionalized boron nitride epoxy composite anti-corrosion coating suitable for load-coupled corrosion environments to overcome the problem of insufficient durability of the coating under stress and corrosive environments. Summary of the Invention

[0007] In order to overcome the shortcomings of existing epoxy coatings in terms of poor corrosion resistance under load and in marine environments, the present invention provides a functionalized boron nitride epoxy composite anti-corrosion coating for load-coupled corrosion environments, and its preparation method and application. Based on boron nitride composite epoxy materials, a functionalized boron nitride / epoxy composite anti-corrosion coating is prepared to improve the mechanical properties of the coating and its corrosion protection performance in a load-coupled corrosion environment; at the same time, the compatibility of boron nitride in epoxy resin is improved through functionalization treatment. The corrosion resistance of the metal anti-corrosion coating of the present invention is significantly improved compared to that of ordinary epoxy coatings. Even under the dual effects of load and corrosive environment, the coating can still maintain excellent anti-corrosion effect, successfully solving the problem of insufficient physical barrier and corrosion resistance of existing epoxy coatings, thereby greatly extending the service life of the epoxy coating, and can be used in complex service environments with coupled load and corrosive environment.

[0008] The technical solution adopted by the present invention to solve its technical problem is:

[0009] A functionalized boron nitride-epoxy composite anti-corrosion coating for use in load-coupled corrosion environments. The functionalized boron nitride-epoxy composite anti-corrosion coating comprises functionalized boron nitride and epoxy resin. The functionalized boron nitride is modified by using dopamine to obtain a dopamine-functionalized boron nitride nanomaterial. The modification is performed by mixing the dopamine and boron nitride in an ethanol solution using an oxidation method and a nucleophilic reaction method. The dopamine-functionalized boron nitride nanomaterial is uniformly dispersed in the epoxy resin to form a dense structure.

[0010] Furthermore, in the functionalized boron nitride nanomaterial, dopamine serves as a modifier and boron nitride serves as a modified substance. The functionalized boron nitride is a two-dimensional nanomaterial formed by dopamine polymerization and grafting onto the surface of boron nitride.

[0011] More preferably, the modification method is non-covalent modification, that is, the boron nitride surface is functionalized through the van der Waals force, hydrogen bond and π-π bond of dopamine.

[0012] The preparation process of the dopamine functionalized boron nitride nanomaterial is as follows:

[0013] First, boron nitride powder is added to a sodium hydroxide solution, stirred for reaction, and filtered, washed, and dried to obtain hydroxylated boron nitride powder;

[0014] Secondly, dopamine and hydroxylated boron nitride powder are uniformly dispersed in tris(hydroxymethylaminomethane) hydrochloric acid buffer with a pH value of 8 to 8.5 through thermal oxidation reaction and nucleophilic reaction and are fully mixed. The boron nitride is functionalized by ultrasonic dispersion for 2 to 3 hours and heating with magnetic stirring in a water bath for full reaction. Polydopamine-modified boron nitride nanosheets are obtained by filtration, washing and drying.

[0015] Preferably, the particle size of the boron nitride powder is 0.1-0.4 μm.

[0016] The mass ratio of the dopamine to the hydroxylated boron nitride is 1:1 to 1:2.5.

[0017] The water bath heating temperature is 50 to 60 degrees Celsius, and the heating time is 12 to 24 hours.

[0018] The drying temperature is 50 to 60 degrees Celsius, and the drying time is 12 to 24 hours.

[0019] The anti-corrosion performance mechanism of the dopamine-functionalized boron nitride-epoxy composite anti-corrosion coating of the present invention in a load-coupled corrosion environment and its barrier effect on corrosive media are as follows: the dopamine-functionalized boron nitride nanomaterial is uniformly dispersed in the epoxy resin due to the interaction between hydrogen bonds and π-π bonds, which helps to give full play to the high aspect ratio advantage of boron nitride, thereby forming a "maze effect" inside the epoxy resin, effectively blocking the penetration of corrosive media (see Figure 1 Boron nitride, with its unique insulating properties, avoids direct contact with the metal substrate, thereby shielding against galvanic corrosion. Furthermore, dopamine acts as a binder, significantly improving the interfacial compatibility and adhesion between boron nitride and epoxy resin, thereby enhancing the mechanical properties of the epoxy resin and effectively reducing the potential for pore growth under stress, preventing the resulting expansion of corrosion channels and thus enhancing the coating's anti-corrosion effectiveness.

[0020] A method for preparing a functionalized boron nitride epoxy composite anti-corrosion coating for a load-coupled corrosive environment comprises the following steps:

[0021] 1) Grinding: Weigh the functionalized boron nitride powder and grind it into powder;

[0022] 2) Preparing a mixture: adding functionalized boron nitride to an anhydrous ethanol solution, ultrasonically dispersing for 2-3 hours in an ultrasonic disperser to obtain a boron nitride dispersion, adding epoxy resin to the dispersion and ultrasonicating again for 20-30 minutes;

[0023] 3) Water bath thermal reaction: The mixed solution obtained in step 2) is subjected to rotary evaporation of ethanol at a temperature of 60 to 70 degrees Celsius under a vacuum environment to obtain an epoxy mixed solution;

[0024] 4) Vacuum curing: reacting the epoxy mixture obtained in step 3) with a curing agent under vacuum pressure of 60 to 70 degrees Celsius for 30 to 60 minutes to remove bubbles and obtain an epoxy resin coating, i.e., a functionalized boron nitride epoxy composite anti-corrosion coating.

[0025] In the functionalized boron nitride epoxy composite anti-corrosion coating, the mass ratio of each component is:

[0026]

[0027] In the step 3), the rotation speed of the rotary evaporator is 20 to 280 rpm, and the reaction time is 40 to 60 minutes.

[0028] The method further comprises the following steps:

[0029] 5) Metal substrate pretreatment: Prepare a metal substrate with a size of (1-5) x (1-15) cm 2 The steel sheet was polished on 100-2000 grit sandpaper and then ultrasonically cleaned in ethanol and acetone solution for 20-30 minutes, and finally the liquid on the surface of the steel sheet was blown dry with nitrogen;

[0030] 6) coating: coating the coating obtained in step 4) on the metal substrate;

[0031] 7) Curing: The applied coating is cured at room temperature for 18 to 24 hours and then at 50 to 60 degrees Celsius for 2 to 4 hours to obtain a metal anti-corrosion coating and a metal product with the metal anti-corrosion coating.

[0032] In the step 7), the thickness of the composite coating is 200 to 250 μm.

[0033] In the step 6), the coating method is a roller coating method, wherein the coating is evenly applied on the surface of the substrate by the rotation and pressure of the roller coating roller, and the speed of the roller coating machine is 6 to 15 meters per minute.

[0034] In step 5), the metal substrate includes but is not limited to iron, steel, copper and other metal materials. The metal products can be in various shapes, for example, the shape of iron products includes but is not limited to plate, rod and the like.

[0035] The invention discloses an application of a functionalized boron nitride epoxy composite anti-corrosion coating for load-coupled corrosion environment, which is used for civil buildings, pipelines, new energy power generation, offshore wind power or marine oil platforms under the coupling of load and corrosion environment.

[0036] The beneficial effects of the present invention are mainly manifested in: 1) The present invention comprehensively considers the enhancement of the mechanical properties of the coating and the reduction of the porosity, and increases the mechanical properties of the coating by modifying the epoxy resin with boron nitride. At the same time, starting from the dopamine grafting rate of dopamine-functionalized boron nitride, the coating is made denser and free of through holes through the uniform dispersion of functionalized boron nitride. The porosity of the coating in the present invention is 0.0215%, which is significantly lower than that of ordinary epoxy coatings (0.139%). The joint improvement of mechanical properties and density enables the coating to be effectively used in complex service conditions of load-coupled corrosion environments. Applying the dopamine-functionalized boron nitride composite epoxy resin coating to the surface of metal products significantly improves its scope of application and service life under load and corrosion environment coupling conditions. The coating impedance of the coating under stress conditions in the present invention is significantly higher than that of ordinary epoxy coatings. 2) The dopamine-functionalized boron nitride nanomaterial provided by the present invention effectively improves the inertness of the boron nitride surface. Dopamine acts as a binder, imparting surface active functional groups to boron nitride, thereby improving the interfacial compatibility between epoxy resin and boron nitride and reducing agglomeration. 3) Due to the interaction between hydrogen bonds and π-π bonds, the dopamine-functionalized boron nitride sheet structure in the present invention can form an effective barrier layer in the anti-corrosion coating, effectively hindering the penetration of corrosive media (such as water, oxygen, chloride ions, etc.), and giving full play to the physical isolation effect of boron nitride. 4) The uniform dispersion of the dopamine-functionalized boron nitride material provided by the present invention in the anti-corrosion coating significantly extends the diffusion path of the corrosive medium. At the same time, the functionalized boron nitride epoxy resin composite anti-corrosion coating utilizes the insulating properties of boron nitride as a barrier layer to avoid direct contact with the metal substrate, thereby shielding galvanic corrosion. 5) The preparation method of the anti-corrosion coating provided by the present invention is simple, low-cost, low in energy consumption, low in pollution, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a diagram of the anti-corrosion mechanism for preparing functionalized boron nitride-epoxy composite coatings.

[0038] Figure 2 These are scanning electron microscope morphology images of the functionalized boron nitride nanomaterials of Examples 1 to 4 and the boron nitride before functionalization, wherein (a) is Example 1, (b) is Example 2, (c) is Example 3, (d) is Example 4, and (e) is the boron nitride before functionalization.

[0039] Figure 3 This is a graph showing the ultimate strength results of the epoxy resin material and the functionalized boron nitride epoxy composite material in Examples 1 to 4.

[0040] Figure 4 Graphs of coating impedance at 0.01 Hz are shown for the coated steel products of Comparative Examples 1 to 4. DETAILED DESCRIPTION

[0041] The present invention will be further described below with reference to the accompanying drawings.

[0042] Reference Figures 1 to 4 A functionalized boron nitride-epoxy composite anti-corrosion coating for load-coupled corrosion environment, the functionalized boron nitride-epoxy composite anti-corrosion coating comprising functionalized boron nitride and epoxy resin, the functionalized boron nitride being modified by dopamine to obtain dopamine-functionalized boron nitride nanomaterial, the modification being modified by mixing the dopamine and boron nitride in an ethanol solution using an oxidation method and a nucleophilic reaction method; the dopamine-functionalized boron nitride nanomaterial being uniformly dispersed in the epoxy resin to form a dense structure.

[0043] Examples 1-4 demonstrate functionalized boron nitride-epoxy composite anticorrosion materials with varying dopamine and boron nitride ratios. Comparative Examples 1 and 2 demonstrate epoxy-coated steel products under different load levels. Comparative Examples 3 and 4 demonstrate the operating conditions of functionalized boron nitride-epoxy composite-coated steel products under different load levels after selecting the appropriate ratios.

[0044] Example 1

[0045] A method for preparing a functionalized boron nitride epoxy composite anti-corrosion coating for a load-coupled corrosive environment comprises the following steps:

[0046] (1) 3 g of hexagonal boron nitride powder was dispersed in 100 ml of 5 mol / L sodium hydroxide solution. After dispersion, the mixture was transferred to a polytetrafluoroethylene autoclave and reacted at 120 degrees Celsius for 24 hours. The mixture was then repeatedly washed with deionized water until neutral. The resulting product was dried in a vacuum oven at 80 degrees Celsius for 24 hours to obtain hydroxylated boron nitride powder.

[0047] (2) 0.726 g of tris(hydroxymethyl)aminomethane was added to 600 ml of anhydrous ethanol solution, and then 0.1 mol / L of dilute hydrochloric acid was added to adjust the pH value to 8.5. Subsequently, 1.2 g of dopamine hydrochloride was added, and the mixture gradually turned gray. Subsequently, 1.2 g of boron nitride in step (1) was added, and the mixture was ultrasonically treated for 3 hours, and then reacted at 60 degrees Celsius for 24 hours, filtered, and washed with deionized water several times until the filtrate was colorless. The gray product was then vacuum dried at 80 degrees Celsius for 1 hour to obtain a polydopamine-modified boron nitride nanomaterial, wherein the mass ratio of dopamine hydrochloride to hydroxylated boron nitride was 1:1, and the number was recorded as PBN1.0.

[0048] (3) Weigh the functionalized boron nitride powder in step (2) and grind it into powder.

[0049] (4) Add the functionalized boron nitride to the anhydrous ethanol solution and ultrasonically disperse it in an ultrasonic disperser for 2 hours to obtain a boron nitride dispersion. Add the epoxy resin to the above dispersion and ultrasonicate it again for 30 minutes.

[0050] (5) The obtained mixed solution was subjected to rotary evaporation of ethanol at 70 degrees Celsius under a vacuum environment at a rotation speed of 200 revolutions per minute for 1 hour to obtain an epoxy mixed solution.

[0051] (6) The obtained epoxy mixture and curing agent are cured under vacuum vacuum pumping at a curing temperature of 60 degrees Celsius for 60 minutes to remove bubbles and obtain a boron nitride epoxy composite coating.

[0052] (7) The size is 4×12cm 2 The steel sheets were polished on 100 mesh, 500 mesh, 1000 mesh and 2000 mesh sandpapers, and then ultrasonically cleaned in ethanol and acetone solution for 30 minutes, and finally the liquid on the surface of the steel sheets was blown dry with nitrogen.

[0053] (8) Coating: The obtained coating was poured into a tensile mechanical mold to prepare a coating for mechanical strength testing; at the same time, it was coated on a steel sheet. The coated coating was cured under certain conditions to obtain a modified boron nitride metal anti-corrosion coating with a mass fraction of 1% and a metal product with the metal anti-corrosion coating, which were designated as EpBN1.0.

[0054] Example 2

[0055] The only difference from Example 1 is that in the dopamine-modified nano-boron nitride powder prepared in Example 2, the mass ratio of dopamine hydrochloride to hydroxylated boron nitride powder is 1:1.5 during the dopamine modification stage.

[0056] The preparation method comprises the following steps:

[0057] (1) 3 g of hexagonal boron nitride powder was dispersed in 100 ml of 5 mol / L sodium hydroxide solution. After dispersion, the mixture was transferred to a polytetrafluoroethylene autoclave and reacted at 120 degrees Celsius for 24 hours. The mixture was then repeatedly washed with deionized water until neutral. The resulting product was dried in a vacuum oven at 80 degrees Celsius for 24 hours to obtain hydroxylated boron nitride powder.

[0058] (2) 0.726 g of tris(hydroxymethyl)aminomethane was added to 600 ml of anhydrous ethanol solution, followed by the addition of 0.1 mol / L dilute hydrochloric acid to adjust the pH to 8.5. 1.2 g of dopamine hydrochloride was then added, and the mixture gradually turned gray. 1.8 g of the boron nitride prepared in step (1) was then added, and the mixture was ultrasonically treated for 3 hours. The mixture was then reacted at 60 degrees Celsius for 24 hours, filtered, and washed several times with deionized water until the filtrate was colorless. The gray product was then vacuum dried at 80 degrees Celsius for 1 hour to obtain a polydopamine-modified boron nitride nanomaterial, designated as PBN1.5.

[0059] (3) Weigh 0.5 g of the functionalized boron nitride powder prepared in step (2) and grind it into powder.

[0060] (4) Add the functionalized boron nitride to the anhydrous ethanol solution and ultrasonically disperse it for 2 hours in an ultrasonic disperser to obtain a boron nitride dispersion. Add 40 grams of epoxy resin to the above dispersion and ultrasonicate it again for 30 minutes.

[0061] (5) The obtained mixed solution was subjected to rotary evaporation of ethanol at 70 degrees Celsius under a vacuum environment at a rotation speed of 200 revolutions per minute for 1 hour to obtain an epoxy mixed solution.

[0062] (6) The obtained epoxy mixture was cured with 10 g of curing agent under vacuum vacuum pumping at a curing temperature of 60 degrees Celsius for 60 minutes to remove bubbles and obtain a boron nitride epoxy composite coating.

[0063] (7) The size is 4×12cm 2 The steel sheets were polished on 100 mesh, 500 mesh, 1000 mesh and 2000 mesh sandpapers, and then ultrasonically cleaned in ethanol and acetone solution for 30 minutes, and finally the liquid on the surface of the steel sheets was blown dry with nitrogen.

[0064] (8) Coating: The obtained coating was poured into a tensile mechanical mold to prepare a coating for mechanical strength testing; at the same time, it was coated on a steel sheet. The coated coating was cured under certain conditions to obtain a modified boron nitride metal anti-corrosion coating with a mass fraction of 1% and a metal product with the metal anti-corrosion coating, which were designated as EpBN1.5.

[0065] Example 3

[0066] The only difference from Example 1 is that in the dopamine-modified nano-boron nitride powder prepared in Example 3, the mass ratio of dopamine hydrochloride to hydroxylated boron nitride powder is 1:2 during the dopamine modification stage.

[0067] The preparation method comprises the following steps:

[0068] (1) 3 g of hexagonal boron nitride powder was dispersed in 100 ml of 5 mol / L sodium hydroxide solution. After dispersion, the mixture was transferred to a polytetrafluoroethylene autoclave and reacted at 120 degrees Celsius for 24 hours. The mixture was then repeatedly washed with deionized water until neutral. The resulting product was dried in a vacuum oven at 80 degrees Celsius for 24 hours to obtain hydroxylated boron nitride powder.

[0069] (2) 0.726 g of tris(hydroxymethyl)aminomethane was added to 600 ml of anhydrous ethanol solution, followed by the addition of 0.1 mol / L dilute hydrochloric acid to adjust the pH to 8.5. 1.2 g of dopamine hydrochloride was then added, and the mixture gradually turned gray. 2.4 g of the boron nitride prepared in step (1) was then added, and the mixture was ultrasonically treated for 3 hours. The mixture was then reacted at 60 degrees Celsius for 24 hours, filtered, and washed several times with deionized water until the filtrate was colorless. The gray product was then vacuum dried at 80 degrees Celsius for 1 hour to obtain a polydopamine-modified boron nitride nanomaterial, designated as PBN2.0.

[0070] (3) Weigh 0.5 g of the functionalized boron nitride powder prepared in step (2) and grind it into powder.

[0071] (4) Add the functionalized boron nitride to the anhydrous ethanol solution and ultrasonically disperse it for 2 hours in an ultrasonic disperser to obtain a boron nitride dispersion. Add 40 grams of epoxy resin to the above dispersion and ultrasonicate it again for 30 minutes.

[0072] (5) The obtained mixed solution was subjected to rotary evaporation of ethanol at 70 degrees Celsius under a vacuum environment at a rotation speed of 200 revolutions per minute for 1 hour to obtain an epoxy mixed solution.

[0073] (6) The obtained epoxy mixture was cured with 10 g of curing agent under vacuum vacuum pumping at a curing temperature of 60 degrees Celsius for 60 minutes to remove bubbles and obtain a boron nitride epoxy composite coating.

[0074] (7) The size is 4×12cm 2 The steel sheets were polished on 100 mesh, 500 mesh, 1000 mesh and 2000 mesh sandpapers, and then ultrasonically cleaned in ethanol and acetone solution for 30 minutes, and finally the liquid on the surface of the steel sheets was blown dry with nitrogen.

[0075] (8) Coating: The obtained coating was poured into a tensile mechanical mold to prepare a coating for mechanical strength testing; at the same time, it was coated on a steel sheet. The coated coating was cured under certain conditions to obtain a modified boron nitride metal anti-corrosion coating with a mass fraction of 1% and a metal product with the metal anti-corrosion coating, which were designated as EpBN2.0.

[0076] Example 4

[0077] The only difference from Example 1 is that in the dopamine-modified nano-boron nitride powder prepared in Example 4, the mass ratio of dopamine hydrochloride to hydroxylated boron nitride powder is 1:2.5 during the dopamine modification stage.

[0078] The preparation method comprises the following steps:

[0079] (1) 3 g of hexagonal boron nitride powder was dispersed in 100 mL of 5 mol / L sodium hydroxide solution, and after dispersion, it was transferred to a polytetrafluoroethylene autoclave and reacted at 120 °C for 24 hours. Then, it was repeatedly washed with deionized water until it was neutral, and the obtained product was dried in a vacuum oven at 80 °C for 24 hours to obtain hydroxylated boron nitride powder.

[0080] (2) 0.726 g of tris-hydroxymethyl aminomethane was added to 600 mL of anhydrous ethanol solution, and then 0.1 mol / L dilute hydrochloric acid was added to adjust the pH value to 8.5. Then, 1.2 g of dopamine hydrochloride mixture was added, and the mixture gradually turned gray. Then, 3 g of boron nitride in step (1) was added, and the mixture was ultrasonically treated for 3 hours, and then reacted at 60 °C for 24 hours. After filtration, it was washed with deionized water several times until the filtrate was colorless, and then the gray product was dried in a vacuum oven at 80 °C for 24 hours to obtain polydopamine modified boron nitride nanomaterial, numbered as PBN2.5.

[0081] (3) 0.5 g of functionalized boron nitride powder in step (2) was ground into powder.

[0082] (4) The functionalized boron nitride was added to anhydrous ethanol solution and ultrasonically dispersed in an ultrasonic disperser for 2 hours to obtain a boron nitride dispersion liquid. 40 g of epoxy resin was added to the above dispersion liquid and ultrasonically treated for 30 minutes again.

[0083] (5) The obtained mixture was rotary evaporated at 70 °C under vacuum environment, the rotary speed was 200 rpm, and the reaction time was 1 hour to obtain an epoxy mixture.

[0084] (6) The obtained epoxy mixture was vacuum degassed with 10 g of curing agent at 60 °C for 60 minutes to remove bubbles to obtain boron nitride epoxy composite coating.

[0085] (7) A steel sheet with a size of 4 x 12 cm 2 was polished on 100 mesh, 500 mesh, 1000 mesh, and 2000 mesh sandpaper, and then ultrasonically cleaned in ethanol ketone solution for 30 minutes, and finally the surface liquid of the steel sheet was blown dry with nitrogen.

[0086] (8) Coating: The obtained coating was poured into a tensile mechanics mold to prepare a coating for mechanical strength test, and at the same time, it was coated on a steel sheet. The coated coating was cured under certain conditions to obtain a modified boron nitride metal anticorrosion coating with a mass fraction of 1% and a metal product with a metal anticorrosion coating, numbered as EpBN2.5.

[0087] Figure 2The surface micromorphology of the functionalized boron nitride nanomaterials and the boron nitride before functionalization in Examples 1 to 4 of the present invention is shown. As can be seen from the figure, the boron nitride before functionalization shows obvious agglomeration. Compared with the boron nitride sample before functionalization, its agglomeration phenomenon has improved, indicating that dopamine grafting has effectively improved the layered stacking problem of boron nitride to a certain extent. This improvement is attributed to the dopamine molecules combining with the sheet structure of boron nitride through π-π bonds, which allows the boron nitride to be stably dispersed in the ethanol solution. Among them, the agglomeration phenomenon of Example 1 is significantly reduced, and the surface is more transparent and clear. In addition, a small amount of nano-sheet structures also appear.

[0088] Comparative Example 1

[0089] An epoxy coating, without any nanomaterials, was prepared by mixing commercially available epoxy resin and curing agent in a 4:1 ratio to create 50g of the epoxy resin coating and the coated steel product, designated EP. To simulate a real engineering structure, the coated steel product was immersed in a concrete pore solution for 14 days, followed by a 3.5% sodium chloride solution, and the immersion time was 14 days.

[0090] Comparative Example 2

[0091] An epoxy coating, without any nanomaterials, is prepared by mixing commercially available epoxy resin and curing agent in a ratio of 4:1, yielding 50g. This epoxy resin coating and coated steel product are designated EP. Unlike Comparative Example 1, Comparative Example 2 places the coated steel product on a self-developed loading device, subjecting it to an applied tensile stress of 60% of its yield strength. Under these stress conditions, the coated steel product is first immersed in a concrete pore solution for 14 days. Subsequently, a 3.5% sodium chloride solution (mass fraction) is added and immersed for another 14 days.

[0092] Comparative Example 3

[0093] Optimization was performed in Examples 1 to 4, and EpBN1.0 coated steel products were selected. The test process, duration, and stress state (no stress) were all consistent with those in Comparative Example 1.

[0094] Comparative Example 4

[0095] In Examples 1 to 4, we optimized the EpBN1.0-coated steel products and placed them on a self-developed loading device, subjecting them to a tensile stress of 60% of their yield strength. The test process, duration, and stress conditions (60% of their yield strength) were identical to those in Comparative Example 2.

[0096] Figure 3These are the strength test results of the functionalized boron nitride-epoxy composite anti-corrosion materials prepared in Examples 1-4 of the present invention. As can be seen from the figure, the ultimate tensile stress of the functionalized boron nitride-epoxy composite coating is significantly increased compared to the epoxy resin coating. Specifically, the coating in Example 1 exhibits the highest tensile strength, increasing its tensile strength by 21% compared to the pure epoxy resin coating.

[0097] The selection of the coated steel product EpBN1.0 in Comparative Examples 3 and 4 is based on the fact that the functionalized boron nitride surface micromorphology agglomeration phenomenon is best improved (see Figure 2 ) and the highest mechanical strength test results of composite coating materials (see Figure 3 ).

[0098] In order to verify the effect of the metal anticorrosion coating and preparation method for use in a load-coupled corrosion environment of the present invention, the following test was conducted, and the process is as follows:

[0099] 1) Scanning electron microscopy characterization of functionalized boron nitride nanomaterials of Examples 1 to 4 and boron nitride before functionalization

[0100] Figure 2 The surface micromorphology of the functionalized boron nitride nanomaterials in Examples 1 to 4 and their pre-functionalized counterparts is shown. The boron nitride surface is extremely smooth, exhibiting a layered molecular arrangement. Notably, the crystal growth direction exhibits no fixed derivative trend, indicating a relatively random growth process. Furthermore, the pre-functionalized boron nitride exhibits significant agglomeration, further confirming its typical two-dimensional structural characteristics. Compared to the pre-functionalized boron nitride sample, the agglomeration in Example 1 is significantly reduced, resulting in a more transparent and clear surface. Furthermore, a small amount of nanosheet structures appears. This improvement is attributed to the binding of dopamine molecules to the boron nitride sheet structure through π-π bonds, enabling stable dispersion of the boron nitride in the ethanol solution. The figure also shows that dopamine molecules have been successfully grafted onto the h-BN surface. Despite an increase in the boron nitride mass fraction, the effect remains superior to that of the pre-functionalized boron nitride sample, indicating that dopamine grafting has effectively improved the layered stacking of boron nitride to a certain extent.

[0101] 2) Coating mechanical properties test

[0102] The coating of the present invention was prepared on a Teflon mold using the coating process of Examples 1-4 and Comparative Example 1. The specimens for the tensile test were dumbbell-shaped, and their surfaces were sanded and polished with a grinder to ensure a flat and smooth surface. Each experimental group contained three replicates, for a total of 15 specimens. The tensile test was conducted on a universal testing machine at a loading rate of 1 mm / min in accordance with standard GB / T1040. When the coating broke, its maximum tensile strength was recorded. A higher tensile strength value indicates better mechanical properties of the coating.

[0103] Mechanical properties test data results are as follows Figure 3 As shown in Figure 1, the ultimate tensile stress of the functionalized boron nitride-epoxy composite coating is significantly higher than that of the epoxy resin coating. As the dopamine content in the functionalized boron nitride increases, the tensile strength of the coating also increases. Specifically, the coating in Example 1 exhibits the highest tensile strength, increasing by 21% compared to the pure epoxy resin coating.

[0104] 3) Corrosion resistance test of coated steel products under the coupling of load and corrosion environment

[0105] Four test groups (Comparative Examples 1, 2 and Comparative Examples 3, 4) were selected, with no less than three identical specimens in each group for repeated testing to ensure the reliability of the results. A resistance strain gauge was affixed to each specimen. At the beginning of the test, the steel sheet was placed on a customized loading device, and a load was applied to the coated steel product by applying force to the bolt specimen. The resistance strain gauge was connected to a strain gauge to measure the strain change of the specimen. By controlling the degree of strain, the corresponding load value was applied.

[0106] Depend on Figure 4 It can be seen that the corrosion resistance of Comparative Example 3 is better than that of Comparative Example 1. Under the condition of no chloride ion immersion, both Comparative Example 3 and Comparative Example 1 maintain a high level, higher than 10 9 order of magnitude, but for Example 3, |Z| 0.01Hz is always higher than that of Comparative Example 1. Under chloride ion immersion conditions, Comparative Example 3 |Z| 0.01Hz Still keep at 10 9 orders of magnitude and is basically stable, while in comparative example 1, after being soaked in chloride ions, |Z| 0.01Hz Down to 10 9 The value of boron nitride is below the order of magnitude and shows a downward trend. This is attributed to the fact that the lamellar structure of functionalized boron nitride can form a barrier layer in the coating, effectively hindering the penetration of corrosive media (water, oxygen, chloride ions, etc.), and giving full play to its physical isolation effect. Moreover, the uniform dispersion of functionalized boron nitride in the coating can significantly extend the diffusion path of the corrosive medium. In addition, due to its unique insulating properties, boron nitride avoids direct contact with the metal substrate and shields galvanic corrosion. Summary Adding modified boron nitride to epoxy coatings under no load can significantly improve their anti-corrosion properties and extend the durability of the coating.

[0107] Depend on Figure 4 It can be seen that under stress, the corrosion resistance of Comparative Example 4 is significantly better than that of Comparative Example 2. Under 60% yield tensile stress, during the period of no chloride ion immersion, |Z| 0.01Hz In 10 9 fluctuates around the order of magnitude; during chloride ion immersion, |Z| 0.01Hz Still above 10 8orders of magnitude. Under the action of applied tensile stress (60% yield strength), although the impedance of the coating in the present application decreased to a certain extent due to the combined action of applied load and corrosion environment, the value was still higher than 10 8 Ω·cm 2 , meeting the requirements of corrosion protection performance of the anticorrosive coating. In contrast, the |Z| 0.01Hz of Comparative Example 2 was always lower than that of Comparative Example 4, and after 14 days of immersion in the chloride ion, the |Z| 0.01Hz further decreased to 10 8 orders of magnitude. When the coated steel product is subjected to a certain tensile stress, both the epoxy resin coating and the dopamine-functionalized boron nitride coating will deteriorate. However, the coating in the present application exhibits more significant corrosion protection effect and can more effectively resist the deterioration of the coating under the stress and load coupling corrosion environment.

[0108] The content of the embodiments of the present specification is only a list of implementation forms of the inventive concept, and is only for the purpose of illustration. The protection scope of the present application should not be regarded as being limited to the specific forms stated in the present embodiments, and the protection scope of the present application also extends to equivalent technical means that can be thought of by those skilled in the art according to the inventive concept.

Claims

1. A functionalized boron nitride epoxy composite anti-corrosion coating for load-coupled corrosion environment, characterized in that: The functionalized boron nitride-epoxy composite anti-corrosion coating comprises functionalized boron nitride and epoxy resin. The functionalized boron nitride is modified by dopamine to obtain a dopamine-functionalized boron nitride nanomaterial. The modification is carried out by mixing the dopamine and boron nitride in an ethanol solution using an oxidation method and a nucleophilic reaction method. The dopamine-functionalized boron nitride nanomaterial is uniformly dispersed in the epoxy resin to form a dense structure.

2. The functionalized boron nitride epoxy composite anti-corrosion coating for load-coupled corrosion environment according to claim 1, characterized in that: In the functionalized boron nitride nanomaterial, dopamine serves as a modifier and boron nitride serves as a modified substance. The functionalized boron nitride is a two-dimensional nanomaterial formed by dopamine polymerization and grafting onto the surface of boron nitride.

3. The functionalized boron nitride epoxy composite anti-corrosion coating for load-coupled corrosion environment according to claim 2, characterized in that: The modification method is non-covalent bond modification, that is, the boron nitride surface is functionalized through the van der Waals force, hydrogen bond and π-π bond of dopamine.

4. The functionalized boron nitride epoxy composite anti-corrosion coating for load-coupled corrosion environment according to any one of claims 1 to 3, characterized in that: The preparation process of the dopamine functionalized boron nitride nanomaterial is as follows: First, boron nitride powder is added to a sodium hydroxide solution, stirred for reaction, and filtered, washed, and dried to obtain hydroxylated boron nitride powder; Secondly, dopamine and hydroxylated boron nitride powder are uniformly dispersed in tris(hydroxymethylaminomethane) hydrochloric acid buffer with a pH value of 8 to 8.5 through thermal oxidation reaction and nucleophilic reaction and are fully mixed. The boron nitride is functionalized by ultrasonic dispersion for 2 to 3 hours and heating with magnetic stirring in a water bath for full reaction. Polydopamine-modified boron nitride nanosheets are obtained by filtration, washing and drying.

5. The functionalized boron nitride epoxy composite anti-corrosion coating for load-coupled corrosion environment according to claim 4, characterized in that: The particle size of the boron nitride powder is 0.1-0.4 μm.

6. The functionalized boron nitride epoxy composite anti-corrosion coating for load-coupled corrosion environment according to claim 4, characterized in that: The mass ratio of the dopamine to the hydroxylated boron nitride is 1:1 to 1:2.

5.

7. A method for preparing a functionalized boron nitride epoxy composite anti-corrosion coating for load-coupled corrosion environment according to claim 1, characterized in that: The preparation method comprises the following steps: 1) Grinding: Weigh the functionalized boron nitride powder and grind it into powder; 2) Preparing a mixture: adding functionalized boron nitride to an anhydrous ethanol solution, ultrasonically dispersing for 2-3 hours in an ultrasonic disperser to obtain a boron nitride dispersion, adding epoxy resin to the dispersion and ultrasonicating again for 20-30 minutes; 3) Water bath thermal reaction: The mixed solution obtained in step 2) is subjected to rotary evaporation of ethanol at a temperature of 60 to 70 degrees Celsius under a vacuum environment to obtain an epoxy mixed solution; 4) Vacuum curing: reacting the epoxy mixture obtained in step 3) with a curing agent under vacuum pressure of 60 to 70 degrees Celsius for 30 to 60 minutes to remove bubbles and obtain an epoxy resin coating, i.e., a functionalized boron nitride epoxy composite anti-corrosion coating.

8. The preparation method according to claim 7, wherein In the functionalized boron nitride epoxy composite anti-corrosion coating, the mass ratio of each component is:

9. The preparation method according to claim 7, wherein The method further comprises the following steps: 5) Metal substrate pretreatment: Prepare a metal substrate with a size of (1-5) x (1-15) cm 2 The steel sheet was polished on 100-2000 grit sandpaper and then ultrasonically cleaned in ethanol and acetone solution for 20-30 minutes, and finally the liquid on the surface of the steel sheet was blown dry with nitrogen; 6) coating: coating the coating obtained in step 4) on the metal substrate; 7) Curing: The applied coating is cured at room temperature for 18 to 24 hours and then at 50 to 60 degrees Celsius for 2 to 4 hours to obtain a metal anti-corrosion coating and a metal product with the metal anti-corrosion coating.

10. An application of the functionalized boron nitride epoxy composite anti-corrosion coating for load-coupled corrosion environment as claimed in claim 1, which is used for civil buildings, pipelines, new energy power generation, offshore wind power or marine oil platforms under the coupling of load and corrosion environment.

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