Preparation method and application of self-repairing epoxy resin anti-corrosion coating with metal corrosion early warning function

Abstract

This invention discloses a method for preparing a self-healing epoxy resin anti-corrosion coating with metal corrosion early warning function. UiO-67, with its large pore size and specific surface area and good stability, is used as the indicator carrier. 8-hydroxyquinoline, with good chemical stability, unaffected by light quenching, and maintaining stable fluorescence performance over a wide pH range, is selected as the indicator. A physical loading strategy is employed to load 8-hydroxyquinoline onto the UiO-67 framework, which is then incorporated into epoxy resin and coated onto a substrate to form an anti-corrosion coating. This invention solves the problems of incompatibility and uneven distribution between the indicator and the coating matrix. UiO-67 will undergo structural collapse in response to pH changes in the corrosion micro-region, releasing 8-hydroxyquinoline. 8-hydroxyquinoline complexes with iron ions, emitting fluorescence for corrosion early warning. Simultaneously, the collapse of UiO-67 releases organic ligands and Zr ions, which can be adsorbed or act as effective corrosion inhibitors on the metal surface, protecting the metal surface from corrosion and improving the corrosion inhibition effect of the coating.

Description

Technical Field

[0001] This invention relates to the field of metal anti-corrosion coating materials, and in particular to a method for preparing and applying a self-healing epoxy resin anti-corrosion coating with metal corrosion early warning function. Background Technology

[0002] Metal materials play an indispensable role in manufacturing, but corrosion is an unavoidable problem. Corrosion protection has always been a key scientific research area for countries worldwide. One of the most common metal corrosion protection strategies in manufacturing is surface coating technology. Traditional coatings achieve corrosion protection by physically isolating the metal substrate, such as carbon steel, from the corrosive environment, offering only passive protection. However, coatings often develop micropores and cracks during the curing process due to incomplete curing, and during use, long-term exposure to corrosive environments or mechanical damage can cause cracks and scratches, leading to corrosion failure.

[0003] Self-healing anti-corrosion coatings are created by adding corrosion inhibitors to the coating. When the coating is damaged, it develops the ability to actively repair itself, thereby compensating for the defects of the anti-corrosion coating. However, directly adding corrosion inhibitors to the coating substrate can cause the inhibitors to agglomerate within the coating or interact with the coating substrate, compromising the coating's tightness. Therefore, researchers often choose micro- or nano-containers with good compatibility with the substrate to load the corrosion inhibitors, thereby enhancing the anti-corrosion performance of the coating.

[0004] Coating failure typically occurs slowly over time, but these changes are often difficult to detect with the naked eye. If effective measures are not taken promptly, it can affect production safety, causing serious accidents, environmental pollution, resource waste, and hindering the development of new technologies. Currently, several non-destructive testing techniques are used in metal corrosion detection, such as magnetic particle testing, ultrasonic testing, electrochemical corrosion detection, and thermal infrared testing. However, these methods primarily address cracks caused by corrosion on metal surfaces, and their operation is relatively cumbersome. Therefore, incorporating nanomaterials with controllable release of fluorescent indicators into the coating as a means of metal corrosion detection is more advantageous. The location and extent of corrosion can be determined by the color and intensity of the fluorescence, providing early warning signals in the initial stages of corrosion, facilitating timely and effective measures to reduce the damage caused by corrosion and effectively prevent severe corrosion.

[0005] Metal-organic frameworks (MOFs) are a class of coordination polymers with porous structures that have been widely synthesized in recent years and have found extensive applications in gas and energy storage, separation, sensing, and drug delivery. MOFs possess designable structures composed of metal ions and organic ligands, and their nanoscale pore size provides excellent loading capacity, which is crucial for their use as multifunctional carriers. Furthermore, many MOFs exhibit affinity with organic polymers, enabling them to form highly cross-linked composite coatings, further enhancing the corrosion resistance of these coatings.

[0006] Several studies have already explored metal corrosion early warning coating materials. For example, Chinese patent application number 202210233477.9 discloses a damage-sensing corrosion early warning smart coating material and its application. This invention synthesizes metal-organic framework materials with fluorescent effects: Zr-MOF (UiO-(OH)2@RhB), Tb-MOF (Tb-HPyIDC), and Zn-MOF (QDs / CDs@ZIF-8). Under a 365nm UV lamp, Zr-MOF produces yellow fluorescence upon contact with the ambient medium (water) and green fluorescence upon reaction with aluminum ions generated from aluminum alloy corrosion; Tb-MOF produces yellow fluorescence upon contact with the ambient medium (water) and green fluorescence upon reaction with iron ions generated from carbon steel corrosion; Zn-MOF produces orange fluorescence upon contact with the ambient medium (water) and purple fluorescence upon reaction with copper ions generated from copper corrosion.

[0007] Other studies involve metal corrosion protection and corrosion early warning coating materials. For example, Chinese patent application number 202110181793.1 discloses a method for preparing a metal-organic framework compound material. This invention synthesizes a metal-organic framework compound by mixing zinc nitrate, 2-methylimidazole, and the corrosion responder 8-hydroxyquinoline. This compound can effectively encapsulate and release the corrosion responder, enabling it to respond promptly to corrosion, thereby monitoring and early warning of coating corrosion, extending the service life of metal materials, and improving service safety. Chinese patent application number 201611152081.2 discloses a polymer coating material for detecting metal corrosion and its preparation method. This invention combines pH-responsive fluorescent molecules fluorescein isothiocyanate and H3PW... 12 O 40 The fluorescent material is loaded into silica nanofiber containers and then dispersed in epoxy resin to obtain an epoxy resin coating material for detecting metal surface corrosion. This method partially solves the problem of incompatibility between directly adding fluorescent materials to the coating and the coating itself. When corrosion occurs, the pH value of the corroded area will increase. The fluorescent molecules in the smart polymer coating material react rapidly under the alkaline high pH value, thus exhibiting strong fluorescence indication at the corrosion site.

[0008] The above-mentioned existing technologies have the following problems:

[0009] 1. Direct Incorporation Affects Overall Integrity. Directly incorporating indicator molecules into the coating utilizes their sensitivity to pH and temperature, or their ability to form complexes with metal ions, to monitor changes in color or fluorescence for corrosion early warning. However, directly adding the indicator to the coating significantly affects its uniform distribution and may lead to poor compatibility, compromising the coating's integrity and hydrophobicity. Some metal ion-sensitive indicators, when directly applied to the epoxy resin coating matrix, may prematurely react with the metal ions, emitting fluorescence or changing its color—a phenomenon known as premature fluorescence. This also occurs with some pH-sensitive indicators. Therefore, addressing the incompatibility between the indicator and the coating matrix, premature fluorescence, and controlling the indicator's activation mechanism are among the key technical problems this invention aims to solve.

[0010] 2. Insufficient loading. MOF materials have been proven in numerous studies to be effective carriers for corrosion inhibitors in coatings, exhibiting good anti-corrosion effects. Existing research mainly focuses on ZIF and UiO series MOFs. ZIFs possess good stability, are stable in aqueous solutions, and are resistant to high temperatures, thus finding wide application in corrosion protection. Among these, a few materials, such as ZIF-7, ZIF-8, and ZIF-67, are commonly used as carriers for loading corrosion inhibitors. Since the corrosion inhibitors and other guest molecules mainly enter the pores through physical adsorption, the interaction between ZIFs and corrosion inhibitors is relatively limited, resulting in a limitation to a few corrosion inhibitors such as BTA that can be loaded. Taking ZIF-8 as an example, its pore size and pore volume are 1.6 nm and 0.5 cm³, respectively. 3 / g, the UiO series, mainly represented by UiO-66, has larger pore size and pore volume than the ZIF series materials, at 2.4nm and 0.9cm, respectively. 3 MOFs (Metal-Oxide-Factory Materials) are a class of MOFs that are easily synthesized on a laboratory scale and possess excellent thermal, mechanical, water, and moisture stability. The relatively small pore size and volume of these materials limit the amount of corrosion inhibitor that can be loaded. Therefore, enhancing the interaction between MOFs and guest molecules, increasing the guest molecule loading rate, and controlling the release of guest molecules without environmental influence are other technical problems that this invention aims to solve. Summary of the Invention

[0011] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing a self-healing epoxy resin anti-corrosion coating with metal corrosion early warning function. This invention uses UiO-67, which has a larger pore size and specific surface area and better stability, as an indicator carrier. 8-Hydroxyquinoline, which has good chemical stability, is not easily affected by light quenching, and maintains stable fluorescence performance over a wide pH range, is selected as the indicator. A physical loading strategy is employed, loading 8-hydroxyquinoline onto the UiO-67 framework through mechanical stirring and incorporating it into the epoxy resin coating, thereby solving the problems of incompatibility and uneven distribution between the indicator and the coating matrix. UiO-67 will undergo structural collapse in response to changes in pH in the corrosion micro-region, releasing 8-hydroxyquinoline. 8-Hydroxyquinoline complexes with iron ions, emitting fluorescence for corrosion early warning. Simultaneously, after collapse, UiO-67 releases organic ligands and Zr ions, which can be adsorbed or act as effective corrosion inhibitors on the metal surface, protecting the metal surface from corrosion and further improving the corrosion inhibition effect of the coating.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0013] A method for preparing a self-healing epoxy resin anti-corrosion coating with metal corrosion early warning function includes the following steps:

[0014] (1) Synthesis of UiO-67: Zirconium chloride and benzoic acid were dissolved in N,N'-dimethylformamide (DMF) and sonicated for 10-20 min to dissolve completely. Then, 4,4'-biphenyl dicarboxylic acid was added to the solution and sonicated for 10-20 min to mix evenly. The resulting mixed solution was placed in a polytetrafluoroethylene reactor and reacted at 120-130℃ for 24-28 h. After cooling to room temperature, the precipitate was separated by centrifugation. The precipitate was suspended in 10 ml of DMF and allowed to stand at room temperature for 2-6 hours. The suspension was then centrifuged and decanted to remove the solvent. The solid was suspended in 10 ml of ethanol and allowed to stand at room temperature for 2-6 hours. The suspension was then centrifuged and decanted to remove the solvent. The resulting solid was dried in a vacuum drying oven at 65-75℃ for 12-14 h to obtain a white powder, i.e., UiO-67.

[0015] (2) Synthesis of 8-HQ-UiO-67: 8-hydroxyquinoline (8-HQ) was added to ethanol and ultrasonically dispersed for 10-20 min. UiO-67 was dissolved in the above ethanol solution and ultrasonically dispersed and mixed for 10-20 min. The mixture was then placed on a magnetic stirrer and stirred for 18-24 h. The mixture was centrifuged at 850-9000 rpm. The product was washed with excess ethanol and dried in a vacuum drying oven at 65-75℃ for 12-14 h to obtain a light yellow powder, namely 8-HQ-UiO-67.

[0016] (3) Preparation of epoxy resin coating containing 8-HQ-UiO-67: 8-HQ-UiO-67 was ultrasonically dispersed in epoxy resin, and the viscosity was adjusted by a mixed solution of n-butanol and xylene. After mechanical stirring for 30-40 min, a curing agent was added and mechanically stirred for 10-20 min to obtain a mixture. The mixture was then coated onto the pretreated substrate using a four-sided coating applicator and cured at room temperature for 48-55 h. After drying in an oven at 75-85℃ for 3.5-4.5 h, an epoxy resin composite coating containing 8-HQ-UiO-67 was obtained.

[0017] Further, in step (1), the ratio of zirconium chloride to benzoic acid, 4,4'-biphenyldicarboxylic acid, and DMF is 0.110~0.120g:0.610~0.620g, 0.110~0.120g:0.115~0.135g, and 0.110~0.120g:16~22ml, respectively.

[0018] Furthermore, in step (2), the ratio of 8-HQ to UiO-67 is 300~310mg:90-110mg.

[0019] Furthermore, in step (3), the amount of 8-HQ-UiO-67 used is 1-2% of the mass of the epoxy resin.

[0020] Further, in step (3), the amount of the mixed solution of n-butanol and xylene is 25-30% of the mass of epoxy resin.

[0021] Further, in step (3), the volume ratio V of the mixed solution of n-butanol and xylene is... 正丁醇 :V 二甲苯 = 3:7.

[0022] Further, in step (3), the curing agent is polyamide, and the amount of polyamide curing agent is 45-55% of the mass of epoxy resin.

[0023] Furthermore, in step (3), the substrate is Q235 carbon steel sheet, etc.

[0024] Furthermore, in step (3), the pretreatment method for Q235 carbon steel sheet is as follows: first, use 600-mesh, 1000-mesh, and 1500-mesh sandpaper to polish it smooth, then sonicate it in ethanol for 10-15 minutes and take it out to dry.

[0025] Furthermore, in step (3), the thickness of the epoxy resin composite coating containing 8-HQ-UiO-67 is 50±3μm.

[0026] The two technical solutions closest to this invention are as follows: 1. Chinese patent application number 201611152081.2 discloses a polymer coating material for detecting metal corrosion and its preparation method. Compared with this invention, the shortcomings of this invention are as follows: (1) The amount of fluorescent molecules used is reduced by using silica nanocontainers, which solves the compatibility problem to a certain extent, but its loading capacity is relatively low (only 8%). The indicator carrier UiO-67 of this invention can be uniformly distributed in the coating and has a large specific surface area, which can load more indicators (loading reaches 24%), thereby achieving the corrosion early warning effect. (2) Silica itself has certain acidity and alkalinity. When it encounters silicic acid corrosion inhibitors and corrosion inhibitors containing active groups such as hydroxyl and amine groups, it will react chemically with them, resulting in a decrease or disappearance of the slow release effect. The UiO-67 used in this invention has excellent thermal, mechanical, water and moisture stability, which can avoid the influence of other environmental factors. It can release the indicator after responding to the pH change of the corrosion micro-area after corrosion occurs, thereby achieving the corrosion early warning effect. 2. Chinese Patent Application No. 202110181793.1 discloses a method for preparing metal-organic framework compound materials. Compared with this invention, the shortcomings of this invention are as follows: (1) ZIF-8 loaded with 8-HQ was prepared by a one-step crystallization method at room temperature. During the synthesis process, the organic ligands compete with 8-HQ, resulting in a low loading amount of 8-HQ, with the highest loading amount being only 4.5%. This means that each unit weight of ZIF-8 can only carry a limited amount of 8-HQ. In this invention, UiO-67 is first synthesized by physical loading, and then 8-HQ is loaded onto UiO-67 by mechanical stirring. UiO-67 has a larger specific surface area, which greatly improves the loading amount of 8-HQ, with a loading amount as high as 24%. (2) The one-step crystallization method significantly affects the particle size of MOFs. Once the amount of 8-HQ increases, the particle size becomes very large, increasing from the initial 150nm to 900nm, resulting in poor compatibility with the coating and easy agglomeration in the coating, which damages the coating's compactness. In contrast, this invention first synthesizes UiO-67, and by changing the amount of regulator, the synthesized UiO-67 has a uniform size that is precisely controllable within 100nm-200nm, which can more effectively improve the integrity of the coating.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. This invention uses zirconium-based metal-organic framework UiO-67, synthesized with organic ligands having a double benzene ring structure, as an indicator carrier. It has a larger pore size and a larger specific surface area, thereby increasing the loading of the indicator and solving to some extent the problem of insufficient fluorescence caused by insufficient indicator loading.

[0029] 2. This invention employs a combined mechanical and chemical loading method to load 8-HQ, a fluorescent indicator, into UiO-67. Through hydrogen bonding, van der Waals forces, electrostatic forces, or Lewis acids, the 8-HQ is more stably loaded into UiO-67. Compared to other one-pot methods for MOFs, this better avoids premature loss of the fluorescent indicator due to environmental changes. Furthermore, it allows for controlled release of 8-HQ based on environmental changes, preventing widespread fluorescence response across the entire coating area and enabling targeted fluorescence response, thus facilitating earlier detection of defects at specific locations within the coating.

[0030] 3. The UiO-67 powder prepared by this invention can be synthesized into UiO-67 with various sizes and structures by adjusting the ratio of the regulator. When used in anti-corrosion coatings, the particle size can be precisely controlled within 100-200 nm. It has good compatibility with the coating substrate, can be uniformly dispersed in the coating substrate without agglomeration, and has a stable structure in acidic to weakly alkaline environments, making it easy to store. Attached Figure Description

[0031] Figure 1 XRD powder diffraction patterns of UiO-67 and UiO-67 loaded with 8-HQ.

[0032] Figure 2 This is a sustained-release curve of 8-HQ under alkaline conditions.

[0033] Figure 3 This is a scanning electron microscope image of UiO-67.

[0034] Figure 4 The electrochemical impedance spectroscopy of the sample surface after being immersed in sodium chloride solution for different times in Example 1 is shown.

[0035] Figure 5 The electrochemical impedance spectroscopy of the sample surface after being immersed in sodium chloride solution for different times in Example 2 is shown.

[0036] Figure 6 The results of the anti-corrosion coating with added 8-HQ-UiO-67 after immersion in 3.5% NaCl solution and exposure to natural light on day 1 (a) and day 14 (b).

[0037] Figure 7 The results of the anti-corrosion coating with 8-HQ-UiO-67 added after immersion in 3.5% NaCl solution and irradiation under 365nm UV lamp on day 1 (a) and day 14 (b). Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments and accompanying drawings, but the present invention is not limited thereto.

[0039] In the following examples, zirconium chloride (98% purity), 4,4'-biphenyldicarboxylic acid (98% purity), and benzoic acid (99% purity) were products of Adamas Reagent Co., Ltd. N,N'-dimethylformamide (DMF) and 8-hydroxyquinoline (8-HQ, 99% purity) were products of Aladdin Reagent Co., Ltd. Ethanol, n-butanol, xylene, etc., were products of Sinopharm Chemical Reagent Co., Ltd.

[0040] The pretreatment method for Q235 carbon steel sheets is as follows: First, use 600-grit, 1000-grit, and 1500-grit sandpaper to polish them smooth. Then, sonicate them in ethanol for 10 minutes and remove them to air dry for later use. Example 1

[0041] (1) Synthesis of UiO-67: 0.120 g of zirconium chloride and 0.628 g of benzoic acid were dissolved in 20 ml of DFM and sonicated for 10 min to dissolve completely. Then, 0.125 g of 4,4'-biphenyl dicarboxylic acid was added to the solution and sonicated for 10 min to mix completely. The resulting mixture was placed in a polytetrafluoroethylene reactor and reacted at 120 °C for 24 h. After cooling to room temperature, the precipitate was separated by centrifugation. The precipitate was suspended in 10 ml of DMF. After standing at room temperature for 2-6 hours, the suspension was centrifuged and decanted to remove the solvent. The solid was suspended in 10 ml of ethanol and stood at room temperature for 2-6 hours. After centrifugation and decanting, the suspension was removed. The resulting solid was dried in a vacuum drying oven at 70 °C for 12 h to obtain a white powder, i.e., UiO-67.

[0042] (2) Synthesis of 8-HQ-UiO-67: 600 mg of 8-HQ was added to 20 ml of ethanol and ultrasonically dispersed for 10 min. 200 mg of UiO-67 was dissolved in the above ethanol solution and ultrasonically dispersed and mixed for another 10 min. The mixture was then stirred on a magnetic stirrer for 24 h. The product was centrifuged at 8500 rpm, washed with excess ethanol, and dried in a vacuum drying oven at 70 °C for 12 h to obtain a light yellow powder, namely 8-HQ-UiO-67.

[0043] (3) Preparation of epoxy resin coating containing 8-HQ-UiO-67: 35 mg of 8-HQ-UiO-67 powder was ultrasonically dispersed in 1.75 g of epoxy resin, and a mixed solution of 0.52 g of n-butanol and xylene (V 正丁醇 :V 二甲苯= 3:7) Adjust the viscosity. After mechanical stirring for 30 min, add 0.875 g of polyamide curing agent and mechanically stir for 10 min to obtain a mixture. Then, use a four-sided coating applicator to coat the mixture onto the pretreated Q235 carbon steel sheet, cure at room temperature for 2 days, and then dry in an 80℃ oven for 4 h to successfully prepare an epoxy resin composite coating with a thickness of 50±3 μm containing 2.0% 8-HQ-UiO-67 (based on the mass of epoxy resin). Example 2

[0044] (1) Synthesis of UiO-67: 0.120 g of zirconium chloride and 1.256 g of benzoic acid were dissolved in 20 ml of DMF and sonicated for 10 min to dissolve completely. Then, 0.125 g of 4,4'-biphenyl dicarboxylic acid was added to the solution and sonicated for 10 min to mix completely. The resulting mixture was placed in a polytetrafluoroethylene reactor and reacted at 120 °C for 24 h. After cooling to room temperature, the precipitate was separated by centrifugation. The precipitate was suspended in 10 ml of DMF and allowed to stand at room temperature for 2-6 hours. The suspension was then centrifuged and decanted to remove the solvent. The solid was suspended in 10 ml of ethanol and allowed to stand at room temperature for 2-6 hours. The suspension was then centrifuged and decanted to remove the solvent. The solid was dried in a vacuum drying oven at 70 °C for 12 h to obtain a white powder, namely UiO-67.

[0045] (2) Synthesis of 8-HQ-UiO-67: 900 mg of 8-HQ was added to 30 ml of ethanol and ultrasonically dispersed for 10 min. 300 mg of UiO-67 was dissolved in the above ethanol solution and ultrasonically dispersed and mixed for another 10 min. The mixture was then stirred on a magnetic stirrer for 24 h. The product was centrifuged at 8500 rpm, washed with excess ethanol, and dried in a vacuum drying oven at 70 °C for 12 h to obtain a light yellow powder, namely 8-HQ-UiO-67.

[0046] (3) Preparation of epoxy resin coating containing 8-HQ-UiO-67: 17.5 mg of 8-HQ-UiO-67 powder was ultrasonically dispersed in 1.75 g of epoxy resin, and a mixed solution of 0.52 g of n-butanol and xylene (V 正丁醇 :V 二甲苯 = 3:7) Adjust the viscosity. After mechanical stirring for 30 min, add 0.875 g of polyamide curing agent and mechanically stir for 10 min to obtain a mixture. Then, use a four-sided coating applicator to coat the mixture onto a pretreated Q235 carbon steel sheet, cure at room temperature for 2 days, and then dry in an 80℃ oven for 4 h to successfully prepare an epoxy resin composite coating with a thickness of 50±3 μm containing 1.0% 8-HQ-UiO-67 (based on the mass of epoxy resin).

[0047] Figure 1The XRD powder diffraction pattern of UiO-67 in Example 2 shows that UiO-67 was successfully synthesized. The powder X-ray diffraction pattern of 8-HQ-UiO-67 shows that the main framework of UiO-67 was not destroyed after loading 8-HQ.

[0048] Figure 2 This is a sustained-release curve of 8-HQ under alkaline conditions in Example 2. It shows that when the UiO-67 framework is destroyed, the 8-HQ loaded therein can be released stably.

[0049] Figure 3 The image shown is a scanning electron microscope image of UiO-67 in Example 2. Its main morphology is an octahedral structure with uniform particle size and an average particle size of about 147 nm (obtained by ImageJ image analysis software).

[0050] Application Example 1

[0051] Using Q235 carbon steel sheet as the substrate, an epoxy resin coating without 8-HQ-UiO-67 was applied to a thickness of approximately 50 μm. The coating was cured at room temperature for 2 days, then dried in an oven at 80℃ for 4 hours. Afterward, the coating was immersed in a 3.5% NaCl solution, and electrochemical impedance spectroscopy (EIS) was collected for different immersion times. Figure 4 As shown.

[0052] Application Example 2

[0053] Using Q235 carbon steel sheet as the substrate, an epoxy resin coating with 2.0% 8-HQ-UiO-67 was applied to a thickness of approximately 50 μm. The coating was cured at room temperature for 2 days, then dried in an oven at 80℃ for 4 hours. Afterward, the coating was immersed in a 3.5% NaCl solution, and electrochemical impedance spectroscopy (EIS) was collected for different immersion times. Figure 5 As shown.

[0054] (1) Compare the electrochemical impedance spectra of the surfaces of the samples in Examples 1 and 2 after immersion in sodium chloride solution for different times. Figure 4 and Figure 5 The results showed that the electrochemical impedance value of the anti-corrosion coating with added 8-HQ-UiO-67 after immersion for 1 day was higher than that of the anti-corrosion coating without 8-HQ-UiO-67. Furthermore, after immersion for 7 and 14 days, the rate of decrease in the electrochemical impedance value of the anti-corrosion coating with added 8-HQ-UiO-67 was significantly lower than that of the anti-corrosion coating without 8-HQ-UiO-67. This indicates that the incorporation of 8-HQ-UiO-67 into epoxy resin can significantly improve its corrosion resistance to carbon steel sheets.

[0055] (2) After the anti-corrosion coating with added 8-HQ-UiO-67 was immersed in 3.5wt% NaCl solution for different times, the sample surface was irradiated with natural light and a 365nm wavelength ultraviolet lamp (see Figure 6 and Figure 7 Under natural light, there was no difference between day 1 and day 14. Under irradiation with a 365nm wavelength ultraviolet lamp, the coating surface emitted blue-green fluorescence on day 1, with no other colors of fluorescence. After immersion for 14 days, the coating was blue-green overall, but there were yellow fluorescent spots of different sizes, indicating that some areas of the coating had defects at this time, and corrosive media entered the interior of the coating. This caused the UiO-67 loaded with 8-HQ to collapse due to pH change, releasing the loaded 8-HQ, which chelated with ferrous ions and emitted yellow fluorescence.

Claims

1. A method for preparing a self-healing epoxy resin anti-corrosion coating with metal corrosion early warning function, characterized in that, Includes the following steps: (1) Synthesis of UiO-67; The ratios of zirconium chloride to benzoic acid, 4,4'-biphenyl dicarboxylic acid, and DMF in the raw materials for preparing UiO-67 are 0.110~0.120g : 0.610~0.620g, 0.110~0.120g : 0.115~0.135g, and 0.110~0.120g : 16~22ml, respectively. (2) Synthesis of 8-HQ-UiO-67: 8-HQ was added to ethanol and ultrasonically dispersed evenly. UiO-67 was dissolved in the above ethanol solution and ultrasonically dispersed and mixed evenly. The mixture was placed on a magnetic stirrer and stirred for 18-24h. Then it was centrifuged, the product was washed with excess ethanol, and the product was dried to obtain 8-HQ-UiO-67. The dosage ratio of 8-HQ to UiO-67 is 300~310mg:90~110mg; (3) Preparation of epoxy resin coating containing 8-HQ-UiO-67: 8-HQ-UiO-67 was ultrasonically dispersed in epoxy resin, and the viscosity was adjusted by a mixed solution of n-butanol and xylene. After stirring evenly, a curing agent was added and stirred evenly to obtain a mixture. Then, the mixture was coated onto the pretreated substrate using a four-sided coating applicator and cured at room temperature for 48-55 hours. After drying, an epoxy resin composite coating containing 8-HQ-UiO-67 was obtained.

2. The method for preparing a self-healing epoxy resin anti-corrosion coating with metal corrosion early warning function according to claim 1, characterized in that, In step (1), the synthesis method of UiO-67 is as follows: Zirconium chloride and benzoic acid are dissolved in DMF and sonicated to completely dissolve them. Then, 4,4'-biphenyl dicarboxylic acid is added to the solution and sonicated to mix evenly. The resulting mixed solution is placed in a polytetrafluoroethylene reactor and reacted at 120~130℃ for 24~28 h. After cooling to room temperature, the precipitate is separated by centrifugation. The precipitate is suspended in DMF and allowed to stand at room temperature for 2-6 hours. The suspension is centrifuged and decanted to remove the solvent. The solid is suspended in ethanol and allowed to stand at room temperature for 2-6 hours. The suspension is centrifuged and decanted to remove the solvent. The obtained solid is dried to obtain UiO-67.

3. The method for preparing a self-healing epoxy resin anti-corrosion coating with metal corrosion early warning function according to claim 1, characterized in that, In step (3), the amount of 8-HQ-UiO-67 used is 1 to 2% of the mass of epoxy resin.

4. The method for preparing a self-healing epoxy resin anti-corrosion coating with metal corrosion early warning function according to claim 1, characterized in that, In step (3), the amount of the mixed solution of n-butanol and xylene is 25-30% of the mass of the epoxy resin. In the mixed solution of n-butanol and xylene, the volume ratio V 正丁醇 :V 二甲苯 = 3:

7.

5. The method for preparing a self-healing epoxy resin anti-corrosion coating with metal corrosion early warning function according to claim 1, characterized in that, In step (3), the curing agent is polyamide, and the amount of polyamide curing agent is 45-55% of the mass of epoxy resin.

6. The method for preparing a self-healing epoxy resin anti-corrosion coating with metal corrosion early warning function according to claim 1, characterized in that, In step (3), the substrate is a Q235 carbon steel sheet. The pretreatment method of the Q235 carbon steel sheet is as follows: first, use 600-grit, 1000-grit, and 1500-grit sandpaper to polish it smooth, then sonicate it in ethanol for 10-15 minutes and take it out to dry.

7. The method for preparing a self-healing epoxy resin anti-corrosion coating with metal corrosion early warning function according to claim 1, characterized in that, In step (3), the thickness of the epoxy resin composite coating containing 8-HQ-UiO-67 is 50±3μm.

8. The application of the self-healing epoxy resin anti-corrosion coating obtained by the preparation method according to any one of claims 1 to 7 in metal corrosion early warning.

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