A nitrogen-containing heterocyclic structure embedded intrinsic corrosion-resistant epoxy resin coating and a preparation method thereof

Abstract

The application discloses a nitrogen-containing heterocyclic structure embedded intrinsic corrosion-resistant epoxy resin coating and a preparation method thereof, and mainly relates to the field of high polymer materials. The coating comprises an epoxy resin and a nitrogen-containing heterocyclic structure chain extender, the epoxy resin coating is formed by the reaction of the epoxy resin and the nitrogen-containing heterocyclic structure chain extender, the nitrogen-containing heterocyclic structure is embedded in the crosslinking network of the epoxy resin through a covalent bond, and the nitrogen-containing heterocyclic structure chain extender is selected from one or more of triazole compounds, thiadiazole compounds, indole structure-containing compounds or 8-hydroxyquinoline structure-containing compounds. In the application, the nitrogen atom, the oxygen atom and the conjugated electron structure in the nitrogen-containing heterocyclic structure can form a stable coordination layer with a metal surface, so that the corrosion resistance of the metal matrix is improved; and since the nitrogen-containing heterocyclic structure participates in the construction of the crosslinking network of the epoxy resin, the problems of easy migration and easy loss of the traditional additive corrosion inhibitor can be avoided. The application is suitable for long-term corrosion protection of metal materials such as steel.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, specifically to a nitrogen-containing heterocyclic embedded intrinsic corrosion-resistant epoxy resin coating and its preparation method. Background Technology

[0002] Epoxy resin coatings are widely used in metal protection due to their excellent adhesion and chemical stability. However, microscopic defects inevitably arise during the curing and cross-linking process of epoxy resin. Furthermore, during long-term service, the coating is prone to microcracks and porosity due to mechanical stress, thermal stress, or UV aging. These defects provide penetration channels for corrosive media (such as water molecules, chloride ions, and oxygen molecules). Once these media penetrate along the defects to the metal substrate surface, they trigger localized corrosion reactions, leading to coating peeling and failure, and shortening the protective lifespan.

[0003] To improve the corrosion resistance of epoxy resin coatings, existing technologies typically employ physical blending to dope exogenous small-molecule corrosion inhibitors (such as nitrogen-containing heterocyclic compounds) into the resin matrix. These inhibitor molecules are physically dispersed within the polymer matrix, binding to the polymer primarily through non-covalent interactions such as hydrogen bonds and van der Waals forces. However, under long-term use or harsh environmental conditions (such as high temperature, high humidity, and salt spray environments), these non-covalent interactions are insufficient to effectively constrain the diffusion behavior of the inhibitor molecules. The inhibitor is prone to phase separation, internal migration, and even seepage and loss into the external environment. This not only leads to a significant decrease in the protective performance of the coating in the later stages, making long-term stable protection difficult, but also poses a potential pollution risk to the surrounding environment due to the migrating and loss of the inhibitor.

[0004] For example, Chinese patent CN202610381428.8 discloses a composite anti-corrosion coating based on modified polyaniline and its preparation and application methods. This method involves preparing a functional filler containing benzotriazole and introducing it into the coating system. However, the corrosion inhibitor contained in the functional filler in this method still exists in a physically loaded manner, and there is a lack of stable chemical bonding between the corrosion inhibitor and the substrate. Under long-term use or harsh environmental conditions, there is still a risk of corrosion inhibitor leakage and filler agglomeration that is difficult to completely avoid.

[0005] In recent years, to address the problem of corrosion inhibitor leaching, some existing technologies have attempted to introduce nitrogen-containing heterocyclic structures into epoxy resin systems via chemical bonds. For example, Chinese patent CN10308727A discloses an acrylate-grafted epoxy resin containing a triazole structure, where the triazole structure is attached to the epoxy resin molecular chain as a side group through a graft copolymerization reaction; Chinese patent CN115286767B discloses an antibacterial fluorinated modified epoxy vinyl ester resin, in which indole compounds participate in the reaction as one of the copolymerization raw materials. However, the above-mentioned existing technologies still have the following shortcomings: (1) Limitations of grafting structure: Grafting reaction is to attach nitrogen-containing heterocyclic structure to epoxy resin molecular chain in the form of side group. During long-term service, the grafted side chain may still face the risk of nitrogen-containing heterocyclic structure detachment due to chemical degradation factors such as ester hydrolysis. Its fixation and long-term stability in resin network still need to be further improved.

[0006] (2) Different functional focus: The above technical solutions mainly focus on antibacterial, sterilization or antifouling functions, and do not pay enough attention to or utilize the anti-corrosion function of nitrogen-containing heterocyclic structures coordinating to form films on metal surfaces.

[0007] (3) Differences in structural design: The above technologies do not embed nitrogen-containing heterocyclic structures as chain extenders into the epoxy resin backbone. Nitrogen-containing heterocyclic structures are not part of the backbone of the epoxy resin crosslinking network. Their fixation in the resin network depends on side group connections or copolymerization introduction. Compared with the backbone embedding method, there are still essential differences in terms of migration resistance and long-term stability.

[0008] Therefore, there is an urgent need in the existing technology to develop an epoxy resin material that can embed nitrogen-containing heterocyclic structures with metal coordination activity as chain extenders into the epoxy resin backbone, so that the anti-corrosion function comes from the material structure itself, and achieve long-term stable anti-corrosion without relying on the physical release of corrosion inhibitors. Summary of the Invention

[0009] The purpose of this invention is to provide a nitrogen-containing heterocyclic embedded intrinsically corrosion-resistant epoxy resin coating and its preparation method, which solves the problems of easy migration and loss of additive corrosion inhibitors and the difficulty in maintaining long-term stable corrosion resistance in existing technologies. By introducing a nitrogen-containing heterocyclic structure with metal coordination ability as a chain extender into the epoxy resin crosslinking network, the corrosion resistance function originates from the material structure itself, thereby achieving long-term stable intrinsic corrosion resistance.

[0010] To achieve the above objectives, the present invention employs the following technical solution: A nitrogen-containing heterocyclic structure embedded intrinsic corrosion-resistant epoxy resin coating includes epoxy resin and a nitrogen-containing heterocyclic chain extender. The epoxy resin coating is formed by reacting epoxy resin and nitrogen-containing heterocyclic chain extender. The nitrogen-containing heterocyclic structure is embedded in the epoxy resin crosslinking network through covalent bonds. The nitrogen-containing heterocyclic chain extender is selected from one or more of triazole compounds, thiadiazole compounds, compounds containing indole structures, or compounds containing 8-hydroxyquinoline structures.

[0011] Furthermore, the triazole compound is 3-amino-1,2,4-triazole or 3,5-diamino-1,2,4-triazole.

[0012] Furthermore, the thiadiazole compound is 2-amino-1,3,4-thiadiazole or 2,5-diamino-1,3,4-thiadiazole.

[0013] Furthermore, the compound containing the indole structure is tryptamine or a derivative thereof.

[0014] Furthermore, the compound containing the 8-hydroxyquinoline structure is 5-amino-8-hydroxyquinoline or a derivative thereof.

[0015] Furthermore, the epoxy resin is one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, or bisphenol S type epoxy resin.

[0016] Furthermore, the epoxy resin coating also includes a curing agent selected from one or more of 4,4′-diaminodiphenyl disulfide, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, or polyetheramine D230.

[0017] Furthermore, this includes the following steps: S1. Preheat the epoxy resin; S2. Add a nitrogen-containing heterocyclic chain extender to the preheated epoxy resin and stir the reaction under heating and vacuum conditions so that the chain extender reacts with the epoxy resin. S3. Add the curing agent and mix thoroughly; S4. Coat the resulting mixture onto the surface of a metal substrate; S5. Perform stepwise heating and curing to obtain a nitrogen-containing heterocyclic embedded intrinsic corrosion-resistant epoxy resin coating.

[0018] Furthermore, the heating reaction temperature in step S2 is 40–90°C, and the stirring time is 10–60 min; the metal substrate in step S4 is a carbon steel substrate; the stepwise heating and curing in step S5 includes: curing at 60–80°C for 1–2 h, curing at 100–120°C for 1–2 h, and curing at 130–150°C for 1–5 h.

[0019] A metal protective coating, comprising the aforementioned nitrogen-containing heterocyclic embedded intrinsic corrosion-resistant epoxy resin coating.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention utilizes nitrogen-containing heterocyclic structures as chain extenders in the chain extension reaction of epoxy resins, allowing these structures to be covalently embedded in the epoxy resin backbone, becoming part of the crosslinked network framework. In contrast, existing grafting modification techniques only connect nitrogen-containing heterocyclic structures to the molecular chain as side groups. There is a fundamental difference between backbone embedding and side group grafting at the molecular structure level.

[0021] 2. In this invention, the nitrogen-containing heterocyclic structure is part of the main chain skeleton, and there is no risk of hydrolysis and detachment. This fundamentally solves the problem of nitrogen-containing heterocyclic structure detaching from the resin network due to ester hydrolysis and other reasons in grafting modification technology, thereby achieving truly long-term stable intrinsic corrosion resistance.

[0022] 3. The nitrogen atoms, oxygen atoms, and conjugated electron structures in nitrogen-containing heterocyclic structures can form a stable coordination layer with the metal surface, improving the corrosion resistance of the metal matrix. Since the nitrogen-containing heterocyclic structure is fixed in the epoxy resin network by embedding in the main chain, its corrosion resistance comes from the material structure itself, rather than from the migration or release of corrosion inhibitors.

[0023] 4. The nitrogen-containing heterocyclic structure is embedded in the epoxy resin crosslinking network through covalent bonds, which can completely avoid the problems of easy agglomeration, easy migration and easy loss of traditional physical blending additive corrosion inhibitors.

[0024] 5. This method has a simple process, does not require complex graft copolymerization reaction conditions and organic solvents, is suitable for long-term corrosion protection of metal materials such as steel, and can flexibly control the anti-corrosion performance by adjusting the type and amount of chain extender. Attached Figure Description

[0025] Appendix Figure 1 This is a schematic diagram of the anti-corrosion epoxy coating of the present invention.

[0026] Appendix Figure 2 This is the infrared spectrum of the anti-corrosion epoxy coating of the present invention.

[0027] Appendix Figure 3 This is a Bode diagram of the anti-corrosion epoxy resin coating containing different mass fractions (3wt% and 7wt%) of the present invention after immersion in a 3.5wt% NaCl solution for 30 days. Detailed Implementation

[0028] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined in this application.

[0029] This invention relates to a nitrogen-containing heterocyclic embedded intrinsic corrosion-resistant epoxy resin coating and its preparation method, the main structure comprising: A nitrogen-containing heterocyclic structure embedded intrinsic corrosion-resistant epoxy resin coating includes epoxy resin and a nitrogen-containing heterocyclic chain extender. The epoxy resin coating is formed by reacting epoxy resin and nitrogen-containing heterocyclic chain extender. The nitrogen-containing heterocyclic structure is embedded in the epoxy resin crosslinking network through covalent bonds. The nitrogen-containing heterocyclic chain extender is selected from one or more of triazole compounds, thiadiazole compounds, compounds containing indole structures, or compounds containing 8-hydroxyquinoline structures.

[0030] The nitrogen atoms, oxygen atoms, or conjugated electron structures in the nitrogen-containing heterocyclic structure can coordinate with the metal surface. Furthermore, the nitrogen-containing heterocyclic chain extender can participate in the epoxy resin chain extension reaction and be fixed within the epoxy resin network structure.

[0031] Preferably, the triazole compound is 3-amino-1,2,4-triazole or 3,5-diamino-1,2,4-triazole.

[0032] Preferably, the thiadiazole compound is 2-amino-1,3,4-thiadiazole or 2,5-diamino-1,3,4-thiadiazole.

[0033] Preferably, the compound containing an indole structure is tryptamine or a derivative thereof.

[0034] Preferably, the compound containing the 8-hydroxyquinoline structure is 5-amino-8-hydroxyquinoline or a derivative thereof.

[0035] Preferably, the epoxy resin is one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, or bisphenol S type epoxy resin.

[0036] Preferably, the amount of the nitrogen-containing heterocyclic chain extender added is 1 to 15 wt% of the epoxy resin.

[0037] Preferably, the epoxy resin coating further includes a curing agent selected from one or more of 4,4′-diaminodiphenyl disulfide, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, or polyetheramine D230.

[0038] A method for preparing a nitrogen-containing heterocyclic embedded intrinsic corrosion-resistant epoxy resin coating includes the following steps: S1. Preheat the epoxy resin in a 60 ℃ oven to reduce the viscosity of the system and improve the dispersion uniformity of the chain extender in the epoxy resin. Then, take 10 parts of the preheated epoxy resin and add them to a three-necked flask for later use. S2. 3-Amino-1,2,4-triazole (ATA), 3,5-diamino-1,2,4-triazole (DATA), 2-amino-1,3,4-thiadiazole (ATD), 2,5-diamino-1,3,4-thiadiazole (DATD), tryptophan (TRY), and 5-amino-8-hydroxyquinoline (AHQ) were added to the epoxy resin system as nitrogen-containing heterocyclic chain extenders. The chain extenders were added to epoxy resin E-51 at different mass fractions, and the mixture was continuously stirred at 200-400 rpm for 30-60 min in a vacuum environment under a 60 ℃ water bath to ensure thorough dispersion of the chain extenders and their chain extension reaction with the epoxy resin, while simultaneously removing air bubbles from the system. S3. After the chain extension reaction is completed, use 4,4'-diaminodiphenyl disulfide (AFD), diethylenetriamine, triethylenetetramine, tetraethylenepentamine and polyetheramine D230 as curing agents respectively, and continue to stir under vacuum for 20-50 min to ensure that the curing agents and epoxy resin system are fully and evenly mixed. S4. Slowly coat the obtained uniformly mixed composite system onto the surface of a preheated Q235 steel sheet, wherein the Q235 steel sheet has a size of 10 cm × 10 cm. Preferably, the thickness of the prepared coating is 100-200 μm; S5. The coated sample is then subjected to stepwise temperature-curing: 60-80 ℃ for 1-2 h; 100-120 ℃ for 1-2 h; 130-150 ℃ for 1-5 h; finally, an epoxy resin composite coating with intrinsic corrosion resistance is obtained. Depending on the type of chain extender used, the resulting epoxy resin composite coating is named as follows: EP-ATA: An epoxy coating prepared using 3-amino-1,2,4-triazole as a chain extender; EP-DATA: An epoxy coating prepared using 3,5-amino-1,2,4-triazole as a chain extender; EP-ATD: An epoxy coating prepared using 2-amino-1,3,4-thiadiazole as a chain extender; EP-DATD: An epoxy coating prepared using 2,5-diamino-1,3,4-thiadiazole as a chain extender; EP-TRY: An epoxy coating prepared using tryptophan as a chain extender; EP-AHQ: An epoxy coating prepared using 5-amino-8-hydroxyquinoline as a chain extender.

[0039] Furthermore, the amount of the nitrogen-containing heterocyclic chain extender added is 1-30 wt% of the epoxy resin mass, preferably 1-15 wt%.

[0040] Furthermore, the amount of curing agent added is 1-30 wt% of the epoxy resin mass.

[0041] A protective coating for metals includes a nitrogen-containing heterocyclic embedded intrinsically corrosion-resistant epoxy resin coating. The coating possesses intrinsic corrosion resistance, and this corrosion resistance originates from the polymer structure itself, rather than from the release of corrosion inhibitors.

[0042] Example 1: Ten parts of bisphenol A type epoxy resin E-51 were taken and preheated at 40 °C for 30 min. 5 wt% of 3-amino-1,2,4-triazole was added, and the mixture was stirred at 200 rpm for 40 min under a 60 °C water bath and vacuum conditions to ensure the chain extender reacted fully with the epoxy resin. Then, 2.43 parts of curing agent 4,4′-diaminodiphenyl disulfide were added, and the mixture was stirred under vacuum for 20 min. The resulting mixture was uniformly coated onto the surface of a preheated Q235 steel sheet and cured sequentially at 80 °C for 2 h, 120 °C for 2 h, and 150 °C for 5 h to obtain an intrinsically corrosion-resistant epoxy coating.

[0043] Example 2: Take 20 parts of bisphenol F type epoxy resin F-51 and preheat it at 50 °C for 40 min. Add 7 wt% tryptamine to it and stir at 300 rpm for 50 min under a 70 °C water bath and vacuum conditions to allow the chain extender to fully react with the epoxy resin. Then add 4.86 parts of D230 curing agent at a 1:1 ratio of remaining epoxy groups to active hydrogen equivalents, and stir under vacuum for 30 min. The resulting mixture is uniformly coated onto the surface of a preheated Q235 steel sheet and cured sequentially at 60 °C for 1 h, 110 °C for 2 h, and 140 °C for 5 h to obtain an intrinsically corrosion-resistant epoxy coating.

[0044] Example 3: 30 parts of bisphenol S type epoxy resin (BPSER) were preheated at 60 °C for 35 min. 15 wt% of 5-amino-8-hydroxyquinoline was added, and the mixture was stirred at 300 rpm for 50 min under a 70 °C water bath and vacuum conditions to ensure the chain extender reacted fully with the epoxy resin. Then, 1 part of tetraethylenepentamine curing agent was added at a 1:1 ratio of remaining epoxy groups to active hydrogen equivalents, and the mixture was stirred under vacuum for 40 min. The resulting mixture was uniformly coated onto the surface of a preheated Q235 steel sheet and cured sequentially at 80 °C for 2 h, 100 °C for 2 h, and 130 °C for 2 h to obtain an intrinsically corrosion-resistant epoxy coating.

[0045] Example 4: 15 parts of bisphenol A type epoxy resin E-44 were preheated at 40 °C for 20 min. 7 wt% of 2,5-diamino-1,3,4-thiadiazole was added, and the mixture was stirred at 200 rpm for 40 min under a 45 °C water bath and vacuum conditions to ensure the chain extender reacted fully with the epoxy resin. Subsequently, 0.49 parts of diethylenetriamine curing agent were added at a 1:1 ratio of remaining epoxy groups to active hydrogen equivalents, and the mixture was stirred under vacuum for 25 min. The resulting mixture was uniformly coated onto the surface of a preheated Q235 steel sheet and cured sequentially at 75 °C for 4 h and 110 °C for 4 h to obtain an intrinsically corrosion-resistant epoxy coating.

[0046] Example 5: 20 parts of bisphenol A type epoxy resin E-42 were preheated at 45 °C for 25 min. 6 wt% of 2-amino-1,3,4-thiadiazole was added, and the mixture was stirred at 200 rpm for 45 min under a 50 °C water bath and vacuum conditions to ensure the chain extender reacted fully with the epoxy resin. Subsequently, 0.96 parts of tetraethylenepentamine curing agent were added at a 1:1 ratio of remaining epoxy groups to active hydrogen equivalents, and stirred under vacuum for 15 min. The resulting mixture was uniformly coated onto the surface of a preheated Q235 steel sheet and cured sequentially at 80 °C for 1 h, 120 °C for 1.5 h, and 150 °C for 4.5 h to obtain an intrinsically corrosion-resistant epoxy coating.

[0047] Example 6: 25 parts of bisphenol F type epoxy resin F-51 were preheated at 55 °C for 30 min. 10 wt% of 5-amino-8-hydroxyquinoline was added, and the mixture was stirred at 300 rpm for 40 min under a 70 °C water bath and vacuum conditions to ensure the chain extender reacted fully with the epoxy resin. Then, 2.35 parts of triethylenetetramine curing agent were added at a 1:1 ratio of remaining epoxy groups to active hydrogen equivalents, and stirred under vacuum for 25 min. The resulting mixture was uniformly coated onto the surface of a preheated Q235 steel sheet and cured sequentially at 60 °C for 1.5 h, 115 °C for 1.5 h, and 130 °C for 3 h to obtain an intrinsically corrosion-resistant epoxy coating.

[0048] Example 7: 15 parts of bisphenol F type epoxy resin SMF-170 were preheated at 65 °C for 30 min. 3 wt% tryptamine was added, and the mixture was stirred at 250 rpm for 25 min under a 70 °C water bath and vacuum conditions to allow for chain extension reaction with the epoxy resin. Subsequently, 4.51 parts of D230 curing agent were added at a 1:1 ratio of remaining epoxy groups to active hydrogen equivalents, and stirring was continued for 20 min. The resulting system was uniformly coated onto the surface of a Q235 steel sheet and cured at 80 °C for 2 h, 110 °C for 2 h, and 140 °C for 4 h to obtain an intrinsically corrosion-resistant epoxy coating.

[0049] Example 8: 20 parts of bisphenol F type epoxy resin F-51 were preheated at 60 °C for 30 min. 7 wt% of 3-amino-1,2,4-triazole was added, and the mixture was stirred at 250 rpm for 40 min under a 70 °C water bath and vacuum conditions to allow for chain extension reaction with the epoxy resin. Subsequently, 4.27 parts of 4,4′-diaminodiphenyl disulfide curing agent were added at a 1:1 ratio of remaining epoxy groups to active hydrogen equivalents, and stirred under vacuum for 20 min. The resulting system was uniformly coated onto the surface of a preheated Q235 steel sheet and cured sequentially at 80 °C for 2 h, 120 °C for 2 h, and 150 °C for 5 h to obtain an intrinsically corrosion-resistant epoxy coating.

[0050] Example 9: 25 parts of bisphenol F type epoxy resin SMF-180 were preheated at 65 °C for 30 min. 5 wt% of 5-amino-8-hydroxyquinoline was added, and the mixture was stirred at 300 rpm for 45 min under a water bath and vacuum at 65 °C to allow for chain extension reaction with the epoxy resin. Subsequently, 7.15 parts of D230 curing agent were added at a 1:1 ratio of remaining epoxy groups to active hydrogen equivalents, and the mixture was stirred under vacuum for 25 min. The resulting system was uniformly coated onto the surface of a preheated Q235 steel sheet and cured sequentially at 60 °C for 2 h, 80 °C for 2 h, and 120 °C for 3 h to obtain an intrinsically corrosion-resistant epoxy coating.

[0051] Example 10: 30 parts of bisphenol S type epoxy resin (BPSER) were preheated at 70 °C for 35 min. 10 wt% tryptamine was added, and the mixture was stirred at 300 rpm for 50 min under a 70 °C water bath and vacuum conditions to allow for chain extension with the epoxy resin. Subsequently, 1.35 parts of triethylenetetramine curing agent were added at a 1:1 ratio of remaining epoxy groups to active hydrogen equivalents, and stirred under vacuum for 30 min. The resulting system was uniformly coated onto the surface of a preheated Q235 steel sheet and cured sequentially at 80 °C for 2 h, 115 °C for 2 h, and 130 °C for 4 h to obtain an intrinsically corrosion-resistant epoxy coating.

[0052] Example 11: 25 parts of bisphenol A type epoxy resin E-42 were preheated at 60 °C for 40 min. 3 wt% of 5-amino-8-hydroxyquinoline was added, and the mixture was stirred at 250 rpm for 45 min under a 75 °C water bath and vacuum conditions to allow for chain extension reaction with the epoxy resin. Subsequently, 5.94 parts of 4,4′-diaminodiphenyl disulfide curing agent were added at a 1:1 ratio of remaining epoxy groups to active hydrogen equivalents, and stirred under vacuum for 20 min. The resulting system was uniformly coated onto the surface of a preheated Q235 steel sheet and cured sequentially at 90 °C for 2 h, 110 °C for 2 h, and 120 °C for 4 h to obtain an intrinsically corrosion-resistant epoxy coating.

[0053] Example 12: 30 parts of bisphenol A type epoxy resin E-44 were preheated at 75 °C for 35 min. 5 wt% of 3-amino-1,2,4-triazole was added, and the mixture was stirred at 300 rpm for 50 min under vacuum conditions at 80 °C to allow for chain extension reaction with the epoxy resin. Subsequently, 1.99 parts of diethylenetriamine curing agent were added at a 1:1 ratio of remaining epoxy groups to active hydrogen equivalents, and the mixture was stirred under vacuum for 25 min. The resulting system was uniformly coated onto the surface of a preheated Q235 steel sheet and cured sequentially at 80 °C for 2 h, 120 °C for 2 h, and 130 °C for 4 h to obtain an intrinsically corrosion-resistant epoxy coating.

[0054] Comparative Example 1 It is basically the same as Example 1, except that no nitrogen-containing heterocyclic chain extender is added.

[0055] Structural characterization and performance testing To further illustrate the beneficial technical effects of the intrinsically anti-corrosion epoxy resin involved in the embodiments of this application, relevant performance tests were conducted on the intrinsically anti-corrosion epoxy resin coatings involved in Example 1 and Comparative Example 1. The test results are shown in the attached figures. The test method is as follows: The coatings prepared in the above examples and comparative examples were applied to the surface of a sample (steel plate) to obtain a coating with a thickness of 150 μm. The coatings were cured in an oven at 80 ℃ for 1-2 h, at 120 ℃ for 1-2 h, and at 150 ℃ for 4-5 h to obtain an intrinsically anti-corrosion epoxy coating. The performance of the coatings was then tested. (1) Structure of intrinsic corrosion-resistant epoxy resin Figure 2The infrared spectrum of the intrinsically corrosion-resistant epoxy resin prepared in this invention shows the stretching vibrations at 3360 cm⁻¹ originating from the hydroxyl (-OH) groups formed after epoxy ring opening and the secondary amine (-NH⁻) groups on ATA, and the stretching vibration at 1590 cm⁻¹ originating from the C=N bond on the triazole ring. Furthermore, the complete disappearance of the epoxy characteristic peaks upon the introduction of ATA indicates that ATA is covalently linked to the side groups of the epoxy molecular chain.

[0056] FTIR test results show that the nitrogen-containing heterocyclic structure has successfully participated in the epoxy resin crosslinking reaction and is fixed in the epoxy resin molecular structure by covalent bonds.

[0057] (2) Corrosion resistance of intrinsically corrosion-resistant epoxy resin The coating was immersed in a 3.5 wt% NaCl aqueous solution for 30 days. A steel sheet coated with an epoxy composite layer was used as the working electrode, a platinum sheet as the counter electrode, a saturated calomel electrode as the reference electrode, and the 3.5 wt% NaCl aqueous solution as the electrolyte. The electrolyte was then subjected to a 10-day incubation period. -2 -10 5 Electrochemical impedance spectroscopy (EIS) was used to test the electrochemical data of the coating after 30 days of immersion in salt water within the Hz frequency range.

[0058] Figure 3 Bode curves of the corrosion resistance of intrinsically corrosion-resistant epoxy resin coatings with different mass fractions (3 wt% and 7 wt%) prepared for this invention were obtained. The epoxy resin coating with 7 wt% ATA content showed excellent corrosion resistance, with a low-frequency impedance modulus of 10. 9 Ω•cm 2 .

[0059] The results show that the low-frequency impedance modulus of the epoxy coating is significantly improved after the introduction of a nitrogen-containing heterocyclic chain extender, indicating that the corrosion resistance of the material is significantly enhanced.

[0060] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A nitrogen-containing heterocyclic embedded intrinsic corrosion-resistant epoxy resin coating, characterized in that: The coating comprises epoxy resin and a nitrogen-containing heterocyclic chain extender, wherein the epoxy resin coating is formed by reacting epoxy resin and nitrogen-containing heterocyclic chain extender, and the nitrogen-containing heterocyclic structure is covalently embedded in the epoxy resin crosslinking network; The nitrogen-containing heterocyclic chain extender is selected from one or more of triazole compounds, thiadiazole compounds, compounds containing indole structures, or compounds containing 8-hydroxyquinoline structures.

2. The intrinsically corrosion-resistant epoxy resin coating with a nitrogen-containing heterocyclic embedded structure according to claim 1, characterized in that: The triazole compound is 3-amino-1,2,4-triazole or 3,5-diamino-1,2,4-triazole.

3. The intrinsically corrosion-resistant epoxy resin coating with a nitrogen-containing heterocyclic embedded structure according to claim 1, characterized in that: The thiadiazole compound is 2-amino-1,3,4-thiadiazole or 2,5-diamino-1,3,4-thiadiazole.

4. The intrinsically corrosion-resistant epoxy resin coating with a nitrogen-containing heterocyclic embedded structure according to claim 1, characterized in that: The compound containing an indole structure is tryptamine or its derivative.

5. The intrinsically corrosion-resistant epoxy resin coating with a nitrogen-containing heterocyclic embedded structure according to claim 1, characterized in that: The compound containing the 8-hydroxyquinoline structure is 5-amino-8-hydroxyquinoline or a derivative thereof.

6. The nitrogen-containing heterocyclic embedded intrinsic corrosion-resistant epoxy resin coating according to claim 1, characterized in that: The epoxy resin is one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, or bisphenol S type epoxy resin.

7. The intrinsically corrosion-resistant epoxy resin coating with a nitrogen-containing heterocyclic embedded structure according to claim 1, characterized in that: The epoxy resin coating also includes a curing agent selected from one or more of 4,4′-diaminodiphenyl disulfide, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, or polyetheramine D230.

8. A method for preparing a nitrogen-containing heterocyclic embedded intrinsic corrosion-resistant epoxy resin coating as described in any one of claims 1-7, characterized in that: Includes the following steps: S1. Preheat the epoxy resin; S2. Add a nitrogen-containing heterocyclic chain extender to the preheated epoxy resin and stir the reaction under heating and vacuum conditions so that the chain extender reacts with the epoxy resin. S3. Add the curing agent and mix thoroughly; S4. Coat the resulting mixture onto the surface of a metal substrate; S5. Perform stepwise heating and curing to obtain a nitrogen-containing heterocyclic embedded intrinsic corrosion-resistant epoxy resin coating.

9. The method for preparing a nitrogen-containing heterocyclic embedded intrinsic corrosion-resistant epoxy resin coating according to claim 8, characterized in that: The heating reaction temperature in step S2 is 40-90℃, and the stirring time is 10-60 min; the metal substrate in step S4 is a carbon steel substrate; the stepwise heating and curing in step S5 includes: curing at 60-80℃ for 1-2 h, curing at 100-120℃ for 1-2 h, and curing at 130-150℃ for 1-5 h.

10. A metal protective coating, characterized in that: Including the nitrogen-containing heterocyclic embedded intrinsic corrosion-resistant epoxy resin coating according to any one of claims 1-7.

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