A carbon fiber reinforced resin-based composite coating and a method of making and using the same

Abstract

The application discloses a carbon fiber reinforced resin-based composite coating and a preparation method and application thereof, and belongs to the technical field of pipeline corrosion protection. The preparation method of the carbon fiber reinforced resin-based composite coating is as follows: pretreated carbon fibers are immersed into a curing agent to obtain a curing agent mixture impregnated with the carbon fibers; epoxy resin, asphalt, diamino diphenyl methane and glycidyl ether are mixed, and the mixture is mixed with the curing agent mixture impregnated with the carbon fibers to obtain a resin mixture; the resin mixture is coated on the surface of a pretreated substrate, and is cured at room temperature to obtain the carbon fiber reinforced resin-based composite coating. The carbon fiber reinforced resin-based composite coating prepared by the method has high curing speed and excellent corrosion resistance and toughness, and can be applied to rapid plugging of pipelines in harsh environments, thereby providing a thought for application of the carbon fiber reinforced resin-based composite coating in the field of oil and gas pipeline repair.

Description

Technical Field

[0001] This invention belongs to the field of pipeline corrosion protection technology, specifically relating to a carbon fiber reinforced resin-based composite coating, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] As pipelines age, some older pipelines experience corrosion, thinning, and even leaks, frequently requiring sealing operations. However, traditional pipeline maintenance methods often suffer from significant construction disruptions, long downtime, low efficiency, substantial safety hazards, and slow response times, failing to meet the urgent needs of modern oil and gas pipelines for rapid, efficient, and safe operation. Therefore, a new rapid pipeline sealing technology needs to be developed.

[0004] Rapid pipeline sealing technology enables quick and effective plugging of pipeline leaks without interrupting pipeline operation, significantly reducing maintenance time and improving efficiency. Currently, rapid pipeline sealing technology has developed into several mature methods and technical systems. Among these, techniques for external pipeline repair mainly include clamp sealing and adhesive sealing. Clamp sealing uses specially designed clamps that are fitted onto the pipeline and bolted together to effectively seal the pipe. This technique is suitable for smaller diameter pipelines, but clamps are prone to corrosion and secondary leaks in humid and hot environments. Adhesive sealing simply involves applying resin adhesive to the pipe cut or leak point and allowing it to cure naturally to form a strong sealing layer. This method is simple to operate and suitable for various pipe materials and sizes. However, traditional polymer resin adhesives still suffer from slow curing speeds, high brittleness after curing, poor corrosion resistance in harsh environments, and insufficient strength and toughness, limiting their application in the field of rapid pipeline sealing.

[0005] Fiber-based materials are widely used in polymer coatings due to their high strength, good flexibility and toughness, corrosion resistance, and diverse applications. Fiber-based materials (such as glass fiber and polyester fiber) can typically withstand high tensile and compressive forces, making them suitable for applications requiring high loads, such as pipe repair and reinforcement. Furthermore, fiber-based materials can be bent and twisted to a great extent without easily breaking, allowing for a tight fit when filling gaps or wrapping pipes, reducing the possibility of shrinkage deformation and cracking. Simultaneously, fiber-based materials also possess excellent corrosion resistance, resisting chemical attack and maintaining long-term stability and durability. Finally, fiber-based materials can exist in the form of fiber cloth, fiber tape, or fiber rope, facilitating construction and operation, and are easily combined with other materials (such as resin) to form composite materials, which facilitates the application of fiber-based composite materials in the field of rapid pipe sealing. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a carbon fiber reinforced resin-based composite coating, its preparation method, and its application. For a rapid-curing coating system, carbon fiber cloth (CFs) is introduced into an epoxy resin coating. The interfacial bonding between CFs and resin is investigated, as well as the filling of defects such as pores and cracks in the resin coating by CFs. The influence of CFs on the toughness, corrosion resistance, and bonding strength of the composite coating is analyzed, and its advantages in rapid pipeline sealing technology are elucidated.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] In a first aspect, the present invention provides a carbon fiber reinforced resin-based composite coating comprising the following components by weight: 0.5-2 parts carbon fiber, 3-5 parts curing agent, 8-12 parts epoxy resin, 1-1.5 parts asphalt, 1-2 parts diaminodiphenylmethane, and 1-2 parts glycidyl ether.

[0009] In one or more embodiments, the carbon fiber comprises carbon fiber cloth (CFs).

[0010] Carbon fiber can be used directly, or carbon fiber cloth can be used; however, carbon fiber cloth offers superior performance. In carbon fiber cloth, the vast majority of carbon fibers are arranged in parallel and are relatively tightly packed. The carbon fibers are of relatively uniform thickness, with a diameter between 4.5 μm and 4.8 μm. There are no specific limitations on the specific texture of the carbon fiber cloth; for example, plain weave cloth can be used in the embodiments.

[0011] In one or more embodiments, the curing agent is an amine curing agent, which includes polyetheramine curing agents and aliphatic amine curing agents, preferably polyetheramine curing agents. The polyetheramine curing agent is one or more of D230, D400, T403, D2000, and T5000, preferably polyetheramine D400 curing agent.

[0012] In one or more embodiments, the epoxy resin includes E51 resin and E44 resin, preferably E51 resin. Epoxy resin, through its polar groups such as hydroxyl and ether bonds, forms strong chemical bonds and physical anchoring with carbon fibers, ensuring high interfacial bonding strength. Furthermore, its high crosslinking density after curing imparts high modulus, creep resistance, and fatigue resistance to the coating. Its chemical inertness allows it to withstand acid, alkali, and oil / gas corrosive media and a wide temperature range. Its coefficient of thermal expansion is close to that of metal pipelines, preventing cracking. During construction, thick coatings and uniform coverage of complex curved surfaces can be achieved by adjusting viscosity and thixotropy. Moreover, its low curing shrinkage rate and strong controllability ensure long-term sealing. Compared to other resins such as polyester resin (poor corrosion resistance and large shrinkage) and polyurethane (insufficient temperature resistance), the epoxy system combines high cost-effectiveness with mature engineering verification, making it the optimal choice for harsh working conditions.

[0013] Asphalt itself has flexibility and ductility, which can effectively neutralize the brittleness of epoxy resin after curing.

[0014] Diaminodiphenylmethane (DDM) molecules contain two active amino groups (-NH2), which can undergo ring-opening addition reactions with epoxy groups in epoxy resins to form hydroxyl groups and carbon-nitrogen bonds, gradually building a highly cross-linked three-dimensional network structure, which can improve the mechanical strength, heat resistance and chemical stability of composite coatings.

[0015] In one or more embodiments, the glycidyl ether comprises glycerol triglycidyl ether (GGE). Existing glycidyl ethers such as butyl glycidyl ether, ethylene glycol diglycidyl ether, propoxylated glycerol glycidyl ether, and 1,4-butanediol glycidyl ether are, on the whole, inferior to glycerol triglycidyl ether (GGE). The specific reason is that the glycerol triglycidyl ether molecule contains three epoxy groups (C... 12 H 20 O6), during curing, can participate in both chain and network crosslinking reactions, significantly improving the tensile strength, compressive strength, and impact resistance of the coating. Butyl glycidyl ether, however, contains only one epoxy group, resulting in low crosslinking density and brittle, poor-temperature-resistant coatings after curing. Ethylene glycol diglycidyl ether has relatively insufficient mechanical strength and chemical resistance. Propoxylated glycerol glycidyl ether is more expensive. 1,4-Butanediol glycidyl ether contains two epoxy groups (C... 10 H 18 O4) forms a chain-like cross-linked structure, which can effectively improve flexibility, but the cross-linking density is low and the mechanical strength is low.

[0016] In this invention, glycidyl ether solves the problems of high viscosity, high brittleness, and poor weather resistance of traditional epoxy resins by dilution, toughening, crosslinking, and chemical stability regulation.

[0017] Secondly, the present invention provides a method for preparing the above-mentioned carbon fiber reinforced resin-based composite coating, comprising the following steps:

[0018] Pretreated carbon fibers are immersed in a curing agent to obtain a curing agent mixture that wets the carbon fibers;

[0019] Epoxy resin, asphalt, diaminodiphenylmethane and glycidyl ether are mixed, and then mixed with the curing agent mixture that impregnates the carbon fibers to obtain a resin mixture;

[0020] The resin mixture is coated onto the pretreated substrate surface and cured at room temperature.

[0021] In one or more embodiments, the specific steps of the pretreated carbon fiber include: immersing the carbon fiber in an acid solution, allowing it to stand, removing it, and washing it to obtain the final product.

[0022] Preferably, the pH of the acid solution is 5-6.

[0023] Preferably, the settling time is 6-12 hours.

[0024] Preferably, the cleaning process involves sequentially cleaning with water and anhydrous ethanol to remove any residual acid solution from the surface of the carbon fiber.

[0025] In one or more embodiments, the carbon fibers need to be cleaned and dried before pretreatment. Specifically, anhydrous ethanol is used to clean surface impurities, and after drying, pure and dry carbon fibers are obtained.

[0026] In one or more embodiments, the pretreated carbon fibers are immersed in the curing agent and then allowed to stand for 1-3 hours to mix thoroughly.

[0027] In one or more embodiments, the resin mixture also needs to be placed in a vacuum drying environment for 5 to 10 minutes to eliminate air bubbles generated during the curing reaction.

[0028] In one or more embodiments, the pretreated substrate surface includes: sanding, cleaning, and drying the substrate surface. Specifically, the substrate surface is sanded with sandpaper, cleaned with acetone and ethanol using ultrasonic vibration, and then wiped clean and dried for later use.

[0029] In one or more embodiments, the curing time at room temperature is 20-40 minutes.

[0030] Thirdly, the present invention provides the application of the above-mentioned carbon fiber reinforced resin-based composite coating in pipelines. Preferably, it is used in rapid pipeline sealing.

[0031] Fourthly, the present invention provides a pipe comprising the above-described carbon fiber reinforced resin-based composite coating.

[0032] One or more of the above technical solutions have the following advantages or beneficial effects:

[0033] (1) The presence of CFs prevents the directional propagation of cracks, resulting in uneven and irregular fractures in the cross-section of the CFs@EP composite coating. Furthermore, the interface between CFs and EP is tightly bonded, which is beneficial for improving the mechanical properties of the composite coating. The presence of CFs significantly increases the glass transition temperature and thermal stability of the resin, facilitating the application of the CFs@EP composite coating in more severe working conditions. The introduced CFs can significantly increase the impermeability of the coating, providing long-term corrosion protection. Therefore, the CFs@EP composite coating (carbon fiber-epoxy resin composite coating) prepared at room temperature in this invention has a high curing rate and excellent corrosion resistance and toughness, making it suitable for rapid pipeline sealing in harsh environments, providing insights for its application in the field of oil and gas pipeline repair.

[0034] (2) Both the ordinary commercial resin and the CFs@EP resin prepared in this invention showed good fluidity after preparation. However, after standing for 30 minutes and then tilting again, the CFs@EP resin had completely cured and lost its fluidity compared to the ordinary commercial resin, while the ordinary commercial resin still showed good fluidity, indicating that the CFs@EP resin has a high curing rate.

[0035] (3) Compared with pure EP coating, the composite coating containing CFs exhibits a higher impedance value; with the increase of immersion time, the phase angle of the pure EP coating decreases significantly after 30 days, but during the 50-day immersion process, the phase of the CFs@EP composite coating remains at a high position; although the capacitive arc radius of the CFs@EP composite coating shows a decreasing trend compared with the pure EP coating, its capacitive arc radius is still an order of magnitude higher than that of pure EP. Therefore, the introduction of CFs can significantly increase the impermeability of the coating and has long-term corrosion protection capability.

[0036] (4) After 60 days of neutral salt spray test, no obvious corrosion products were found in the composite coating introduced by CFs and the coating color did not change significantly. This indicates that the densely packed CFs effectively improved the barrier ability of the coating, significantly improved the anti-corrosion performance of the composite coating, and effectively improved the environmental adaptability of the carbon fiber reinforced resin-based composite coating in pipeline sealing.

[0037] (5) The bonding strength of the CFs@EP composite coating reached a maximum of 17.95 MPa, which indicates that CFs can effectively enhance the adhesion of the coating and give the CFs@EP composite coating superior anti-corrosion performance. The tensile strength of the CFs@EP composite coating increased to 241.67 MPa and the elongation at break reached 269.8%, which indicates that the high toughness of CFs itself made a significant contribution to the improvement of the tensile strength of the composite coating. In the drop hammer impact test, when the height of the impact hammer was 30 cm, 50 cm and 70 cm, no cracks were generated in the center of the CFs@EP composite coating, which indicates that CFs significantly improved the brittleness problem after the coating was cured and greatly improved the impact resistance of the composite coating. Attached Figure Description

[0038] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0039] Figure 1 The images show the surface morphology SEM and EDS images of CFs at different magnifications according to the present invention; where a, b, and c are the surface morphology SEM images of CFs at different magnifications, and d is the EDS image of CFs.

[0040] Figure 2 The ATR-FTIR spectra of pure EP and CFs@EP coatings of this invention are shown below.

[0041] Figure 3 The images show SEM images of the brittle fracture sections of the pure EP and CFs@EP composite coatings of the present invention; where a and b are SEM images of the brittle fracture sections of the pure EP coating at different magnifications, and c and d are SEM images of the brittle fracture sections of the CFs@EP composite coating at different magnifications.

[0042] Figure 4 This is a comparison of the curing time of the common commercial resin and CFs@EP resin of the present invention; where a is the curing time of 0 min and b is the curing time of 30 min.

[0043] Figure 5 The DCS curve of the pure EP and CFs@EP composite coating of this invention;

[0044] Figure 6 The electrochemical impedance spectroscopy, phase angle diagram, and Nyquist curve of the pure EP and CFs@EP composite coating of the present invention are shown below; wherein, a1, a2, and a3 are the electrochemical impedance spectroscopy, phase angle diagram, and Nyquist curve of the pure EP coating, respectively, and b1, b2, and b3 are the electrochemical impedance spectroscopy, phase angle diagram, and Nyquist curve of the CFs@EP composite coating, respectively.

[0045] Figure 7 The images show the neutral salt spray tests of the ordinary commercial resin coating, pure EP, and CFs@EP composite coating of this invention; wherein, a1, a2, and a3 are optical photographs of the ordinary commercial resin coating at different test times in the neutral salt spray test, b1, b2, and b3 are optical photographs of the pure EP coating at different test times in the neutral salt spray test, and c1, c2, and c3 are optical photographs of the CFs@EP composite coating at different test times in the neutral salt spray test.

[0046] Figure 8 The images show the adhesion test results of the pure EP and CFs@EP composite coatings of this invention; where a is a comparison of the adhesion effects of the pure EP and CFs@EP composite coatings, b is a physical result image of the pure EP after the adhesion test experiment, and c is a physical result image of the CFs@EP composite coating after the adhesion test experiment.

[0047] Figure 9 Tensile test, stress-strain curve, tensile strength and elongation of the pure EP and CFs@EP composite coating of the present invention are shown in the figure. Among them, a is a comparison figure of the tensile test of the pure EP and CFs@EP composite coating, b is a comparison figure of the stress-strain curve of the pure EP and CFs@EP composite coating, c is a comparison figure of the tensile strength of the pure EP and CFs@EP composite coating, and d is a comparison figure of the elongation of the pure EP and CFs@EP composite coating.

[0048] Figure 10 The results are from drop hammer impact tests of the pure EP coating and the CFs@EP composite coating of this invention under different height conditions. Detailed Implementation

[0049] The carbon fiber cloth used in this invention was provided by Toray Industries, Inc. of Japan, and its model number is T-300.

[0050] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0051] Example 1

[0052] 1. Use 200-grit and 600-grit sandpaper respectively to sand an area of ​​1 cm². 2 and 10cm 2 The Q235 carbon steel was polished and cleaned with acetone and ethanol using ultrasonic vibration. After wiping and drying, it was ready for use. (Note that 1cm...) 2 It's for electrochemical experiments, 10cm 2 It's used for salt spray testing.

[0053] 2. Before pretreatment of CFs, surface impurities are cleaned with anhydrous ethanol and dried to obtain pure and dry CFs.

[0054] 3. Immerse the CFs in an aqueous solution prepared with hydrochloric acid (pH=5), let it stand for 6 hours, and then take it out and wash off the acid solution residue on the surface of the CFs with deionized water and anhydrous ethanol to obtain pretreated CFs.

[0055] 4. Immerse 1.5g of pretreated CFs in 4.0g of polyetheramine D-400 curing agent and let stand for 1.5h to allow the CFs to fully combine with the curing agent.

[0056] 5. Thoroughly mix 10g of E51 resin, 1.25g of asphalt, 1.5g of diaminodiphenylmethane (DDM), and 1.5g of glycerol triglycidyl ether (GGE). Pour the mixture into the curing agent impregnating the CFs and stir slowly to ensure thorough mixing. To eliminate air bubbles generated during the curing reaction, place the resin mixture in a vacuum drying oven and degas for 5-10 minutes.

[0057] 6. Apply the resin mixture to the pre-treated carbon steel surface using a wire bar coater and cure at room temperature for 30 minutes to obtain a carbon fiber-epoxy resin composite coating, denoted as CFs@EP.

[0058] Example 2

[0059] Unlike Example 1, the epoxy resin used is E44.

[0060] Comparative Example 1:

[0061] 1. Use 200-grit and 600-grit sandpaper respectively to sand an area of ​​1 cm². 2 and 10cm 2 The Q235 carbon steel was polished and cleaned with acetone and ethanol using ultrasonic vibration. After wiping and drying, it was ready for use.

[0062] 2. Thoroughly mix 10g E51 resin, 4g polyetheramine D-400 curing agent, 1.25g asphalt, 1.5g diaminodiphenylmethane (DDM), and 1.5g glycerol triglycidyl ether (GGE). To eliminate air bubbles generated during the curing reaction, place the resin mixture in a vacuum drying oven and evacuate for 5-10 minutes.

[0063] 3. The resin mixture is applied to the pre-treated carbon steel surface using a wire bar coater and cured at room temperature for 30 minutes to obtain a carbon fiber-epoxy resin composite coating, denoted as EP.

[0064] Comparative Example 2

[0065] Unlike Example 1, the order in which the resin, curing agent, and carbon fiber are added in steps 4 and 5 is different. The resin and curing agent are mixed first, and then the carbon fiber is impregnated. The specific steps are as follows:

[0066] E51 resin, asphalt, diaminodiphenylmethane (DDM), glycerol triglycidyl ether (GGE), and curing agent are thoroughly mixed in proportion, allowed to stand, and then impregnated with carbon fiber to ensure thorough mixing, thus obtaining a resin mixture. The mixture is then placed in a vacuum drying oven and evacuated for 5-10 minutes.

[0067] Comparative Example 3

[0068] Unlike Example 1, the order in which the resin, curing agent, and carbon fiber are added in steps 4 and 5 is different. Instead, the carbon fiber, resin, and curing agent are directly mixed. The specific steps are as follows:

[0069] E51 resin, asphalt, diaminodiphenylmethane (DDM), glycerol triglycidyl ether (GGE), curing agent, and carbon fiber are thoroughly mixed in proportion and allowed to stand to obtain a resin mixture. The mixture is then placed in a vacuum drying oven and evacuated for 5-10 minutes.

[0070] Comparative Example 4

[0071] Unlike Example 1, the order in which the resin, curing agent, and carbon fiber are added in steps 4 and 5 is different. First, the epoxy resin and carbon fiber are mixed, and then the curing agent is mixed in. The specific steps are as follows:

[0072] E51 resin, asphalt, diaminodiphenylmethane (DDM), and glycerol triglycidyl ether (GGE) are thoroughly mixed in a certain proportion and then impregnated into carbon fibers. A curing agent is then added to obtain the resin mixture, which is then placed in a vacuum drying oven and degassed for 5-10 minutes.

[0073] Table 1 Comparison of mechanical properties between Example 1 and Comparative Examples 1-4

[0074]

[0075] Before the curing agent reacts with the resin, its viscosity is low, allowing the curing agent to more fully wet the carbon fiber surface and micropores. Furthermore, the uncured, low-viscosity resin can penetrate deep into these microstructures, enhancing interfacial bonding through a combination of mechanical and chemical bonding. However, if the curing agent is mixed first, the resin viscosity will rise rapidly due to the pre-curing reaction, resulting in insufficient fiber wetting and increased interfacial porosity.

[0076] After treatment, the surface of carbon fiber is rich in active groups such as hydroxyl (-OH) and carboxyl (-COOH). When it comes into contact with resin first, the epoxy groups (-O-) in the resin can react directly with the groups on the fiber surface to form chemical bonds (such as ether bonds and ester bonds). However, when the curing agent is added later, it reacts preferentially with the resin, reducing the chance of direct bonding between the fiber and the resin.

[0077] Figure 1SEM and EDS images of the surface morphology of carbon fibers at different magnifications are shown. Figure 1 As can be seen in (a) above, the vast majority of carbon fibers are arranged in parallel and are relatively densely packed. According to Figure 1 The data in (b) show that the carbon fibers are relatively uniform in thickness, with diameters ranging from 4.5 μm to 4.8 μm. Further magnification reveals... Figure 1 As shown in (c), the carbon fiber surface is relatively smooth, and after the pretreatment process, a small number of narrow grooves exist along the fiber length direction. Furthermore, Figure 1 The EDS spectrum of (d) further indicates the carbon content in the carbon fiber.

[0078] like Figure 2 As shown, in the FTIR spectra of EP and CFs@EP, a region between 3200 and 3600 cm⁻¹ can be observed. -1 A typical broad and strong peak appeared within the range, which is caused by the stretching vibration of OH groups of water adsorbed on the resin surface. (2923 and 2849 cm⁻¹) -1 The peak values ​​at 1508 and 826 cm⁻¹ are caused by the asymmetric and symmetric stretching vibrations of methylene-CH, respectively. -1 The peaks at 1736, 1608, and 1038 cm⁻¹ are attributed to the stretching vibration of methyl-CH. These peaks are observed at 1736, 1608, and 1038 cm⁻¹. -1 The typical absorbance peaks at these locations are due to the stretching vibrations of -C=O, C=C, and -CO in the epoxy coating. Furthermore, due to the stretching vibrations of -CH and -CO in the CFs, peaks can be observed at 2923, 2849, 1508, and 1038 cm⁻¹. -1 The peak intensity at the point of origin increased significantly, thus proving the presence of CFs in the EP.

[0079] Figure 3 The morphology of the brittle fracture sections of the pure EP coating and the CFs@EP composite coating were analyzed using SEM. Figure 3 As can be seen in (a) of the image, the cross-section of the pure EP coating is relatively smooth. Looking further magnified, as... Figure 3 As shown in (b), a few small pores can still be observed in the pure EP coating. When CFs are added to the epoxy resin, as... Figure 3 As shown in (c), the cross-section of the CFs@EP composite coating exhibits uneven and irregular fracture, which is due to the presence of CFs preventing the directional propagation of cracks. Furthermore, from... Figure 3 In the magnified cross-section of the CFs@EP composite coating in (d), it can be observed that the interface between CFs and EP is relatively tight, which is beneficial to improving the mechanical properties of the composite coating.

[0080] Figure 4This is a comparison of the curing times of ordinary commercial resin (Phoenix brand E44 epoxy resin) and CFs@EP resin. From... Figure 4 As shown in (a), both the commercial resin and the CFs@EP resin exhibited good flowability after formulation, and were then placed back in their original positions. After standing for 30 minutes, both resins were tilted again. Figure 4 As shown in (b), the CFs@EP resin has completely cured and lost its fluidity, while ordinary commercial resin still exhibits good fluidity, thus confirming that the CFs@EP resin has a high curing rate. Furthermore, in this invention, the shortest curing time for the CFs@EP resin is approximately 25 minutes.

[0081] Figure 5 The DCS curves of pure EP and CFs@EP composite coatings are shown, and the corresponding glass transition temperatures are calculated. The figure shows that the glass transition temperature of pure EP is approximately 72℃, while that of the CFs@EP composite coating is approximately 85℃. This demonstrates that the presence of CFs significantly improves the glass transition temperature and thermal stability of the resin, facilitating the application of CFs@EP composite coatings in more demanding working conditions.

[0082] like Figure 6 As shown, EIS testing was used to evaluate the electrochemical behavior and protection mechanism of the pure EP / CFs@EP composite coating. The barrier performance of the resin-based coating against corrosive media can be assessed through specific frequencies (Z). f=0.01Hz The impedance modulus under these conditions is reflected in the impedance. It can be seen that as the immersion time increases, the impedance of pure EP in the low-frequency region decreases over time. For example... Figure 6 As shown in a1, the initial impedance of pure EP is 1.49 × 10⁻⁶. 10 Ω cm 2 After soaking for 15 days, the concentration dropped to 1.08 × 10⁻⁶. 10 Ω cm 2 The impedance modulus (Z) of pure EP after soaking for 30 days. f=0.01Hz It dropped rapidly to 2.64 × 10 9 Ω cm 2 This indicates that corrosion particles have reached the substrate / coating interface and begun to corrode the metal. With further extension of immersion time, the impedance modulus of pure EP decreased to 1.03 × 10⁻⁶ after 50 days. 9 Ω cm 2 Due to micro-defects such as pores present during the preparation of pure EP coatings, their resistance to electrolyte corrosion is difficult to meet the practical requirements for long-term use, thus limiting their anti-corrosion performance. Compared to pure EP coatings, composite coatings containing CFs exhibit higher impedance values, such as... Figure 6 As shown in b1 in the diagram. Specifically, the impedance modulus (Z) f=0.01HzAfter soaking for 5 days, the concentration reached 8.08 × 10⁻⁶. 10 Ω cm 2 After soaking for 15 days, the value was 3.90 × 10⁻⁶. 10 Ω cm 2 And remain relatively stable. Over time, the impedance value decreases slightly, and after 30 days of immersion, the low-frequency (Z) value... f=0.01Hz The impedance value is 2.27 × 10⁻⁶. 10 Ω cm 2 This indicates that the electrochemical process at the metal / coating interface is significantly suppressed, and the composite coating exhibits excellent protective performance. Even after 50 days of immersion, the low-frequency impedance of the CFs@EP composite coating remains at 1.39 × 10⁻⁶. 10 Ω cm 2 The above suggests that the introduced CFs can significantly increase the impermeability of the coating and provide long-term corrosion protection. The degree of corrosion and the process of damage to the substrate can be reflected in the changes in the Bode phase diagram, such as... Figure 6 As shown in a2 and b2, corrosion products generated at the interface between the metal substrate and the coating can disrupt the interfacial bonding, reduce coating adhesion, and lead to coating peeling. From Figure 6 As can be seen in a2, the phase angle of the pure EP coating decreased significantly after 30 days with increasing immersion time. However, during the 50-day immersion process, the phase of the CFs@EP composite coating remained at a high position. Figure 6 a3 and b3 in the figure represent the Nyquist curves of the pure EP and CFs@EP composite coating after 50 days in a 3.5 wt.% NaCl solution. The magnitude of the capacitive arc can approximately reflect the anti-corrosion performance of the coating. For the pure EP coating, its capacitive arc decreases continuously with increasing immersion time, such as... Figure 6 As shown in a3, this indicates that the coating's anti-corrosion effect on the metal is weakened. Compared with the pure EP coating, although the capacitive arc radius of the CFs@EP composite coating shows a decreasing trend, its capacitive arc radius is still an order of magnitude higher than that of pure EP. The above results further confirm that the CFs@EP composite coating has superior long-term corrosion resistance.

[0083] Figure 7 Optical photographs of different samples during salt spray testing. (Example) Figure 7 As shown in (a), after 30 days of testing, the ordinary commercial coating exhibited significant pitting corrosion and produced a large amount of rust. As the testing time increased to 60 days, corrosive rust accumulated in the damaged areas of the coating and covered the sample surface. This is mainly attributed to the penetration and diffusion of corrosive ions from the scratched areas into the coating substrate, indicating its poor barrier properties. Figure 7As observed in (b), the pure EP coating developed a small number of white spots after 30 days, and after 60 days, the coating color lightened with the aggregation of tiny white spots, indicating that water molecules had penetrated into the coating. However, after a 60-day neutral salt spray test, no obvious corrosion products were found in the composite coating introduced by CFs, and the coating color did not change significantly. Figure 7 As shown in (b) above, the densely packed CFs effectively improve the barrier properties of the coating, significantly enhance the corrosion resistance of the composite coating, and effectively improve the environmental adaptability of the carbon fiber reinforced resin-based composite coating in pipeline sealing.

[0084] The adhesion of pure EP coating and CFs@EP composite coating to carbon steel surfaces was tested using a pull-out test. Figure 8 As can be seen, the adhesion strength of the pure EP coating is 4.14 MPa, while the CFs@EP composite coating reaches a maximum of 17.95 MPa, which is 3.3 times higher than that of the pure EP coating. The tightly arranged CFs bond well with the resin, reducing the voids in the coating matrix and enhancing the interfacial bonding strength between resins. In addition, CFs can effectively enhance the adhesion of the coating, giving the CFs@EP composite coating superior anti-corrosion performance.

[0085] Tensile tests were performed on the pure EP and CFs@EP composite coating using a universal testing machine to evaluate the effect of CFs on the tensile strength of the coating. Figure 9 As shown in 'a'. The result is as follows: Figure 9 As shown in Figure bd, the tensile strength of pure EP is 36.26 MPa, and the elongation at break is 98.58%. After introducing CFs, the tensile strength of the CFs@EP composite coating increases to 241.67 MPa, and the elongation at break reaches 269.8%. Compared with the pure EP coating, the tensile strength and elongation at break of the CFs@EP composite coating are increased by 5.7 times and 1.7 times, respectively. Analysis shows that the high strength and toughness of CFs themselves make a significant contribution to the improvement of the tensile strength of the composite coating. In addition, the presence of CFs fills a large number of defects such as pores and cracks in the coating. Therefore, the CFs@EP composite coating has great advantages in the field of live sealing of oil and gas pipelines.

[0086] Cured epoxy resin itself is somewhat brittle, and the high crosslinking density results in poor crack propagation resistance in the coating, limiting its application in rapid pipe sealing. Therefore, the impact resistance of pure EP coating and CFs@EP composite coating was evaluated using a drop hammer impact test. The results are as follows: Figure 10 As shown. From Figure 10In figures a1, a2, b1, and b2, it can be observed that when the impact hammer height is 30cm, the pure EP coating exhibits obvious cracks that extend radially outwards, with a length of approximately 8-10mm. However, at the same impact hammer height, the CFs@EP composite coating surface shows no change. Further increasing the impact hammer height to 50cm, the CFs@EP composite coating surface still shows no significant change, as shown... Figure 10 As shown in c1 and c2, when the impact hammer height is raised again to 70cm, a slight deformation can be observed at the center of the CFs@EP composite coating, but no cracks are produced. Figure 10 As shown in d1 and d2, the above results demonstrate that CFs significantly improve the brittleness problem after coating curing and greatly enhance the impact resistance of the composite coating. The CFs@EP composite coating helps improve the protection against mechanical damage after pipeline sealing.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A carbon fiber reinforced resin-based composite coating, characterized in that, It includes the following components by weight: 0.5-2 parts carbon fiber, 3-5 parts curing agent, 8-12 parts epoxy resin, 1-1.5 parts asphalt, 1-2 parts diaminodiphenylmethane, and 1-2 parts glycidyl ether. The curing agent is an amine curing agent, which is one or more of polyetheramine curing agents and aliphatic amine curing agents, and the polyetheramine curing agent is one or more of D230, D400, T403, D2000 and T5000; The epoxy resin is one or more of E51 resin and E44 resin; The glycidyl ether includes glycerol triglycidyl ether; The method for preparing the carbon fiber reinforced resin-based composite coating includes the following steps: Pretreated carbon fibers are immersed in a curing agent to obtain a curing agent mixture that wets the carbon fibers; Epoxy resin, asphalt, diaminodiphenylmethane and glycidyl ether are mixed, and then mixed with the curing agent mixture that impregnates the carbon fibers to obtain a resin mixture; The resin mixture is coated onto the pretreated substrate surface and cured at room temperature.

2. The carbon fiber reinforced resin-based composite coating according to claim 1, characterized in that, The carbon fiber includes carbon fiber cloth; The polyetheramine curing agent is D400; The epoxy resin is E51 resin.

3. A method for preparing the carbon fiber reinforced resin-based composite coating according to claim 1 or 2, characterized in that, Includes the following steps: Pretreated carbon fibers are immersed in a curing agent to obtain a curing agent mixture that wets the carbon fibers; Epoxy resin, asphalt, diaminodiphenylmethane and glycidyl ether are mixed, and then mixed with the curing agent mixture that impregnates the carbon fibers to obtain a resin mixture; The resin mixture is coated onto the pretreated substrate surface and cured at room temperature.

4. The preparation method according to claim 3, characterized in that, The specific steps for pretreating the carbon fiber include: immersing the carbon fiber in an acid solution, allowing it to stand, then removing and washing it to obtain the final product. The pH of the acid solution is 5-6; The settling time is 6-12 hours; The cleaning process involves sequentially cleaning with water and anhydrous ethanol.

5. The preparation method according to claim 3, characterized in that, Before carbon fiber pretreatment, it is necessary to clean and dry the carbon fiber.

6. The preparation method according to claim 3, characterized in that, The pretreated carbon fibers are immersed in the curing agent and allowed to stand for 1-3 hours to mix thoroughly.

7. The preparation method according to claim 3, characterized in that, The resin mixture also needs to be placed in a vacuum drying environment and evacuated for 5-10 minutes.

8. The preparation method according to claim 3, characterized in that, The pretreated substrate surface includes: sanding the substrate surface with sandpaper, cleaning it with acetone and ethanol through ultrasonic vibration, wiping it clean and drying it for later use.

9. The application of a carbon fiber reinforced resin-based composite coating as described in claim 1 or 2 and / or a carbon fiber reinforced resin-based composite coating obtained by any one of claims 3-8 in rapid pipe sealing.

10. A pipe comprising the carbon fiber reinforced resin-based composite coating of claim 1 or 2 and / or the carbon fiber reinforced resin-based composite coating obtained by the preparation method of any one of claims 3-8.

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