Carbon fiber reinforced resin-based composite coating as well as preparation method and application thereof

Abstract

The invention discloses a carbon fiber reinforced resin-based composite coating as well as 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 comprises the following steps: immersing pretreated carbon fibers into a curing agent to obtain a curing agent mixture infiltrated with the carbon fibers; mixing epoxy resin, asphalt, diaminodiphenyl methane and glycidyl ether, and mixing the mixture with the curing agent mixture infiltrating the carbon fibers to obtain a resin mixture; and coating the surface of a pretreated matrix with the resin mixture, and curing at room temperature. The carbon fiber reinforced resin-based composite coating prepared by the process disclosed by the invention has higher curing rate and excellent corrosion resistance and toughness, can be suitable for quickly plugging a pipeline in a severe environment, and provides 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] The present invention belongs to the technical field of pipeline corrosion protection, and in particular relates to a carbon fiber reinforced resin-based composite coating and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] As pipelines age, some older networks experience corrosion, thinning, and even leaks, necessitating frequent plugging operations. However, traditional pipeline repair methods often suffer from significant operational impact, prolonged downtime, low repair efficiency, significant safety hazards, and slow response times. These methods fail to meet the urgent need for rapid, efficient, and safe operation of modern oil and gas pipelines. Therefore, a new rapid pipeline plugging technology is needed.

[0004] The rapid pipeline plugging technology can quickly and effectively plug pipeline leaks without interrupting the flow of water, thereby greatly shortening maintenance time and improving maintenance efficiency. At present, a variety of mature methods and technical systems have been formed for rapid pipeline plugging technology, among which the technologies for external pipeline repair mainly include clamp plugging method and repair glue plugging method. The pipeline clamp plugging method uses a specially designed pipeline clamp, puts it on the pipeline, and bolts the two clamps tightly together to effectively block the pipeline. This technology is suitable for situations where the pipeline diameter is small, and the clamp is prone to corrosion in a hot and humid environment, causing secondary leakage. The repair glue plugging method only requires applying resin glue to the cut or leak point of the pipeline and letting it cure naturally to form a solid sealing layer. This method is easy to operate and is suitable for a variety of pipeline materials and sizes. However, traditional polymer resin glue still has problems such as slow curing speed, high brittleness after curing, poor corrosion resistance in harsh environments, and substandard strength and toughness, which limits its application in the field of rapid pipeline plugging.‌

[0005] Fiber materials are widely used in polymer coatings due to their high strength, good flexibility and toughness, corrosion resistance, and diverse application forms. Fiber materials (such as glass fiber and polyester fiber) can generally withstand large tensile and compressive forces and are suitable for applications that require high loads, such as pipeline repair and reinforcement. In addition, fiber materials can bend and twist to a large extent without breaking easily, allowing them to fit tightly when filling gaps or wrapping pipes, reducing the possibility of shrinkage deformation and cracking. Fiber materials also have good corrosion resistance and can resist the erosion of chemical substances, maintaining long-term stability and durability. Finally, fiber materials can be in the form of fiber cloth, fiber tape, or fiber rope, which is convenient for construction and operation. They can be easily combined with other materials (such as resins) to form composite materials, which facilitates the application of fiber composite materials in the field of rapid pipeline plugging. Summary of the Invention

[0006] In order to address the shortcomings of the existing technology, the purpose of the present invention is to provide a carbon fiber reinforced resin-based composite coating and its preparation method and application. For the rapid curing coating system, carbon fiber cloth (CFs) is introduced into the epoxy resin coating, and the interface bonding between CFs and the resin and the filling of defects such as pores and cracks in the resin coating by CFs are explored. The influence of CFs on the toughness, corrosion resistance and bonding strength of the composite coating is analyzed, and its application advantages in pipeline rapid plugging technology are explained.

[0007] In order to achieve the above object, the technical solution of the present invention is: 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 of carbon fiber, 3-5 parts of curing agent, 8-12 parts of epoxy resin, 1-1.5 parts of asphalt, 1-2 parts of diaminodiphenylmethane, and 1-2 parts of glycidyl ether.

[0008] In one or more embodiments, the carbon fibers include carbon fiber cloth (CFs).

[0009] Carbon fiber can be used directly or in a carbon fiber cloth. Carbon fiber cloth offers superior performance. In carbon fiber cloth, the majority of carbon fibers are arranged in parallel and densely. The carbon fibers are relatively uniform in thickness, with diameters ranging from 4.5 μm to 4.8 μm. There are no specific restrictions on the texture of the carbon fiber cloth; for example, plain weave can be used in the examples.

[0010] In one or more embodiments, the curing agent is an amine curing agent, including 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.

[0011] In one or more embodiments, the epoxy resin includes E51 resin and E44 resin, preferably E51 resin. Epoxy resin forms strong chemical bonds and physical anchors with carbon fibers by virtue of polar groups such as hydroxyl groups and ether bonds, ensuring high interfacial bonding strength, and has a high crosslinking density after curing, giving the coating high modulus, creep resistance, and fatigue resistance. Its chemical inertness can withstand acid, alkali, oil and gas corrosive media and a wide temperature range, and its thermal expansion coefficient is close to that of metal pipelines, avoiding cracking. During construction, thick coating and uniform coverage of complex curved surfaces are achieved by adjusting viscosity and thixotropy, and the curing shrinkage is low and highly controllable, ensuring long-term sealing. Compared with other resins such as polyester resin (poor corrosion resistance, large shrinkage) and polyurethane (insufficient temperature resistance), the epoxy system has both high cost performance and mature engineering verification, making it the best choice under harsh working conditions.

[0012] Asphalt itself is flexible and ductile, which can effectively neutralize the brittleness of epoxy resin after curing.

[0013] The diaminodiphenylmethane (DDM) molecule contains two active amino groups (-NH2), which can undergo a ring-opening addition reaction with the epoxy groups in the epoxy resin 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 the composite coating.

[0014] In one or more embodiments, the glycidyl ether includes 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 generally 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), can participate in chain and network cross-linking reactions during curing, significantly improving the tensile strength, compressive strength and impact resistance of the coating. However, butyl glycidyl ether contains only one epoxy group and has a low cross-linking density. After curing, the coating is brittle and has poor temperature resistance. The mechanical strength and chemical resistance of ethylene glycol diglycidyl ether are relatively insufficient. The cost of propoxylated glycerol glycidyl ether is relatively high. 1,4-Butanediol glycidyl ether contains two epoxy groups (C 10 H 18 O4), forming a chain cross-linked structure, which can effectively improve flexibility, but the cross-linking density is low and the mechanical strength is low.

[0015] In the present invention, glycidyl ether solves the problems of traditional epoxy resins such as high viscosity, high brittleness and poor weather resistance through dilution, toughening, cross-linking and chemical stability regulation.

[0016] In a second aspect, the present invention provides a method for preparing the above-mentioned carbon fiber reinforced resin-based composite coating, comprising the following steps: impregnating the pretreated carbon fiber into a curing agent to obtain a curing agent mixture that impregnates the carbon fiber; mixing epoxy resin, asphalt, diaminodiphenylmethane and glycidyl ether, and mixing the mixture with the curing agent mixture impregnating the carbon fiber to obtain a resin mixture; The resin mixture is coated on the pre-treated substrate surface and cured at room temperature.

[0017] In one or more embodiments, the specific steps of pre-treating the carbon fiber include: immersing the carbon fiber in an acid solution, letting it stand, taking it out, and washing it.

[0018] Preferably, the pH of the acid solution is 5-6.

[0019] Preferably, the standing time is 6-12 hours.

[0020] Preferably, the cleaning is performed by successively using water and anhydrous ethanol, the purpose of which is to clean away the acid solution residue on the surface of the carbon fiber.

[0021] In one or more embodiments, the carbon fibers are cleaned and dried before being pretreated, specifically by using anhydrous ethanol to clean surface impurities and drying to obtain pure and dry carbon fibers.

[0022] In one or more embodiments, the pretreated carbon fiber is immersed in the curing agent and needs to be left standing to be fully mixed, and the standing time is 1-3 hours.

[0023] In one or more embodiments, the resin mixture also needs to be placed in a vacuum drying environment and evacuated for 5 to 10 minutes to eliminate bubbles generated during the curing reaction.

[0024] In one or more embodiments, the pretreatment of the substrate surface includes polishing, cleaning, and drying the substrate surface. Specifically, the substrate surface is polished with sandpaper, cleaned with acetone and ethanol by ultrasonic vibration, and then wiped and dried for later use.

[0025] In one or more embodiments, the curing time at room temperature is 20-40 minutes.

[0026] In a third aspect, the present invention provides the use of the carbon fiber reinforced resin-based composite coating in pipelines, preferably in rapid pipeline plugging.

[0027] In a fourth aspect, the present invention provides a pipeline comprising the above-mentioned carbon fiber reinforced resin-based composite coating.

[0028] One or more of the above technical solutions have the following advantages or beneficial effects: (1) The presence of CFs prevents the directional expansion of cracks, resulting in uneven and irregular fractures on the cross section of the CFs@EP composite coating, and the interface between CFs and EP is relatively tight, which is beneficial to improving the mechanical properties of the composite coating. The presence of CFs significantly increases the glass transition temperature and thermal stability of the resin, which helps the CFs@EP composite coating to be applied to more severe working conditions. The introduced CFs can significantly increase the anti-seepage performance of the coating and provide long-term corrosion protection. Therefore, the CFs@EP composite coating (carbon fiber-epoxy resin composite coating) prepared at room temperature in the present invention has a high curing rate and excellent corrosion resistance and toughness, and can be used for rapid sealing of pipelines in harsh environments, providing ideas for its application in the field of oil and gas pipeline repair.

[0029] (2) Both the common commercial resin and the CFs@EP resin prepared by the present invention exhibited good fluidity after preparation. However, when tilted again after standing for 30 minutes, the CFs@EP resin had completely solidified and lost its fluidity compared to the common commercial resin, while the common commercial resin still exhibited good fluidity, indicating that the CFs@EP resin had a higher curing rate.

[0030] (3) Compared with the pure EP coating, the composite coating containing CFs exhibited a higher impedance value. With the increase of immersion time, the phase angle of the pure EP coating decreased significantly after 30 days. However, during the 50-day immersion process, the phase of the CFs@EP composite coating remained at a higher position. Compared with the pure EP coating, the capacitance arc radius of the CFs@EP composite coating showed a decreasing trend, but its capacitance arc radius was still one order of magnitude higher than that of the pure EP. Therefore, the introduction of CFs can significantly improve the anti-seepage performance of the coating and provide long-term corrosion protection.

[0031] (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, indicating that the more closely arranged 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 plugging.

[0032] (5) The maximum bonding strength of the CFs@EP composite coating reached 17.95 MPa, which shows that CFs can effectively enhance the adhesion of the coating, making the CFs@EP composite coating have excellent 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 shows that the high toughness of CFs itself made a great contribution to the improvement of the tensile strength of the composite coating; in the drop hammer impact test, when the impact hammer height was 30 cm, 50 cm and 70 cm, no cracks were generated in the center of the CFs@EP composite coating, which shows that CFs significantly improved the brittleness problem of the coating after curing and greatly improved the impact resistance of the composite coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0034] Figure 1 The surface morphology SEM and EDS images of CFs at different magnifications of the present invention are shown; wherein a, b, and c are the surface morphology SEM images of CFs at different magnifications, and d is the EDS image of CFs; Figure 2 ATR-FTIR spectra of pure EP and CFs@EP coatings of the present invention; Figure 3 Figures a and b are SEM images of the brittle fracture cross-section of the pure EP and CFs@EP composite coatings of the present invention; wherein, a and b are SEM images of the brittle fracture cross-section of the pure EP coating at different magnifications, and c and d are SEM images of the brittle fracture cross-section of the CFs@EP composite coating at different magnifications; Figure 4 Comparison of the curing time of the common commercial resin of the present invention and the CFs@EP resin; wherein a is the curing time of 0 min, and b is the curing time of 30 min; Figure 5 DCS curves of pure EP and CFs@EP composite coatings of the present invention; Figure 6 The electrochemical impedance spectra, phase angle diagrams and Nernquist curves of the pure EP and CFs@EP composite coatings of the present invention are shown in FIG. 1 , where a1, a2 and a3 are the electrochemical impedance spectra, phase angle diagrams and Nernquist curves of the pure EP coating, respectively; and b1, b2 and b3 are the electrochemical impedance spectra, phase angle diagrams and Nernquist curves of the CFs@EP composite coating, respectively. Figure 7Neutral salt spray test of common commercial resin coating, pure EP and CFs@EP composite coating of the present invention; wherein, a1, a2, a3 are optical photographs of common commercial resin coating at different test times in neutral salt spray test, b1, b2, b3 are optical photographs of pure EP coating at different test times in neutral salt spray test, c1, c2, c3 are optical photographs of CFs@EP composite coating at different test times in neutral salt spray test; Figure 8 The adhesion test results of pure EP and CFs@EP composite coatings of the present invention are shown in Figure 1. Figure a shows the adhesion effect comparison between pure EP and CFs@EP composite coatings, Figure b shows the actual result of pure EP after adhesion test, and Figure c shows the actual result of CFs@EP composite coating after adhesion test. Figure 9 Figure 1 shows the tensile test, stress-strain curve, tensile strength and elongation of pure EP and CFs@EP composite coatings of the present invention; Figure a is a comparison of the tensile test of pure EP and CFs@EP composite coatings, Figure b is a comparison of the stress-strain curves of pure EP and CFs@EP composite coatings, Figure c is a comparison of the tensile strength of pure EP and CFs@EP composite coatings, and Figure d is a comparison of the elongation of pure EP and CFs@EP composite coatings. Figure 10 These are the drop hammer impact test results of the pure EP coating and the CFs@EP composite coating of the present invention under different height conditions. DETAILED DESCRIPTION

[0035] The carbon fiber cloth used in the present invention is provided by Toray Industries, Ltd. of Japan, and its model is T-300.

[0036] In order to enable those skilled in the art to more clearly 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.

[0037] Example 1 1. Use 200 mesh and 600 mesh sandpaper to sand the area of 1cm 2 and 10cm 2 The Q235 carbon steel is polished and cleaned with acetone and ethanol by ultrasonic vibration. It is wiped clean and dried for later use (it should be noted that 1cm 2 It is used for electrochemical experiments, 10cm 2 It is used for salt spray test).

[0038] 2. Before pre-treating CFs, the surface impurities were cleaned with anhydrous ethanol and dried to obtain pure and dry CFs.

[0039] 3. Immerse the CFs in an aqueous solution prepared with hydrochloric acid (pH = 5), let it stand for 6 hours, then take it out and wash the acid solution residue on the surface of the CFs with deionized water and anhydrous ethanol to obtain pretreated CFs.

[0040] 4. Immerse 1.5 g of pretreated CFs into 4.0 g of polyetheramine D-400 curing agent and let it stand for 1.5 h to allow the CFs and curing agent to fully combine.

[0041] 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 this mixture into the curing agent-soaked CFs and stir gently to mix thoroughly. To eliminate bubbles generated during the curing reaction, place the resin mixture in a vacuum drying oven for 5-10 minutes.

[0042] 6. Use a wire rod coater to apply the resin mixture to the pre-treated carbon steel surface and cure it at room temperature for 30 minutes to obtain a carbon fiber-epoxy resin composite coating, which is recorded as CFs@EP.

[0043] Example 2 The difference from Example 1 is that the epoxy resin is E44.

[0044] Comparative Example 1: 1. Use 200 mesh and 600 mesh sandpaper to sand the area of 1cm 2 and 10cm 2 The Q235 carbon steel is polished, cleaned with acetone and ethanol through ultrasonic vibration, wiped clean and dried for use.

[0045] 2. Thoroughly mix 10g of E51 resin, 4g of polyetheramine D-400 curing agent, 1.25g of asphalt, 1.5g of diaminodiphenylmethane (DDM), and 1.5g of glycerol triglycidyl ether (GGE). To eliminate bubbles generated during the curing reaction, place the resin mixture in a vacuum drying oven for 5-10 minutes.

[0046] 3. Use a wire rod coater to apply the resin mixture to the pre-treated carbon steel surface and cure it at room temperature for 30 minutes to obtain a carbon fiber-epoxy resin composite coating, which is recorded as EP.

[0047] Comparative Example 2 The difference from Example 1 is that the order of adding the resin, curing agent and carbon fiber 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: E51 resin, asphalt asphalt, diaminodiphenylmethane (DDM), glycerol triglycidyl ether (GGE) and curing agent are fully mixed in proportion, allowed to stand, and then impregnated into carbon fiber to obtain a resin mixture. The mixture is then placed in a vacuum drying oven for 5 to 10 minutes.

[0048] Comparative Example 3 Different from Example 1, the order of adding the resin, curing agent and carbon fiber in steps 4 and 5 is different. The carbon fiber, resin and curing agent are directly mixed. The specific steps are as follows: E51 resin, asphalt asphalt, diaminodiphenylmethane (DDM), glycerol triglycidyl ether (GGE), curing agent and carbon fiber are fully mixed in proportion, allowed to stand to obtain a resin mixture, and then placed in a vacuum drying oven for 5 to 10 minutes.

[0049] Comparative Example 4 The difference from Example 1 is that the order of adding the resin, curing agent and carbon fiber in steps 4 and 5 is different. The epoxy resin and carbon fiber are mixed first, and then mixed with the curing agent. The specific steps are as follows: E51 resin, asphalt, diaminodiphenylmethane (DDM), and glycerol triglycidyl ether (GGE) are fully mixed in proportion and then immersed into carbon fiber. Then, a curing agent is added to obtain a resin mixture, which is then placed in a vacuum drying oven for 5 to 10 minutes.

[0050] Table 1 Comparison of mechanical properties of Example 1 and Comparative Examples 1-4

[0051] Before the curing agent reacts with the resin, its viscosity is low, allowing it to more fully infiltrate the carbon fiber surface and micropores. The uncured, low-viscosity resin can penetrate these microstructures, synergistically strengthening the interfacial bond through mechanical engagement and chemical bonding. If the curing agent is mixed first, the resin viscosity will rise rapidly due to the pre-curing reaction, resulting in inadequate fiber infiltration and increased interfacial porosity.

[0052] After treatment, the carbon fiber surface is rich in active groups such as hydroxyl (-OH) and carboxyl (-COOH). When first in contact with the resin, the epoxy groups (-O-) in the resin can directly react with the fiber surface groups to form chemical bonds (such as ether bonds and ester bonds). The curing agent added later reacts preferentially with the resin, reducing the chance of direct fiber-resin bonding.

[0053] Figure 1 The SEM and EDS images of the carbon fiber surface morphology at different magnifications are shown. Figure 1 As can be seen from (a) in the figure, most of the carbon fibers are arranged in parallel and are relatively dense. Figure 1According to the data statistics in (b), the thickness of carbon fibers is relatively uniform, and their diameters are between 4.5 μm and 4.8 μm. Figure 1 As shown in (c), it can be observed that the surface of the carbon fiber is relatively smooth, and after the pretreatment process, there are a small number of narrow grooves along the length of the fiber. In addition, Figure 1 The EDS spectrum in (d) further shows the carbon content in the carbon fiber.

[0054] like Figure 2 As shown in the FTIR spectra of EP and CFs@EP, it can be observed that the -1 A typical broad and strong peak appears in the range of 2923 and 2849 cm, which is caused by the OH stretching vibration of water adsorbed on the resin surface. -1 The peaks at 1508 and 826 cm-1 are caused by the asymmetric stretching and symmetric stretching vibrations of methylene-CH, respectively. -1 The peaks at 1736, 1608 and 1038 cm are attributed to the stretching vibration of methyl-CH. -1 The typical absorbance peaks at 2923, 2849, 1508, and 1038 cm-1 are due to the stretching vibrations of -C=O, C=C, and -CO in the epoxy coating. In addition, the typical absorbance peaks at 2923, 2849, 1508, and 1038 cm-1 are due to the stretching vibrations of -CH and -CO in CFs. -1 The peak intensity at α increased significantly, proving the existence of CFs in EP.

[0055] Figure 3 The brittle fracture cross-sections of pure EP coating and CFs@EP composite coating were analyzed by SEM. Figure 3 As can be seen in (a), the cross section of the pure EP coating is relatively smooth. Figure 3 As shown in (b), it can be observed that there are still a few small pores in the pure EP coating. Figure 3 As shown in (c), the cross section of the CFs@EP composite coating shows uneven and irregular fractures, which is due to the presence of CFs preventing the directional expansion of cracks. Figure 3 In the enlarged 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.

[0056] Figure 4 Comparison of the curing time of common commercial resin (Phoenix brand E44 epoxy resin) and CFs@EP resin. Figure 4As can be seen from (a) in the figure, both commercial resin and CFs@EP resin showed good fluidity after preparation, and then were placed back to their original positions. Figure 4 As can be seen in (b), the CFs@EP resin has completely cured and lost its fluidity, while the standard commercial resin still exhibits good fluidity, confirming the high curing rate of the CFs@EP resin. Furthermore, in the present invention, the minimum curing time of the CFs@EP resin is approximately 25 minutes.

[0057] Figure 5 The DCS curves of pure EP and the CFs@EP composite coating are shown, and the corresponding glass transition temperatures are calculated. As can be seen from the figure, the glass transition temperature of pure EP is approximately 72°C, while that of the CFs@EP composite coating is approximately 85°C. This demonstrates that 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 demanding operating conditions.

[0058] like Figure 6 As shown in Figure 2, EIS tests were used to evaluate the electrochemical behavior and protection mechanism of pure EP and CFs@EP composite coatings. The barrier performance of the resin-based coating to corrosive media can be measured by the specific frequency (Z f=0.01Hz ) is reflected in the impedance modulus under . It can be seen from the graph that as the immersion time increases, the impedance of pure EP in the low frequency region decreases over time. Figure 6 As shown in a1 in the figure, the initial impedance of pure EP is 1.49×10 10 Ω cm 2 , after 15 days of immersion, it dropped to 1.08×10 10 Ω cm 2 The impedance modulus of pure EP after immersion for 30 days (Z f=0.01Hz ) rapidly decreased to 2.64×10 9 Ω cm 2 , indicating that the corrosion particles have reached the substrate / coating interface and started to corrode the metal. As the immersion time continues to increase, the impedance modulus of pure EP decreases to 1.03×10 9 Ω cm 2 In view of the micro defects such as pores in the preparation process of pure EP coating, its resistance to electrolyte corrosion is difficult to meet the actual requirements of long-term use, so its anti-corrosion performance is limited. Compared with pure EP coating, composite coating containing CFs shows higher impedance value, such as Figure 6 Specifically, the impedance modulus (Z f=0.01Hz ) reached 8.08×10 after immersion for 5 days. 10 Ω cm 2, after 15 days of immersion, it was 3.90×10 10 Ω cm 2 And remain relatively stable. As time goes by, the impedance value decreases slightly. After 30 days of immersion, the low frequency (Z f=0.01Hz ) impedance value is 2.27×10 10 Ω cm 2 This indicates that the electrochemical process at the metal / coating interface is greatly suppressed and the composite coating has good protective performance. When the immersion time reaches 50 days, the low-frequency impedance value of the CFs@EP composite coating still remains at 1.39×10 10 Ω cm 2 From this, it can be inferred that the introduced CFs can significantly increase the anti-seepage performance of the coating and have long-term corrosion protection capabilities. The corrosion degree and damage process of the substrate can be reflected from the changes in the Bode phase angle diagram, such as Figure 6 As shown in a2 and b2 in Figure 1. The corrosion products produced at the interface between the metal substrate and the coating will destroy the interface bonding, reduce the adhesion of the coating, and cause the coating to peel off. Figure 6 As can be seen from a2 in Figure 1, with the increase of immersion time, the phase angle of the pure EP coating decreases significantly after 30 days. However, during the 50-day immersion process, the phase angle of the CFs@EP composite coating always remains at a high position. Figure 6 a3 and b3 in the figure are the Nernquist curves of pure EP and CFs@EP composite coatings after 50 days in 3.5wt.% NaCl solution. The size of the capacitance arc can roughly reflect the corrosion resistance of the coating. For pure EP coating, the capacitance arc decreases with the extension of immersion time, as shown in Figure 1. Figure 6 As shown in a3 in the figure, this indicates that the coating's corrosion protection against the metal is weakened. While the capacitive arc radius of the CFs@EP composite coating shows a decreasing trend compared to the pure EP coating, it is still an order of magnitude higher. These results further confirm that the CFs@EP composite coating possesses excellent long-term corrosion resistance.

[0059] Figure 7 These are optical photos of different samples in salt spray test. Figure 7 As shown in (a), after 30 days of testing, the common commercial coating showed obvious pitting and produced a lot of rust. As the test time increased to 60 days, corrosion rust accumulated in the damaged area of the coating and covered the surface of the sample. This is mainly attributed to the penetration and diffusion of corrosive ions into the coating matrix in the scratched area, indicating that its barrier performance is poor. Figure 7It can be observed in (b) that a small amount of white spots appeared on the pure EP coating after 30 days, and the coating color became lighter and accompanied by the aggregation of tiny white spots after 60 days, which indicates that water molecules have penetrated into the coating. However, 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, as shown in Figure 2. Figure 7 As shown in (b) of the figure, the densely arranged CFs effectively improve the barrier capacity of the coating, significantly enhance the anti-corrosion performance of the composite coating, and effectively improve the environmental adaptability of the carbon fiber reinforced resin-based composite coating in pipeline plugging.

[0060] The adhesion of pure EP coating and CFs@EP composite coating on carbon steel surface was tested by pull-out test. Figure 8 As can be seen from the figure, the bonding strength of the pure EP coating is 4.14 MPa, while that of the CFs@EP composite coating reaches a maximum of 17.95 MPa, a 3.3-fold increase compared to the pure EP coating. The densely packed CFs bind well to the resin, reducing voids in the coating matrix and enhancing the interfacial bonding strength between the resin and the coating. Furthermore, the CFs effectively enhance the coating's adhesion, giving the CFs@EP composite coating superior anti-corrosion properties.

[0061] The tensile tests of pure EP and CFs@EP composite coatings were carried out by a universal testing machine to evaluate the effect of CFs on the tensile strength of the coatings. Figure 9 The result is shown as a in Figure 9 As shown in Figures bd and c, the tensile strength of pure EP is 36.26 MPa, and the elongation at break is 98.58%. After the introduction of CFs, the tensile strength of the CFs@EP composite coating increased to 241.67 MPa, and the elongation at break reached 269.8%. Compared with the pure EP coating, the tensile strength and elongation at break of the CFs@EP composite coating increased by 5.7 times and 1.7 times, respectively. Analysis shows that the high toughness of CFs itself significantly contributes to the increased tensile strength of the composite coating. Furthermore, 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 significant advantages in the field of hot-plugging of oil and gas pipelines.

[0062] The cured epoxy resin itself is somewhat brittle, and the high cross-linking density results in poor crack propagation resistance of the coating, which limits its application in rapid pipeline plugging. In view of this, the impact resistance of pure EP coating and CFs@EP composite coating was evaluated by drop hammer impact test. The results are as follows: Figure 10 As shown. Figure 10As can be seen from a1, a2, b1, and b2 in Figure 1, when the impact hammer height is 30 cm, the pure EP coating shows obvious cracks that extend radially outward, with a length of about 8-10 mm. However, at the same drop hammer impact height, the surface of the CFs@EP composite coating remains unchanged. Further increasing the impact hammer height to 50 cm, the surface of the CFs@EP composite coating still shows no significant changes. Figure 10 When the impact hammer height is raised to 70 cm again, it can be observed that the center of the CFs@EP composite coating is slightly deformed but no cracks are generated. Figure 10 These results demonstrate that CFs significantly improve the brittleness of the cured coating and significantly enhance the impact resistance of the composite coating. The CFs@EP composite coating helps improve the mechanical damage protection of the pipeline after plugging.

[0063] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A carbon fiber reinforced resin-based composite coating, characterized in that: The invention comprises the following components by weight: 0.5-2 parts of carbon fiber, 3-5 parts of curing agent, 8-12 parts of epoxy resin, 1-1.5 parts of asphalt, 1-2 parts of diaminodiphenylmethane and 1-2 parts of glycidyl ether.

2. The carbon fiber reinforced resin-based composite coating according to claim 1, characterized in that: The carbon fiber includes carbon fiber cloth; Preferably, the curing agent is an amine curing agent, and the amine curing agent is one or more of a polyetheramine curing agent and an aliphatic amine curing agent, preferably a polyetheramine curing agent; the polyetheramine curing agent is one or more of D230, D400, T403, D2000 and T5000, preferably a polyetheramine D400 curing agent; Preferably, the epoxy resin is one or more of E51 resin and E44 resin, preferably E51 resin; Preferably, the glycidyl ether comprises glycerol triglycidyl ether.

3. A method for preparing a carbon fiber reinforced resin-based composite coating according to claim 1 or 2, characterized in that: The following steps are involved: impregnating the pretreated carbon fiber into a curing agent to obtain a curing agent mixture that impregnates the carbon fiber; mixing epoxy resin, asphalt, diaminodiphenylmethane and glycidyl ether, and mixing the mixture with the curing agent mixture impregnating the carbon fiber to obtain a resin mixture; The resin mixture is coated on the pre-treated substrate surface and cured at room temperature.

4. The preparation method according to claim 3, characterized in that The specific steps of pre-treating the carbon fiber include: immersing the carbon fiber in an acid solution, letting it stand, taking it out, and washing it; Preferably, the pH of the acid solution is 5-6; Preferably, the standing time is 6-12h; Preferably, the cleaning is performed by successively using water and anhydrous ethanol.

5. The preparation method according to claim 3, characterized in that Before pretreatment of carbon fiber, the carbon fiber needs to be cleaned and dried.

6. The preparation method according to claim 3, characterized in that The pretreated carbon fiber is immersed in the curing agent and needs to be left standing to be fully mixed, and the standing time is 1-3 hours.

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 to 10 minutes.

8. The preparation method according to claim 3, characterized in that The pretreatment of the substrate surface includes polishing, cleaning and drying the substrate surface. Preferably, the specific steps are polishing the substrate surface with sandpaper, cleaning it with acetone and ethanol through ultrasonic vibration, wiping it clean and drying it for later use.

9. Use of the carbon fiber reinforced resin-based composite coating according to claim 1 or 2 and / or the carbon fiber reinforced resin-based composite coating obtained by the preparation method according to any one of claims 3 to 8 in a pipeline; preferably, use in rapid sealing of a pipeline.

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

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