A temperature-resistant, corrosion-resistant and drag-reducing coating for the inner wall of a long-distance heat supply pipeline, a preparation method and application thereof

Abstract

This invention discloses a high-temperature resistant, corrosion-resistant, and drag-reducing coating for the inner wall of long-distance heating pipelines, its preparation method, and its application, belonging to the field of pipeline functional coating technology. The coating comprises a main agent A and an amine curing agent B. Main agent A uses modified epoxy resin and modified fluoropolymer as film-forming substances, combined with fillers such as talc and zinc phosphate, and specific functional additives, and is prepared through premixing, dispersion, shearing, and grinding. When sprayed onto the inner wall of long-distance heating pipelines, this coating forms a coating with a water contact angle of 113°, a surface roughness ≤2.27μm, a glass transition temperature Tg >130℃, and shows no significant corrosion after being boiled in 95℃ water for 900 days. Simultaneously, it reduces fluid friction resistance by 38.7% and transportation energy consumption by approximately 39%, effectively solving the problems of poor pipeline temperature resistance, high corrosion risk, and high resistance, extending pipeline life, and possessing both safety and energy-saving value.

Description

Technical Field

[0001] This invention relates to the field of pipeline functional coatings, and in particular to a temperature-resistant, corrosion-resistant, and drag-reducing coating for the inner wall of long-distance heating pipelines, its preparation method, and its application. Background Technology

[0002] With the acceleration of urbanization, centralized heating has become the main method of heating in large cities. Long-distance heating pipelines, as the "main arteries" of energy transportation, are of paramount importance in terms of operational safety and economy. However, existing heating network technologies face the following three core problems in actual operation: (1) Internal corrosion and safety hazards: At present, the inner surface of most heating pipes is "bare pipe" and lacks effective internal protective coating. As the service life of the heating network increases, the pipes are exposed to high temperature heat medium for a long time, and the inner surface gradually corrodes, resulting in thinning of the pipe wall and perforation. This not only leads to the actual service life of the pipe being far less than the 30-year design life, but also easily causes safety accidents such as pipe bursts, bringing huge safety risks and economic losses to heating companies.

[0003] (2) Fluid resistance and energy consumption issues: The roughness of the inner surface of the bare pipe of large-diameter (DN1000 and above) and long-distance (tens of kilometers) heating pipelines is high, which directly deteriorates the fluid flow conditions and leads to a significant increase in frictional resistance along the pipeline. Moreover, the high roughness surface is also prone to scaling during long-term operation, which further increases the resistance and reduces the heat transfer efficiency of the heat exchanger. Therefore, the heat source plant needs to maintain a higher transmission pressure, resulting in huge pumping power consumption.

[0004] (3) Limitations of existing technology: Most anti-corrosion coatings on the market cannot simultaneously meet the dual requirements of "high temperature resistance (long-term resistance to 130℃ hot water)" and "high efficiency drag reduction (extremely low surface energy)". Ordinary epoxy coatings are prone to failure under high temperature water immersion, and have limited hydrophobic properties (contact angle is far below 100°), and the drag reduction effect is not obvious.

[0005] Therefore, developing coatings that combine high-temperature corrosion resistance and high-efficiency drag reduction properties is of great significance for ensuring the long-term safe operation of long-distance heating pipelines and achieving low-carbon energy conservation. Summary of the Invention

[0006] The purpose of this invention is to provide a high-temperature resistant, corrosion-resistant, and drag-reducing coating for the inner wall of long-distance heating pipelines, its preparation method, and its application, to solve the problems of poor temperature resistance, high corrosion risk, and high transport resistance of existing long-distance heating pipeline inner walls, and to achieve the synergistic performance of high temperature resistance, corrosion resistance, and efficient drag reduction of the coating.

[0007] To achieve the above objectives, the present invention provides a temperature-resistant, corrosion-resistant, and drag-reducing coating for the inner wall of long-distance heating pipelines, comprising a main agent A and an amine curing agent B; wherein, by weight percentage, the main agent A comprises the following raw materials: Film-forming substances: 10-20% modified epoxy resin, 10-20% modified fluoropolymer; Filler: 15-25% talc, 8-20% zinc phosphate; Functional additives: defoamer 0.4~0.8%, dispersant 0.4~0.8%, rheology modifier 0.3~0.8%, anti-settling agent bentonite 0.8~1.5%; Solvent: Balance.

[0008] Preferably, the defoamer is BYK052, the dispersant is BYK163, the rheology modifier is PM1510, and the antisettling agent is bentonite SD-2.

[0009] Preferably, the solvent is a mixture of xylene and n-butanol.

[0010] Preferably, the amine curing agent B is phenolic amine T-31.

[0011] This invention also provides a method for preparing the above-mentioned high-temperature resistant, corrosion-resistant, and drag-reducing coating for the inner wall of a long-distance heating pipeline, comprising the following steps: S1. Film-forming materials are prepared by toughening modification with elastomers, toughening modification with thermoplastics, and composite modification with inorganic nanoparticles. S2. Resin Dissolution and Premixing: The solvent, modified epoxy resin and modified fluoropolymer are stirred and premixed to form a homogeneous base material; S3. Dispersion of functional additives: Add dispersant, defoamer, leveling agent and rheology modifier in sequence, and stir to disperse evenly; S4. High-speed shear dispersion of thixotropic agents: Add anti-settling agent for high-speed shear dispersion; S5. Filler mixing and dispersion: Add talc and zinc phosphate, stir and disperse to obtain a mixed slurry; S6. Grinding and refining: Grind the mixed slurry to a fineness of ≤60μm to obtain main agent A. Mix main agent A with amine curing agent B evenly to obtain the target coating.

[0012] Preferably, in step S6, the mass ratio of main agent A to amine curing agent B is 10:1.

[0013] The present invention also provides the application of the above-mentioned temperature-resistant, corrosion-resistant, and drag-reducing coating for the inner wall of a long-distance heating pipeline. The coating is used for spraying onto the inner wall of the long-distance heating pipeline and forms a protective coating after curing.

[0014] Preferably, the inner wall of the long-distance heating pipeline is pretreated by steel shot blasting, and the surface roughness meets the Sa2.5 level.

[0015] Preferably, the dry film thickness of the protective coating is 400-500 μm.

[0016] Preferably, the water contact angle of the protective coating is 113°, the glass transition temperature Tg is greater than 130°C, and the surface roughness is less than 2.27 μm.

[0017] Therefore, the high-temperature resistant, corrosion-resistant, and drag-reducing coating for the inner wall of long-distance heating pipelines provided by this invention, its preparation method, and its application have the following beneficial effects: (1) Excellent drag reduction characteristics: The water contact angle of the sprayed coating reaches 113° and the surface roughness is only 2.27μm, which is about 97% lower than that of the bare pipe, and the fluid friction resistance is reduced by 38.7%.

[0018] (2) Excellent temperature resistance and corrosion resistance: the glass transition temperature Tg>130℃, no obvious corrosion after boiling in water at 95℃ for 900 days, and the surface roughness only increases to 8.52μm, which is much lower than the 72μm after the bare tube is corroded.

[0019] (3) Significant energy-saving benefits: Actual engineering measurements show that the energy consumption of the entire long-distance heating pipeline is reduced by about 39%, and energy consumption can be saved by about 1928.8 MWh in a single heating season (121 days), demonstrating outstanding low-carbon and energy-saving effects.

[0020] (4) Extend pipeline life: effectively block the corrosion of the pipe wall by high temperature heat medium, avoid thinning and perforation of the pipe wall, extend the service life of the pipeline, and reduce the safety risks and economic losses of heating companies.

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] Figure 1 The figures show a comparison of water droplet contact angle tests on different coating surfaces in the embodiments and comparative examples of the present invention; where (a) is Comparative Example 1; (b) is Comparative Example 2; and (c) is Example 1. Figure 2 This is a DSC curve of the coating in Embodiment 1 of the present invention; Figure 3 This is a comparison diagram of the operating pressure difference between the pipe coated with the coating of Example 1 of the present invention and the uncoated pipe of Comparative Example 1 during the heating season; wherein, (a) is the water supply pipe and (b) is the return water pipe. Figure 4 A comparison chart of transport energy consumption between the coated pipe of Example 1 of the present invention and the uncoated pipe of Comparative Example 1. Detailed Implementation

[0023] This invention provides a temperature-resistant, corrosion-resistant, and drag-reducing coating for the inner wall of long-distance heating pipelines, comprising a main agent A and an amine curing agent B; wherein, by weight percentage, the main agent A comprises the following raw materials: Film-forming substances: 10-20% modified epoxy resin and 10-20% modified fluoropolymer. The coating is endowed with excellent temperature resistance and hydrophobicity through organic-inorganic hybrid modification.

[0024] Fillers: 15-25% talc powder and 8-20% zinc phosphate, to improve the density and corrosion resistance of the coating.

[0025] Functional additives: defoamer 0.4~0.8% (BYK052), dispersant 0.4~0.8% (BYK163), rheology modifier 0.3~0.8% (PM1510), and anti-settling agent 0.8~1.5% (bentonite SD-2), which respectively achieve the functions of defoaming, dispersing, leveling and anti-settling.

[0026] Solvent: The balance is a mixture of xylene and n-butanol, used to adjust the viscosity of the coating during application.

[0027] Amine curing agent B: Phenolic amine T-31 is mixed with main agent A at a mass ratio of 10:1 to achieve curing.

[0028] This invention also provides a method for preparing the above-mentioned temperature-resistant and drag-reducing coating: S1. Film-forming materials are prepared by toughening modification with elastomers, toughening modification with thermoplastics, and composite modification with inorganic nanoparticles.

[0029] S2. Resin Dissolution and Premixing: Take the solvent, modified epoxy resin and modified fluoropolymer, and stir at a low speed of 90-120 r / min to premix and form a homogeneous base material.

[0030] S3. Dispersion of functional additives: Add dispersant, defoamer, leveling agent and rheology modifier in sequence, and stir at 120-150 r / min for 5-10 min to disperse, ensuring that the additives fully wet the resin system, eliminate bubbles and improve leveling.

[0031] S4. High-speed shearing of thixotropic agent: Add anti-settling agent and shear at 120-300 r / min for 10-15 min to activate the thixotropic structure, prevent the subsequent addition of heavy fillers from settling, and ensure the storage stability of the coating.

[0032] S5. Filler mixing and dispersion: Add talc powder and zinc phosphate, stir and disperse at a stirring speed of 120-150 r / min for 20 minutes to fully coat and wet the filler, and obtain a mixed slurry.

[0033] S6. Grinding and refining: The mixed slurry is fed into a conical grinder for grinding until the fineness is ≤60μm to obtain the main agent A. The main agent A is then mixed evenly with the amine curing agent B to obtain the target coating.

[0034] The present invention also provides the application of the above-mentioned coating using a high-pressure airless spraying device for spraying the inner wall of a long-distance heating pipeline (surface roughness meets Sa2.5 level), and forming a protective coating after curing, with the dry film thickness controlled at 400-500μm.

[0035] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention. Furthermore, it should be understood that after reading the contents 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 by the appended claims and are all within the protection scope of the present invention.

[0036] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0037] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0038] Unless otherwise specified, the reagents, instruments, and equipment used in this invention are all commonly used by those skilled in the art, and the testing standards all use national or international standards commonly used in the field, without further explanation.

[0039] Example 1 This embodiment provides a temperature-resistant, corrosion-resistant, and drag-reducing coating for the inner wall of a long-distance heating pipeline, comprising a main agent A and an amine curing agent B; wherein, by weight percentage, the main agent A comprises the following raw materials: Film-forming substances: 16% modified epoxy resin and 14% modified fluoropolymer.

[0040] Filler: 22% talc, 12% zinc phosphate.

[0041] Functional additives: defoamer BYK052 0.5%, dispersant BYK163 0.6%, rheology modifier PM1510 0.4%, antisettling agent bentonite SD-2 1.0%.

[0042] Solvent: Xylene and n-butanol are mixed in a volume ratio of 1:1, with the remainder being 33.5%.

[0043] Amine curing agent B: Phenolic amine T-31, mixed with main agent A at a mass ratio of 10:1.

[0044] The preparation of this coating includes the following steps: S1. Select 100 parts of bisphenol A type epoxy resin (E-51), 15 parts of carboxyl-terminated liquid nitrile rubber (CTBN), and 0.3 parts of triphenylphosphine (catalyst); heat the epoxy resin to 80°C, add CTBN, and stir for 10 minutes; raise the temperature to 120°C, add triphenylphosphine, and react for 1.5 hours; cool down to 60°C, discharge the material, and obtain CTBN modified epoxy resin.

[0045] Select 100 parts of polyvinylidene fluoride (PVDF), 5 parts of nano-SiO2 (hydrophobic treated, particle size 20nm), 1 part of silane coupling agent (KH-570), and 200 parts of N,N-dimethylacetamide (DMAc); disperse nano-SiO2 and KH-570 in DMAc and sonicate for 30 minutes; add PVDF powder and stir at high speed until completely dissolved; heat to 80℃ and react for 2 hours to graft nanoparticles onto polymer chains; after cooling, discharge to obtain nano-SiO2 modified PVDF.

[0046] S2. Resin Dissolution and Premixing: Pour 33.5% of the mixed solvent into the sample preparation tank of the high-speed disperser, add 16% of modified epoxy resin and 14% of modified fluoropolymer in sequence, adjust the stirring speed to 120 r / min, and premix at low speed for 15 minutes to completely dissolve the resin and form a uniform and transparent base material.

[0047] S3. Dispersion of functional additives: Keep the stirring speed at 120 r / min, and add 0.6% dispersant BYK163, 0.5% defoamer BYK052, 0.3% leveling agent BYK358N and 0.4% rheology modifier PM1510 in sequence. Continue to disperse for 8 minutes to ensure that the additives are evenly dispersed in the base material, eliminate air bubbles in the system and optimize the leveling performance.

[0048] S4. High-speed shearing with thixotropic agent: Add 1.0% bentonite SD-2 anti-settling agent to the system, increase the speed of the disperser to 120 r / min, and perform high-speed shearing dispersion for 12 minutes to activate the thixotropic network structure of bentonite and prevent subsequent filler settling.

[0049] S5. Filler mixing and dispersion: Maintain a stirring speed of 120 r / min, first add 22% talc powder, disperse for 10 minutes, then add 12% zinc phosphate, and continue to disperse for 20 minutes to ensure that the filler particles are fully coated and wetted by the base material to form a uniform mixed slurry.

[0050] S6. Grinding and refining: Transfer the mixed slurry into a conical grinder, adjust the grinding gap to 0.05mm, and grind 3 times until the fineness of the coating reaches 55μm to obtain the main agent A. Mix the main agent A with the amine curing agent B, stir evenly, and let it stand for 15 minutes to mature and obtain an applicable coating.

[0051] For pipeline construction, a DN1600 carbon steel long-distance heating pipeline section was selected. First, the inner wall was pre-treated by steel shot blasting at a controlled pressure of 0.6 MPa. After treatment, the surface roughness of the inner wall met Sa2.5 grade (surface roughness Ra = 40~70 μm). Then, a high-pressure airless spraying device was used to uniformly spray the cured finished coating onto the inner wall of the pipeline at a controlled pressure of 15 MPa. The dry film thickness of a single spray was 200~250 μm, and the coating was applied in two coats, resulting in a final dry film thickness of 480 μm. After spraying, the coating was cured at room temperature for 7 days at 25℃ and 60% relative humidity to form a complete protective coating.

[0052] Comparative Example 1 This comparative example provides a bare pipe for a long-distance heating pipeline. The bare pipe is the same as the pipe used in Example 1. Both are selected as DN1600 carbon steel long-distance heating pipeline sections. The inner wall is pretreated by steel shot blasting with a controlled blasting pressure of 0.6MPa. After treatment, the surface roughness of the inner wall of the pipeline meets the Sa2.5 grade.

[0053] Comparative Example 2 This comparative example provides a long-distance heating pipeline coated with a common epoxy coating. This pipeline is the same as the one used in Example 1, both being DN1600 carbon steel long-distance heating pipeline sections. The inner wall was first pre-treated by shot blasting at a controlled pressure of 0.6 MPa, resulting in a surface roughness of Sa2.5. A high-pressure airless spraying device was then used to uniformly spray the common epoxy coating Protal 7200 onto the inner wall of the pipeline. After curing, a complete common epoxy protective coating was formed.

[0054] To verify the performance of the temperature-resistant and drag-reducing coatings prepared in the above embodiments, the pipes of the embodiments and comparative examples 1-2 were tested and analyzed.

[0055] 1. Surface wettability and contact angle test: The water droplet contact angle of the pipe coating was tested using a Kruss DSA100 contact angle meter, and the results are as follows: Figure 1 As shown.

[0056] Depend on Figure 1 It can be seen that the water droplets on the surface of the coating formed by spraying the paint prepared in the embodiments of the present invention are obviously spherical. Figure 1(c) The contact angle reaches 113°, which is very close to the contact angle of polytetrafluoroethylene (PTFE), a recognized excellent hydrophobic material (115.8°), and much higher than that of the bare tube in Comparative Example 1 (contact angle of 45°). Figure 1 (a) and the ordinary epoxy coating of Comparative Example 2 (contact angle 82°, Figure 1 (b) proves that the coating formed by spraying the coating prepared by the present invention has excellent hydrophobicity and is difficult to wet with water, which provides a physical basis for the "slippage" of fluid at the pipe wall, i.e. drag reduction performance.

[0057] 2. Surface roughness and aging resistance test: The inner wall surface of the pipe under the following three conditions was tested at multiple points using a roughness tester (model TR200), and the average value was taken: (A) bare pipe after corrosion; (B) surface freshly coated with the coating of this invention; (C) coated surface after being boiled in water at 95°C for 900 days. Data comparison: (A) Roughness of bare corroded pipe: 72μm; (B) Roughness of the newly applied coating: 2.27 μm; (C) Aging coating roughness: 8.52μm.

[0058] The coating formed by the paint in this embodiment of the invention not only has extremely high initial smoothness (roughness reduced by about 97%), but also, after being immersed in high-temperature water for up to 900 days, although the roughness increases slightly, it is still far lower than that of the bare pipe. This proves that the coating can block the corrosion of high-temperature water media for a long time, avoiding the formation of "pits" and "dents" on the pipe wall due to corrosion, thereby maintaining a low resistance state for a long time.

[0059] 3. Temperature stability test: The thermal properties of the coating formed by the paint in Example 1 were analyzed using a differential scanning calorimeter (DSC, model Q2000). The heating rate was 10℃ / min, and the atmosphere was nitrogen. The results are as follows: Figure 2 As shown.

[0060] Depend on Figure 2 It is known that the glass transition temperature Tg of the coating is greater than 130℃. This is due to the FC bond, the rigid structure of the benzene ring and the Si-C bond introduced by the modified fluoropolymer in the formula, which endow the coating with excellent thermal stability and fully meet the design and operation requirements of 130℃ for heating pipe networks.

[0061] 4. Engineering application verification: The coating prepared in Example 1 was applied to the Dengfeng to Zhengzhou long-distance heating pipeline project (pipeline diameter DN1600, single-trip length 65km, design water supply temperature 130℃, operating pressure 2.5MPa, direct burial). A 10km section was selected as the test section, and the remaining uncoated sections were used as the control section. Operational data for the entire heating season (121 days) were collected.

[0062] (1) Pressure difference comparison: such as Figure 3 As shown, at the same conveying flow rate (800m³ / h) 3 / h) below, the water supply pipe with coating ( Figure 3 (a) and return pipe ( Figure 3 (b) The operating pressure difference was reduced by 37.2% and 40.1% respectively compared with the control section, and the average pressure difference was reduced by 38.7%, which directly confirms the drag reduction effect of the coating.

[0063] (2) Energy consumption comparison: By monitoring the operating power of the heat source plant's transfer pumps, the energy consumption of the entire transfer line was calculated, and the results are as follows: Figure 4 As shown, by Figure 4 It can be seen that the total energy consumption of the coated pipe section during the entire heating season was 2971.2 MWh, which is 1908.8 MWh less than the 4880.0 MWh of the control section. The overall energy consumption of transmission and distribution was reduced by 39%, and the energy-saving benefits were significant.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A temperature-resistant, corrosion-resistant, and drag-reducing coating for the inner wall of a long-distance heating pipeline, characterized in that, It includes main agent A and amine curing agent B; wherein, by weight percentage, main agent A includes the following raw materials: Film-forming substances: 10-20% modified epoxy resin, 10-20% modified fluoropolymer; Filler: 15-25% talc, 8-20% zinc phosphate; Functional additives: defoamer 0.4~0.8%, dispersant 0.4~0.8%, rheology modifier 0.3~0.8%, anti-settling agent bentonite 0.8~1.5%; Solvent: Balance.

2. The high-temperature resistant, corrosion-resistant, and drag-reducing coating for the inner wall of a long-distance heating pipeline according to claim 1, characterized in that, The defoamer is BYK052, the dispersant is BYK163, the rheology modifier is PM1510, and the anti-settling agent is bentonite SD-2.

3. The high-temperature resistant, corrosion-resistant, and drag-reducing coating for the inner wall of a long-distance heating pipeline according to claim 1, characterized in that, The solvent is a mixture of xylene and n-butanol.

4. The high-temperature resistant, corrosion-resistant, and drag-reducing coating for the inner wall of a long-distance heating pipeline according to claim 1, characterized in that, Amine curing agent B is phenolic amine T-31.

5. A method for preparing a temperature-resistant, corrosion-resistant, and drag-reducing coating for the inner wall of a long-distance heating pipeline as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Film-forming materials are prepared by toughening modification with elastomers, toughening modification with thermoplastics, and composite modification with inorganic nanoparticles. S2. Resin Dissolution and Premixing: The solvent, modified epoxy resin and modified fluoropolymer are stirred and premixed to form a homogeneous base material; S3. Dispersion of functional additives: Add dispersant, defoamer, leveling agent and rheology modifier in sequence, and stir to disperse evenly; S4. High-speed shear dispersion of thixotropic agents: Add anti-settling agent for high-speed shear dispersion; S5. Filler mixing and dispersion: Add talc and zinc phosphate, stir and disperse to obtain a mixed slurry; S6. Grinding and refining: Grind the mixed slurry to a fineness of ≤60μm to obtain main agent A. Mix main agent A with amine curing agent B evenly to obtain the target coating.

6. The method for preparing a temperature-resistant, corrosion-resistant, and drag-reducing coating for the inner wall of a long-distance heating pipeline according to claim 5, characterized in that, In step S6, the mass ratio of main agent A to amine curing agent B is 10:

1.

7. The application of a temperature-resistant, corrosion-resistant, and drag-reducing coating for the inner wall of a long-distance heating pipeline as described in any one of claims 1-4, characterized in that, The coating is used for spraying the inner wall of long-distance heating pipelines, and forms a protective coating after curing.

8. The application of a temperature-resistant, corrosion-resistant, and drag-reducing coating for the inner wall of a long-distance heating pipeline according to claim 7, characterized in that, The inner wall of the long-distance heating pipeline is pretreated by steel shot blasting, and the surface roughness meets the Sa2.5 grade.

9. The application of a temperature-resistant, corrosion-resistant, and drag-reducing coating for the inner wall of a long-distance heating pipeline according to claim 7, characterized in that, The dry film thickness of the protective coating is 400-500μm.

10. The application of a temperature-resistant, corrosion-resistant, and drag-reducing coating for the inner wall of a long-distance heating pipeline according to claim 7, characterized in that, The protective coating has a water contact angle of 113°, a glass transition temperature Tg > 130℃, and a surface roughness ≤ 2.27μm.

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