Process for preparing long-acting oleophobic coating of pipeline based on chemical vapor deposition

Abstract

The invention relates to the technical field of pipeline surface treatment, and discloses a pipeline long-acting oleophobic coating preparation process based on chemical vapor deposition, which comprises the following steps: cleaning and drying a to-be-prepared pipeline, and putting the pipeline into a customized cylindrical vacuum chamber; the cylindrical vacuum chamber is pre-vacuumized to the pressure Pa, and then mixed gas of high-purity oxygen and argon is introduced into the cylindrical vacuum chamber; and starting a radio frequency plasma generator to perform plasma activation on the mixed gas in the cylindrical vacuum chamber and the inner or outer surface of the pipeline. The problems that the inner wall coating is thicker when being closer to a pipeline opening and is thinner when being closer to the center of the pipeline are solved, so that the growth speed of the inner wall center coating is greatly increased, the inner wall thickness uniformity is ensured, and the problem of the thickness difference between the end opening and the center coating caused by insufficient particle diffusion in the traditional process is thoroughly solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pipeline surface treatment, and in particular to a long-acting oil-repellent coating preparation process for pipelines based on chemical vapor deposition. BACKGROUND

[0002] In the field of gas pipeline preparation, the surface of the gas pipeline is prone to contamination with domestic oil, and the inner wall of the pipeline is prone to contamination with chemical oil gas in the gas, so it is crucial to prepare an oil-repellent coating on the inner and outer surfaces of the gas pipeline.

[0003] When the conventional method is used to prepare an oil-repellent coating on the surface of a pipeline, each orientation of the outer surface of the pipeline can effectively contact the plating particles, and the oil-repellent coating formed at this time is relatively uniform (as shown in A of Figure 2 However, when the oil-repellent coating is prepared on the inner wall of the pipeline, the plating particles diffuse into the interior through the port of the pipeline, and the oil-repellent coating is formed in the region close to the port first, while it is difficult to form an oil-repellent coating in the region far from the port (as shown in B of Figure 2 At this time, the problem of uneven distribution of the oil-repellent coating is caused.

[0004] Chemical vapor deposition is a chemical technology that mainly uses one or more gas-phase compounds or elements containing thin film elements to generate a thin film on the surface of a substrate through a chemical reaction. Chemical vapor deposition is a new technology for preparing inorganic materials that has developed in recent decades. Chemical vapor deposition has been widely used for purifying substances, developing new crystals, depositing various single-crystal, polycrystalline or glassy inorganic thin film materials.

[0005] The existing patent discloses a preparation method of a corrosion-resistant structure of a petroleum stainless steel pipeline (publication number CN110468437A). In the technology disclosed in the existing patent, an electrodeposition process is used, which relies on the flowability of the electrolyte and the electrode layout. For the inner wall of the pipeline (especially long pipelines), the electrolyte cannot uniformly penetrate to the central region, resulting in a coating thickness decay of more than 70% from the port to the center. SUMMARY

[0006] The present application provides a long-acting oil-repellent coating preparation process for pipelines based on chemical vapor deposition to solve the existing technical problems, and solves the problem of uneven preparation of the oil-repellent coating on the inner wall of the pipeline.

[0007] To solve the above technical problems, according to one aspect of the present application, more specifically, a long-acting oil-repellent coating preparation process for pipelines based on chemical vapor deposition, comprising the following steps:

[0008] S1, after cleaning and drying the pipeline to be prepared, placing it in a customized cylindrical vacuum chamber;

[0009] S2, the cylindrical vacuum chamber is pre-evacuated to a pressure Pa, and then a mixture of high-purity oxygen and argon gas is introduced into the cylindrical vacuum chamber.

[0010] S3, the radio frequency plasma generator is turned on to plasma-activate the mixture of gases in the cylindrical vacuum chamber and the inner or outer surface of the pipeline.

[0011] The radio frequency plasma generator is a device that ionizes gas through a radio frequency electric field (13.56 MHz) to generate plasma containing ions, electrons, and free radicals.

[0012] Its role is to activate the surface of the pipeline (implant hydroxyl), strip contaminants (argon ion bombardment), and enhance the adhesion of the coating.

[0013] S4, the radio frequency plasma generator is turned off and argon gas is introduced for 5 minutes for passivation cooling, and then the passivated and cooled pipeline is placed in a double-walled quartz tube furnace.

[0014] S5, a precursor evaporation system is used to vaporize a premixed solution of tetraethyl orthosilicate and ethanol to form a precursor, and the precursor is carried into the double-walled quartz tube furnace by a mixture of nitrogen and argon gas.

[0015] S6, the size of the coating particles on the surface of the pipeline is controlled by controlling the ratio of nitrogen and argon.

[0016] S7, a microwave interference system is used to perform microwave interference on the inner surface of the pipeline to increase the growth rate of coating particles at the center of the inner surface of the pipeline.

[0017] S8, the pipeline after deposition of the coating particles is transferred to a CVD reaction chamber and evacuated to a pressure Pa, and then dry nitrogen gas is introduced for 10 minutes to remove residual volatile substances.

[0018] S9, fluorosilane is placed in a constant-temperature vaporization chamber controlled at a temperature of 80-100°C, and high-purity nitrogen or argon gas is introduced as a carrier gas at a flow rate of 10-20 sccm to carry the fluorosilane vapor into the CVD reaction chamber.

[0019] Further, in step S2, the volume ratio of oxygen to argon is 3:1, and the total flow rate of the mixture of high-purity oxygen and argon gas introduced into the cylindrical vacuum chamber is 70 sccm; the adsorbed contaminants are stripped by argon ion bombardment in the argon gas, and active oxygen species are generated by oxygen ionization.

[0020] Further, in step S3, the frequency of the radio frequency plasma generator is 13.56 MHz, the working power ranges from 300 W to 500 W, and the duration is 10-20 minutes.

[0021] Furthermore, in step S5, the precursor evaporation system includes a temperature-controlled flash tank set at 80-90°C to vaporize tetraethyl orthosilicate and ethanol in a volume ratio of 1:10.

[0022] Furthermore, the microwave interferometer system includes a microwave transmitter A and an intermediate diffraction layer;

[0023] The microwave transmitter A is used to transmit sinusoidal microwaves with a frequency of 2.45 GHz and a power of 400 W–600 W into the intermediate diffraction layer;

[0024] The intermediate diffraction layer includes diffraction gratings A1 and A2.

[0025] Furthermore, the microwaves generated by the microwave transmitter A enter the diffraction gratings A1 and A2 and generate new sinusoidal microwaves respectively. The superposition region of the two new sinusoidal microwaves is located in the middle region of the pipe.

[0026] Furthermore, when preparing a coating on the outer surface of the pipe, after controlling particle growth in step S6, it directly enters the CVD reaction chamber in step S8.

[0027] When preparing a coating on the inner surface of the pipe, step S7 is required to use a microwave interference system to perform microwave interference on the inner surface of the pipe.

[0028] Furthermore, the fluorosilane is perfluorooctyltrichlorosilane, and the fluorosilane vapor is deposited in the CVD reaction chamber at a temperature of 120-150°C, a pressure of 20-50 Pa, and a deposition time of 50-70 minutes to form a covalently bonded Si-O-Si-F low surface energy layer.

[0029] The chemical vapor deposition-based pipeline long-lasting oleophobic coating preparation process provided by this invention offers the following advantages compared to existing technologies:

[0030] 1. This invention solves the problem that the inner wall coating is thicker closer to the pipe opening and thinner closer to the center of the pipe. This greatly increases the growth rate of the coating in the center of the inner wall, thereby ensuring uniform inner wall thickness and completely solving the difference in coating thickness between the port and the center caused by insufficient particle diffusion in traditional processes.

[0031] 2. This invention combines in-situ generated coating particles from the sol-gel method with fumed fluorosilane modification to form a micro-nano rough structure and low surface energy fluorocarbon chain. The coating has a water contact angle >150° and an oil contact angle >140°. After 500 wear tests, it still maintains a hydrophobicity of >130°, significantly reducing the oil adhesion rate.

[0032] 3. This invention uses oxygen plasma to activate and implant high-density hydroxyl groups, which enables the coating particle layer to form a strong bond with the substrate; fluorosilane is anchored to the surface of the coating particles through Si-O-Si-F covalent bonds, achieving an adhesion level of ISO2409 standard 0. After salt spray corrosion, the contact angle decreases, making it suitable for high-temperature and highly corrosive oil and gas environments.

[0033] 4. The entire process of this invention adopts CVD technology, with no solvent emissions and significantly reduced energy consumption; microwave interference technology compresses the coating time of the inner wall to 105 minutes and the coating of the outer wall to only 85 minutes, and is compatible with complex pipeline structures, extending the cleaning cycle by 3-5 times, and greatly reducing the risk of fire caused by corrosion of gas pipelines. Attached Figure Description

[0034] Figure 1 This is a flowchart of the present invention;

[0035] Figure 2 In the diagram, A represents a schematic diagram of coating preparation on the outer surface of the pipe. Figure 2 In the diagram, B represents a schematic diagram of coating preparation on the inner surface of the inner pipe;

[0036] Figure 3 This is a schematic diagram of the microwave interferometry system in this invention;

[0037] Figure 4 This is a flowchart of the coating preparation process for the outer surface of the pipe in this invention;

[0038] Figure 5 This is a flowchart of the coating preparation process for the inner surface of the pipe in this invention. Detailed Implementation

[0039] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] Example 1

[0041] like Figure 2 A in and Figure 4 As shown, the preparation of a long-lasting oleophobic coating on the outer surface of a gas pipeline includes the following steps:

[0042] Preprocessing (Steps 1-4):

[0043] Step 1: After cleaning and drying the pipe to be prepared, place it into a custom-made cylindrical vacuum chamber;

[0044] Step 2: Pre-evacuate the cylindrical vacuum chamber to the required pressure. Pa, then a mixture of high-purity oxygen and argon is introduced into the cylindrical vacuum chamber;

[0045] In this step, the volume ratio of oxygen to argon is 3:1, and the total flow rate of the mixture of high-purity oxygen and argon injected into the cylindrical vacuum chamber is 70 sccm; pollutants are adsorbed by bombardment with argon ions in the argon gas, and active oxygen species are generated by oxygen ionization.

[0046] Step 3: Turn on the radio frequency plasma generator to activate the mixed gas in the cylindrical vacuum chamber and the inner or outer surface of the pipes with plasma.

[0047] Mixed gas It ionizes to generate reactive oxygen free radicals, which oxidize surface contaminants.

[0048] In this step, the frequency of the radio frequency plasma generator is 13.56MHz, the operating power is 400W (optimal), and the duration is 15 minutes.

[0049] Step 4: Turn off the radio frequency plasma generator and passivate the tube by introducing argon gas for 5 minutes. Then, place the passivated and cooled tube into a double-walled quartz tube furnace.

[0050] Argon ion bombardment strips away the micro-adsorption layer, implanting hydroxyl groups at a density of up to [missing information]. groups / cm² (XPS verification).

[0051] Hydroxyl density ( (groups / cm²) represents the number of hydroxyl groups (-OH) per unit area of ​​surface area, quantitatively determined by XPS (X-ray photoelectron spectroscopy). Hydroxyl density indicates the increase in the number of hydroxyl groups per unit area. The chemical bonding strength between nanoparticles and the substrate ensures grade 0 adhesion of the coating.

[0052] The preprocessing can be summarized as follows:

[0053] Pipeline cleaning: Use ethanol for ultrasonic cleaning for 15 minutes to remove grease and particulate matter.

[0054] Plasma activation: RF power 400W (optimal value), time 15min;

[0055] Mixed gas It ionizes to generate reactive oxygen free radicals, which oxidize surface contaminants;

[0056] Argon ion bombardment strips away the micro-adsorption layer, implanting hydroxyl groups at a density of up to [missing information]. groups / cm² (XPS verification).

[0057] Coating particle deposition (steps five and six):

[0058] Step 5: Use a precursor evaporation system to vaporize the premixed liquid of tetraethyl orthosilicate and ethanol to form a precursor, and inject the precursor into a double-walled quartz tube furnace by a mixed gas of nitrogen and argon.

[0059] In this step, the precursor evaporation system includes a temperature-controlled flash tank set at 85°C to vaporize tetraethyl orthosilicate and ethanol in a volume ratio of 1:10.

[0060] Step Six: Adjust the surface temperature of the pipeline by controlling the ratio of nitrogen to argon. Coating particle growth size;

[0061] The summary of coating particle deposition is as follows:

[0062] Ethyl orthosilicate / ethanol premix (1:10) was vaporized in an 85°C flash evaporator and carried by a nitrogen / argon mixture (1:1 ratio);

[0063] The double-walled quartz furnace was set at 180℃ and 80Pa for 40 minutes.

[0064] Particle size control: Increasing the argon ratio and decreasing the particle size (argon gas inhibits the hydrolysis rate of tetraethyl orthosilicate) yielded a uniform particle size of 200±50 nm. Nanoparticles (SEM verification).

[0065] Fluorosilane modification (steps seven to eight):

[0066] Step 7: Deposit The coated particles are transferred to the CVD reaction chamber and evacuated to pressure. Pa, then flush with dry nitrogen for 10 minutes to remove residual volatile substances;

[0067] Step 8: Place the fluorosilane in a constant temperature vaporization chamber (100°C) and introduce high-purity nitrogen or argon as a carrier gas. The carrier gas flow rate is 10–20 sccm to carry the fluorosilane vapor into the CVD reaction chamber.

[0068] The fluorosilane is perfluorooctyltrichlorosilane. The deposition temperature of the fluorosilane vapor in the CVD reaction chamber is 120-150℃, the pressure is 20-50Pa, and the deposition time is 50-70 minutes, forming a covalently bonded Si-O-Si-F low surface energy layer.

[0069] The summary of fluorosilane modification is as follows:

[0070] Perfluorooctyltrichlorosilane is vaporized in a vaporization chamber at 100°C and carried to the CVD reaction chamber by a nitrogen carrier gas (15 sccm).

[0071] Deposition parameters: 130℃, 35Pa, 60min, forming Si-O-Si-F covalent bonds (FTIR detection at 1105 cm⁻¹). Characteristic peaks); Si-O-Si-F covalent bonds represent fluorosilanes (PFOTS) and... The product of the surface hydroxyl reaction.

[0072] Surface fluorocarbon chain coverage ≥98% (XPS-F1s peak intensity ratio. The XPS-F1s peak intensity ratio is the percentage of fluorine signal intensity in X-ray photoelectron spectroscopy ≥98%, indicating fluorocarbon chain coverage). Complete surface coverage to achieve superoleophobicity.

[0073] Summary of the technical content and effects of the above steps:

[0074] The specific technical content of ion activation in step three is: radio frequency power 400W. The mixed gas is activated for 15 minutes. The effect of step three is that argon ion bombardment removes microscopic contaminants, and reactive oxygen free radicals are implanted into high-density hydroxyl groups. groups / cm², significantly improving coating adhesion (ISO2409 Class 0).

[0075] The specific technical content of particle size control in step six is: adjustment The ratio (1:1) controls the precursor hydrolysis rate. The effect of step six is ​​that increasing the argon ratio can suppress the hydrolysis of tetraethyl orthosilicate, generating uniform SiO2 nanoparticles of 200±50nm, forming a micro-nano rough structure.

[0076] The fluorosilane modification technique in steps eight and nine involves depositing PFOTS (fluorosilane) at 130°C and 35 Pa for 60 minutes. The effect of this step is the formation of a covalently bonded Si-O-Si-F layer (FTIR 1105 cm⁻¹). Characteristic peaks), fluorocarbon chain coverage ≥98% (XPS verification), achieving superoleophobicity (water contact angle >150°, oil contact angle >140°).

[0077] Coating performance verification:

[0078]

[0079] According to the above coating performance verification, the coating particles generated in situ by the sol-gel method and modified with gaseous fluorosilane form a micro-nano rough structure and a low surface energy fluorocarbon chain. The coating has a water contact angle of >150° and an oil contact angle of >140°. After 500 wear tests, it still maintains a hydrophobicity of >130°, which significantly reduces the oil adhesion rate.

[0080] Example 2

[0081] like Figure 2 B and Figure 5 As shown, the preparation of a long-lasting oleophobic coating on the inner surface of a gas pipeline includes the following steps:

[0082] Preprocessing (Steps 1-4):

[0083] Step 1: After cleaning and drying the pipe to be prepared, place it into a custom-made cylindrical vacuum chamber;

[0084] Step 2: Pre-evacuate the cylindrical vacuum chamber to the required pressure. Pa, then a mixture of high-purity oxygen and argon is introduced into the cylindrical vacuum chamber;

[0085] In this step, the volume ratio of oxygen to argon is 3:1, and the total flow rate of the mixture of high-purity oxygen and argon injected into the cylindrical vacuum chamber is 70 sccm; pollutants are adsorbed by bombardment with argon ions in the argon gas, and active oxygen species are generated by oxygen ionization.

[0086] Step 3: Turn on the radio frequency plasma generator to activate the mixed gas in the cylindrical vacuum chamber and the inner or outer surface of the pipes with plasma.

[0087] Mixed gas It ionizes to generate reactive oxygen free radicals, which oxidize surface contaminants.

[0088] In this step, the frequency of the radio frequency plasma generator is 13.56MHz, the operating power is 400W (optimal), and the duration is 15 minutes.

[0089] Step 4: Turn off the radio frequency plasma generator and passivate the tube by introducing argon gas for 5 minutes. Then, place the passivated and cooled tube into a double-walled quartz tube furnace.

[0090] Argon ion bombardment strips away the micro-adsorption layer, implanting hydroxyl groups at a density of up to [missing information]. groups / cm² (XPS verification).

[0091] The preprocessing can be summarized as follows:

[0092] Pipeline cleaning: Use ethanol for ultrasonic cleaning for 15 minutes to remove grease and particulate matter.

[0093] Plasma activation: RF power 400W (optimal value), time 15min;

[0094] Mixed gas It ionizes to generate reactive oxygen free radicals, which oxidize surface contaminants;

[0095] Argon ion bombardment strips away the micro-adsorption layer, implanting hydroxyl groups at a density of up to [missing information]. groups / cm² (XPS verification);

[0096] Coating particle deposition (steps five and six):

[0097] Step 5: Use a precursor evaporation system to vaporize the premixed liquid of tetraethyl orthosilicate and ethanol to form a precursor, and inject the precursor into a double-walled quartz tube furnace by a mixed gas of nitrogen and argon.

[0098] In this step, the precursor evaporation system includes a temperature-controlled flash tank set at 85°C to vaporize tetraethyl orthosilicate and ethanol in a volume ratio of 1:10.

[0099] Step Six: Adjust the surface temperature of the pipeline by controlling the ratio of nitrogen to argon. Coating particle growth size;

[0100] The summary of coating particle deposition is as follows:

[0101] Ethyl orthosilicate / ethanol premix (1:10) was vaporized in an 85°C flash evaporator, and then... Carried by a mixture of gases (1:1 ratio);

[0102] The double-walled quartz furnace was set at 180℃ and 80Pa for 40 minutes.

[0103] Particle size control: Increasing the argon ratio and decreasing the particle size (argon gas inhibits the hydrolysis rate of tetraethyl orthosilicate) yielded a uniform particle size of 200±50 nm. Nanoparticles (SEM verification).

[0104] Microwave interference (step seven):

[0105] Step 7: Use a microwave interferometry system to perform microwave interferometry on the inner surface of the pipe to increase the density of the inner surface at the center of the pipe. Coating particle growth rate;

[0106] The microwave interferometer system includes a microwave transmitter A and an intermediate diffraction layer;

[0107] The microwave transmitter A is used to transmit sinusoidal microwaves with a frequency of 2.45 GHz and a power of 500 W into the intermediate diffraction layer;

[0108] The intermediate diffraction layer includes diffraction gratings A1 and A2.

[0109] Among them, the microwave generated by microwave transmitter A enters diffraction grating A1 and diffraction grating A2 and generates new sinusoidal microwaves respectively. The superposition region of the two new sinusoidal microwaves is located in the middle region of the pipe.

[0110] Fluorosilane modification (steps eight to nine):

[0111] Step 7: Deposit The coated particles are transferred to the CVD reaction chamber and evacuated to pressure. Pa, then flush with dry nitrogen for 10 minutes to remove residual volatile substances;

[0112] Step 8: Place the fluorosilane in a constant temperature vaporization chamber (100°C) and introduce high-purity nitrogen or argon as a carrier gas. The carrier gas flow rate is 10–20 sccm to carry the fluorosilane vapor into the CVD reaction chamber.

[0113] Step 9: The fluorosilane is perfluorooctyltrichlorosilane. The deposition temperature of the fluorosilane vapor in the CVD reaction chamber is 120-150℃, the pressure is 20-50Pa, and the deposition time is 50-70 minutes, forming a covalently bonded Si-O-Si-F low surface energy layer.

[0114] The summary of fluorosilane modification is as follows:

[0115] Perfluorooctyltrichlorosilane is vaporized in a vaporization chamber at 100°C and carried to the CVD reaction chamber by a nitrogen carrier gas (15 sccm).

[0116] Deposition parameters: 130℃, 35Pa, 60min, forming Si-O-Si-F covalent bonds (FTIR detection at 1105 cm⁻¹). Characteristic peaks);

[0117] Surface fluorocarbon chain coverage ≥98% (XPS-F1s peak intensity ratio).

[0118] Among them, the working principle of microwave interferometry system ( Figure 3 (as shown)

[0119] The diffraction gratings A1 / A2 split the incident microwave (2.45 GHz) into two coherent waves;

[0120] Precisely locate the interference superposition zone to the center of the pipeline ( Figure 3 Red zone), forming local energy focus (intensity increased by 3 times);

[0121] Mechanism of action: Microwave thermal effect accelerates TEOS hydrolysis and promotes... Nucleation and growth occur in the central region.

[0122] Process parameter optimization (step seven):

[0123] Microwave power 500W (optimal value), frequency 2.45GHz;

[0124] Interference time of 20 minutes increased the particle growth rate in the central region by 40% (compared to the port region).

[0125] Results: The uniformity of the inner wall coating thickness is ≤ ±5% (measured by SEM cross-section).

[0126] Summary of the technical content and effects of the above steps:

[0127] The specific technical content of microwave interference in step seven is as follows: 2.45 GHz microwaves are split by a diffraction grating to form an interference region at the center of the pipe (power 500W, 20 minutes). The effect of step seven is to increase the energy intensity of the interference region by 3 times, accelerate the hydrolysis and nucleation of TEOS in the central region, increase the growth rate of the central coating by 40%, and increase the thickness from 0.3 μm to 1.10 μm.

[0128] The specific technical content of the fluorosilane modification in steps eight and nine is as follows (same as in Example 1): PFOTS (fluorosilane) is deposited at 130°C and 35 Pa for 60 minutes. The effect of this step is that the oleophobic properties of the central area are significantly improved, the water contact angle is 150°±1.8°, the oil contact angle is 141°±2.2°, and the oil adhesion rate is greatly reduced.

[0129] Compared to microwave interference, the non-microwave interference method solves the problem that the inner wall coating is thicker closer to the pipe opening and thinner closer to the pipe center. This significantly increases the growth rate of the inner wall coating, thereby ensuring uniform inner wall thickness and completely resolving the difference in coating thickness between the port and the center caused by insufficient particle diffusion in traditional processes.

[0130] Comparison data:

[0131] Region Thickness of coating without microwave interference Thickness of coating after microwave interference At the port of the pipe 1.2 pm 1.15 pm At the center of the pipe 0.3 pm 1.10 pm

[0132] Coating performance verification:

[0133]

[0134] The above coating performance verification shows that the microwave interference system can accurately focus energy to the central area of ​​the pipeline, which greatly improves the growth rate of the coating in the center of the inner wall. This ensures uniform inner wall thickness and completely solves the difference in coating thickness between the port and the center caused by insufficient particle diffusion in traditional processes, thus achieving uniform oil-repellent protection of the entire inner wall of the gas pipeline.

[0135] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A process for preparing long-lasting oleophobic coatings for pipelines based on chemical vapor deposition, characterized in that, Includes the following steps: S1. After cleaning and drying the pipe to be prepared, place it into a custom-made cylindrical vacuum chamber. S2. Pre-evacuate the cylindrical vacuum chamber to the required pressure. Pa, then a mixture of high-purity oxygen and argon is introduced into the cylindrical vacuum chamber; S3. Turn on the radio frequency plasma generator to activate the mixed gas in the cylindrical vacuum chamber and the inner or outer surface of the pipe with plasma. S4. Turn off the radio frequency plasma generator and introduce argon gas for 5 minutes for passivation cooling. Then put the passivated and cooled pipe into a double-walled quartz tube furnace. S5. A precursor is formed by vaporizing a premixed liquid of tetraethyl orthosilicate and ethanol using a precursor evaporation system, and the precursor is injected into a double-walled quartz tube furnace by a mixed gas of nitrogen and argon. S6. The growth size of coating particles on the pipe surface is controlled by adjusting the ratio of nitrogen to argon. S7. A microwave interference system is used to perform microwave interference on the inner surface of the pipe to increase the growth rate of coating particles at the inner surface of the pipe center. S8. Transfer the pipe after depositing the coated particles to the CVD reaction chamber and evacuate it to the required pressure. Pa, then flush with dry nitrogen for 10 minutes to remove residual volatile substances; S9. Place the fluorosilane in a constant temperature vaporization chamber and introduce high-purity nitrogen or argon as a carrier gas. The carrier gas flow rate is 10–20 sccm, so as to carry the fluorosilane vapor into the CVD reaction chamber.

2. The process for preparing a long-lasting oleophobic coating for pipelines based on chemical vapor deposition according to claim 1, characterized in that: In step S2, the volume ratio of oxygen to argon is 3:1, and the total flow rate of the mixture of high-purity oxygen and argon injected into the cylindrical vacuum chamber is 70 sccm; pollutants are adsorbed by bombardment with argon ions in the argon gas, and active oxygen species are generated by oxygen ionization.

3. The process for preparing a long-lasting oleophobic coating for pipelines based on chemical vapor deposition according to claim 1, characterized in that: In step S3, the frequency of the radio frequency plasma generator is 13.56MHz, the operating power range is 300W–500W, and the duration is 10–20 minutes.

4. The process for preparing a long-lasting oleophobic coating for pipelines based on chemical vapor deposition according to claim 1, characterized in that: In step S5, the precursor evaporation system includes a temperature-controlled flash tank set at 80-90°C to vaporize tetraethyl orthosilicate and ethanol in a volume ratio of 1:

10.

5. The process for preparing a long-lasting oleophobic coating for pipelines based on chemical vapor deposition according to claim 1, characterized in that: The microwave interferometer system includes a microwave transmitter A and an intermediate diffraction layer; The microwave transmitter A is used to transmit sinusoidal microwaves with a frequency of 2.45 GHz and a power of 400 W–600 W into the intermediate diffraction layer; The intermediate diffraction layer includes diffraction gratings A1 and A2.

6. The process for preparing a long-lasting oleophobic coating for pipelines based on chemical vapor deposition according to claim 5, characterized in that: The microwaves generated by the microwave transmitter A enter the diffraction gratings A1 and A2 and generate new sinusoidal microwaves respectively. The superposition region of the two new sinusoidal microwaves is located in the middle region of the pipe.

7. The process for preparing a long-lasting oleophobic coating for pipelines based on chemical vapor deposition according to claim 1, characterized in that: When preparing a coating on the outer surface of the pipe, after controlling particle growth in step S6, the pipe directly enters the CVD reaction chamber in step S8. When preparing a coating on the inner surface of the pipe, step S7 is required to use a microwave interference system to perform microwave interference on the inner surface of the pipe.

8. The process for preparing a long-lasting oleophobic coating for pipelines based on chemical vapor deposition according to claim 1, characterized in that: The fluorosilane is perfluorooctyltrichlorosilane. The fluorosilane vapor is deposited in the CVD reaction chamber at a temperature of 120-150℃, a pressure of 20-50Pa, and a deposition time of 50-70 minutes to form a covalently bonded Si-O-Si-F low surface energy layer.

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