A composite steel pipe lining and its molding and curing method

Abstract

This invention discloses a composite steel pipe lining and its molding and curing method, belonging to the technical field of pipeline anti-corrosion materials. The lining comprises a corrosion-resistant functional layer, an interface bonding layer, and a buffer transition layer arranged sequentially from the inside out. A three-step modification process is employed: a dopamine-based biomimetic adhesion layer, a fluorotantalic acid-boric acid low-temperature liquid-phase deposition tantalum pentoxide layer, and grafting open-ring fluorinated polyhedral oligomeric silsesquioxanes to treat basalt fibers, imparting superhydrophobic properties and a dense chemical protective barrier to the fibers. This lining transforms traditional passive corrosion protection into an active repulsion mode, effectively cutting off the penetration path of corrosive media and improving the chemical corrosion resistance, interface bonding strength, and thermal cycling stability of the composite steel pipe.

Description

Technical Field

[0001] This invention relates to the field of pipeline anti-corrosion materials and manufacturing technology, and more specifically, to a composite steel pipe lining and its forming and curing method. Background Technology

[0002] With the rapid development of petroleum, chemical, and municipal water supply industries, composite steel pipes are widely used in pipelines transporting various fluid media due to their excellent comprehensive mechanical properties and pressure-bearing capacity. To resist the erosion of corrosive media inside the pipeline, an anti-corrosion lining system is usually installed inside the steel pipe. Existing composite steel pipe linings generally include a corrosion-resistant functional layer, an interface bonding layer, and a buffer transition layer, arranged sequentially from the inside out. The corrosion-resistant functional layer is often composed of traditional inorganic fiber-reinforced resin-based composite materials. The buffer transition layer is usually an elastic polymer layer used to absorb the thermal expansion difference between the steel pipe matrix and the lining layer. The interface bonding layer utilizes a combination of thermosetting resin and inorganic fillers to provide good adhesion.

[0003] However, existing fiber-reinforced resin anti-corrosion liners are prone to significant structural defects and corrosion failure risks in harsh service environments. Firstly, the traditional inorganic reinforcing fibers (such as basalt fibers) commonly used in the lining functional layers have relatively smooth surfaces and are highly chemically inert, lacking active functional groups capable of chemically bonding with the resin matrix. This results in poor interfacial bonding between the fibers and the resin matrix. Under the combined effects of fluid scouring, pressure alternation, and temperature fluctuations encountered in daily pipeline operation, this weak physical interface is highly susceptible to microscopic debonding and stress microcracks.

[0004] Secondly, these microscopic interface defects often become natural channels for corrosive media to penetrate. Due to the insufficient density of the bond between the fiber and resin, corrosive media such as water, strong acids, and strong alkalis can easily penetrate through capillary action along the microscopic gaps between them, a phenomenon commonly known in the industry as water treeing. This deep penetration not only damages the network structure of the resin matrix, but more seriously, the ordinary inorganic fiber body and its bonding interface lack an effective protective barrier under extreme chemical environments, making them highly susceptible to direct dissolution and erosion by corrosive media. As the penetration depth of the corrosive media along the interface increases and the erosion reaction intensifies, it inevitably leads to large-area interface peeling inside the lining layer, a sharp decline in overall mechanical properties, and ultimately, the complete failure of the anti-corrosion system of the composite steel pipe.

[0005] In summary, how to break through the limitations of traditional anti-corrosion systems that passively rely on the resin matrix to block the medium, thoroughly improve the interfacial bonding state between inorganic reinforcing fibers and the resin matrix at the microscopic level, endow the fiber surface with a dense chemical protective barrier to resist bulk erosion, and establish a superhydrophobic interface with the ability to actively repel the medium to cut off the capillary penetration path, thereby significantly improving the long-term anti-corrosion life and overall structural stability of the composite steel pipe lining, is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] To address the technical problem of poor interfacial bonding between reinforcing fibers and resin matrix in existing composite steel pipe linings, which easily leads to capillary penetration of corrosive media and complete failure of the anti-corrosion system, the present invention aims to provide a composite steel pipe lining and its molding and curing method. The purpose is to impart dense physical protection and superhydrophobic liquid-repellent properties to the fibers through microscopic interface modification, completely cut off the media penetration path, and significantly improve the long-term anti-corrosion life and structural stability of the lining.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A composite steel pipe lining, comprising a corrosion-resistant functional layer, an interface bonding layer, and a buffer transition layer arranged sequentially from the inside to the outside.

[0009] The raw materials used to prepare the corrosion-resistant functional layer include 30 to 60 parts by weight of modified fiber, 40 to 70 parts by weight of resin matrix, and 1 to 10 parts by weight of curing agent; the raw materials used to prepare the interface bonding layer include 100 parts by weight of thermosetting resin and 10 to 30 parts by weight of inorganic filler; the raw materials used to prepare the buffer transition layer include 100 parts by weight of elastic polymer.

[0010] The raw materials used to prepare the modified fiber include 100 parts by weight of basalt fiber, 2 to 5 parts by weight of dopamine hydrochloride, 100 to 200 parts by weight of buffer solution, 5 to 15 parts by weight of fluorotantalic acid, 2 to 8 parts by weight of boric acid, 1 to 5 parts by weight of ring-opening fluorinated polyhedral oligomeric silsesquioxane, 0.1 to 1 part by weight of catalyst, and 50 to 150 parts by weight of organic solvent.

[0011] Furthermore, the buffer solution is specifically selected from one or more of the following: tris(hydroxymethyl)aminomethane hydrochloride buffer solution, phosphate buffer solution, and carbonate buffer solution.

[0012] Furthermore, the fluorotantalic acid is specifically selected from one or more of heptafluorotantalic acid aqueous solution, hexafluorotantalic acid aqueous solution, and potassium octafluorotantalate aqueous solution; the boric acid is specifically selected from one or more of orthoboric acid, metaboric acid, and tetraboric acid.

[0013] Furthermore, the open-ring fluorinated polyhedral oligomeric silsesquioxane is specifically selected from one or more of trifluoropropyl-substituted open-ring trisilol POSS and octa(trifluoropropyl)disilol polyhedral oligomeric silsesquioxane.

[0014] Furthermore, the catalyst is specifically selected from one or more of chloroplatinic acid, triethylamine, and dibutyltin dilaurate; the organic solvent is specifically selected from one or more of anhydrous ethanol, toluene, and tetrahydrofuran.

[0015] Furthermore, the resin matrix is ​​specifically selected from one or more of bisphenol A type epoxy resin, phthalic unsaturated polyester resin, and bisphenol A type vinyl ester resin; the curing agent is specifically selected from one or more of diethylenetriamine, methyltetrahydrophthalic anhydride, and methyl ethyl ketone peroxide.

[0016] Furthermore, the thermosetting resin is specifically selected from one or more of phenolic resin, urea-formaldehyde resin, and melamine-formaldehyde resin; the inorganic filler is specifically selected from one or more of silica powder, calcium carbonate powder, and barium sulfate powder; and the elastic polymer is specifically selected from one or more of polyurethane elastomer, ethylene propylene diene monomer (EPDM) rubber, and nitrile rubber.

[0017] Furthermore, EPDM rubber can be added to the corrosion-resistant functional layer in the inner lining of the composite steel pipe.

[0018] The present invention also provides a method for preparing the above-mentioned composite steel pipe lining, which includes the following steps:

[0019] The first step is to prepare the modified fiber: First, a biomimetic adhesion layer is constructed by immersing basalt fibers in a prepared buffer solution containing dopamine hydrochloride and continuously purging oxygen at room temperature for 12 to 24 hours. After the reaction, the fibers are thoroughly washed with deionized water and vacuum dried at 60 to 80 degrees Celsius to obtain pretreated fibers with a polydopamine coating. Next, low-temperature liquid phase deposition is performed by immersing the pretreated fibers in a mixed aqueous solution containing fluorotantalic acid and boric acid and reacting at a constant temperature of 35 to 50 degrees Celsius for 12 to 48 hours. The boric acid consumes free fluoride ions in the solution, breaking the chemical equilibrium and in-situ inducing hydrolysis to deposit a dense tantalum pentoxide transition layer on the surface of the polydopamine layer. After the reaction, the fibers are removed, washed with deionized water, and dried at 70 to 90 degrees Celsius to obtain fibers with a tantalum pentoxide layer. Finally, superhydrophobic interface grafting is performed. The fiber with the tantalum pentoxide layer is immersed in an organic solvent containing an open-ring fluorinated polyhedral oligomeric silsesquioxane and a catalyst, and refluxed at 60 to 90 degrees Celsius for 6 to 12 hours. After the reaction, the fiber is washed with organic solvent and deionized water in sequence, and then dried at 80 to 100 degrees Celsius to obtain the desired modified fiber.

[0020] The second step is to prepare the slurry for each layer: the modified fiber is mixed evenly with the resin matrix and curing agent to obtain the corrosion-resistant functional layer slurry; the thermosetting resin is mixed evenly with the inorganic filler to obtain the interface bonding layer slurry; and the elastic polymer is prepared as the raw material for the buffer transition layer.

[0021] The third step is the forming and curing of the inner lining: The buffer transition layer material, the interface bonding layer slurry, and the corrosion-resistant functional layer slurry are sequentially coated or formed on the inner wall of the composite steel pipe. After coating or forming, a curing treatment is carried out under stepped heating conditions, gradually increasing the temperature from room temperature to 150 degrees Celsius for 2 to 10 hours, allowing the elastomer, interface bonding resin, and corrosion-resistant layer resin to achieve co-curing and cross-linking. Finally, a composite steel pipe inner lining layer is formed inside the steel pipe substrate, consisting of a corrosion-resistant functional layer, an interface bonding layer, and a buffer transition layer arranged sequentially from the inside out.

[0022] In the composite steel pipe lining and its forming and curing method of the present invention, there is a significant deep synergistic mechanism among the various raw material components and preparation steps: First, dopamine hydrochloride undergoes an oxidation reaction in a buffer solution, constructing a polydopamine biomimetic adhesion layer on the surface of basalt fibers. This polydopamine layer has extremely strong adhesion properties, not only constructing a rough micro-substrate on the originally smooth inorganic fiber surface, significantly increasing the mechanical interlocking effect, but also providing a large number of abundant active functional groups such as hydroxyl and amino groups on the fiber surface. These functional groups act as strong chemical anchors, providing a basis for subsequent inorganic deposition. The organic grafting reaction provides strong bonding sites, improving the problems of high surface inertness and poor interfacial bonding with the resin matrix in traditional inorganic fibers. Secondly, during the low-temperature liquid phase deposition process, fluorotantalic acid and boric acid work synergistically. Boric acid continuously consumes free fluoride ions in the mixed solution, thus breaking the hydrolysis equilibrium and inducing the in-situ deposition of a dense tantalum pentoxide transition layer on the polydopamine layer surface. This tantalum pentoxide layer has extremely high chemical stability and density, effectively coating the fiber with a high-density ceramic anti-corrosion coating, effectively blocking corrosive media such as water molecules, strong acids, and strong alkalis from affecting the fiber. The process involved direct dissolution and chemical erosion of the Wuyan fiber matrix and the polydopamine interface. Subsequently, under the action of a catalyst, an open-ring fluorinated polyhedral oligomeric silsesquioxane underwent a grafting reaction with defect sites in the tantalum pentoxide layer and residual active groups in the polydopamine layer. This introduced a low surface energy fluorinated polyhedral oligomeric silsesquioxane structure into the outermost layer of the fiber, successfully constructing a superhydrophobic interface. The effect of this superhydrophobic interface generated strong capillary repulsion, actively and completely rejecting moisture and corrosive media, and completely cutting off the water treeing phenomenon of corrosive media along the micro-interface between the resin matrix and the fiber. The invention utilizes the physical pathways of phagocytosis and capillary penetration. Ultimately, through the deep synergy of three microscopic mechanisms—the enhanced adhesion of polydopamine, the dense physical barrier of tantalum pentoxide, and the superhydrophobic active liquid repellency of open-ring fluorinated polyhedral oligomeric silsesquioxane—this invention transforms the traditional anti-corrosion lining system, which passively relies on the resin matrix to block the medium, into a system that actively relies on the fiber micro-interface to repel the medium. This effectively prevents large-area interfacial peeling and overall mechanical property degradation within the lining layer, thereby improving the long-term anti-corrosion life, pressure-bearing capacity, and overall structural stability of the composite steel pipe lining.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] 1. Polydopamine not only constructs a rough microstructure on the fiber surface to enhance the mechanical interlocking effect, but also provides abundant active functional groups as strong chemical anchors. This structure enhances the interfacial bonding strength, effectively preventing micro-debonding and stress microcracks in composite steel pipes under complex working conditions such as fluid scouring, pressure alternation, and temperature fluctuations, thus significantly improving the overall structural stability of the inner lining.

[0025] 2. The tantalum pentoxide transition layer possesses excellent chemical stability and physical density, forming a high-strength anti-corrosion armor on the fiber exterior. This protective layer can prevent water molecules and corrosive media such as strong acids and alkalis from directly contacting and dissolving the fiber body and interfacial bonding, thereby ensuring the structural integrity of the fiber-reinforced skeleton under harsh chemical environments.

[0026] 3. The introduction of open-ring fluorinated polyhedral oligomeric silsesquioxane endows the fiber surface with extremely low surface energy and superhydrophobic properties. The resulting strong capillary repulsion completely cuts off the physical path of the medium penetrating deep into the inner lining along the microscopic gaps. Through the synergistic effect of polydopamine's enhanced adhesion, tantalum pentoxide's dense barrier, and fluorosiloxane's superhydrophobic liquid repellency, this invention successfully transforms the passive blocking mode of the traditional anti-corrosion system into an active repulsion mode, effectively preventing interfacial peeling and mechanical property degradation of the inner lining. Attached Figure Description

[0027] Figure 1 This is a structural schematic diagram of a composite steel pipe according to the present invention.

[0028] Figure 2 This is a comparison diagram of the static water contact angle between the embodiments and comparative examples of the present invention.

[0029] Figure 3 This is a comparison diagram of the corrosion resistance performance of the embodiments and comparative examples of the present invention. Detailed Implementation

[0030] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] This embodiment provides a composite steel pipe lining and its specific molding and curing method. The composite steel pipe lining includes a corrosion-resistant functional layer, an interface bonding layer and a buffer transition layer arranged sequentially from the inside to the outside.

[0033] 1. Raw material formula (parts by weight):

[0034] The raw materials used to prepare the modified fiber include: 100 parts by weight of basalt fiber, 3 parts by weight of dopamine hydrochloride, 150 parts by weight of tris(hydroxymethyl)aminomethane hydrochloride buffer solution, 10 parts by weight of heptafluorotantalic acid aqueous solution, 5 parts by weight of orthoboric acid, 3 parts by weight of trifluoropropyl-substituted open-ring trisilyl alcohol POSS, 0.5 parts by weight of chloroplatinic acid, and 100 parts by weight of anhydrous tetrahydrofuran.

[0035] CAS number of trifluoropropyl-substituted open-ring trisilyl alcohol POSS: 656800-09-8;

[0036] The specifications for the tris(hydroxymethyl)aminomethane hydrochloride buffer solution are: 0.1M, pH 8.5 (prepared by mixing tris(hydroxymethyl)aminomethane and hydrochloric acid in a standard ratio, with deionized water as the solvent);

[0037] The specifications for heptafluorotantalic acid aqueous solution are: concentration of 40wt% (H2TaF7 content 40%, solvent is deionized water).

[0038] The raw materials used to prepare the corrosion-resistant functional layer include: 45 parts by weight of the above-mentioned modified fiber, 55 parts by weight of bisphenol A type epoxy resin, and 5 parts by weight of diethylenetriamine.

[0039] The bisphenol A type epoxy resin was purchased from Sinopec Hunan Petrochemical Co., Ltd., and the model number is YDB-500.

[0040] The raw materials used to prepare the interface bonding layer include: 100 parts by weight of phenolic resin and 20 parts by weight of silica powder.

[0041] The phenolic resin was purchased from Sumitomo Bakelite Co., Ltd., model number PR-217.

[0042] The raw materials used to prepare the buffer transition layer include: 100 parts by weight of polyurethane elastomer;

[0043] The polyurethane elastomer was purchased from Bohua Tian Rubber & Plastics Technology Co., Ltd., model number HT1195A-4.

[0044] 2. Preparation method:

[0045] The first step is to prepare modified fibers:

[0046] (1) Construction of biomimetic adhesive layer: 100 parts by weight of basalt fiber were cut into short fibers with a length of 80±10 mm and immersed in 150 parts by weight of tris(hydroxymethyl)aminomethane hydrochloride buffer solution (pH=8.5) containing 3 parts by weight of dopamine hydrochloride. Clean oxygen was continuously introduced at a flow rate of 0.5 L / min at room temperature (25±2℃) and the reaction was slowly stirred at 100 rpm for 18 hours. After the reaction, the fibers were repeatedly washed with deionized water until the washing liquid was colorless and the pH value was neutral (pH=6.5-7.5). The fibers were vacuum dried for 4 hours at 70±2℃ and vacuum degree ≤-0.08 MPa to obtain pretreated fibers with polydopamine coating on the surface.

[0047] (2) Low-temperature liquid phase deposition: Prepare 200 parts by weight of a mixed aqueous solution containing 10 parts by weight of heptafluorotantalic acid and 5 parts by weight of orthoboric acid, and adjust the pH value to 2.0-3.0 with hydrochloric acid or sodium hydroxide solution; completely immerse the pretreated fiber in the mixed solution and react for 24 hours under constant temperature conditions of 40±1℃ in a water bath, stirring slowly at 60 rpm during the reaction; after the reaction, take out the fiber, wash it repeatedly with deionized water until the pH value of the washing solution is 6.5-7.5 (neutral), and dry it in a forced-air drying oven at 80±2℃ for 6 hours to obtain a fiber with a tantalum pentoxide layer;

[0048] (3) Superhydrophobic interface grafting: 3 parts by weight of trifluoropropyl-substituted open-ring trisilyl alcohol POSS was dissolved in 100 parts by weight of anhydrous ethanol, and 0.5 parts by weight of chloroplatinic acid was added as a catalyst. The mixture was ultrasonically dispersed (power 200W, frequency 40kHz) for 15 minutes until completely dissolved to obtain a grafting reaction solution. The fiber with the above-mentioned tantalum pentoxide layer was immersed in the reaction solution and refluxed in an oil bath at 75±2℃ for 8 hours. After the reaction, the fiber was washed 3 times each with anhydrous ethanol and deionized water. After each washing, the fiber was separated by centrifugation (speed 3000rpm, time 5 minutes). Then, the fiber was dried in a vacuum drying oven at 90±2℃ for 8 hours to obtain the modified fiber.

[0049] The second step is to prepare the slurry for each layer:

[0050] Add 45 parts by weight of the above modified fiber, 55 parts by weight of bisphenol A epoxy resin, and 5 parts by weight of diethylenetriamine to a high-speed mixer in sequence. Set the speed to 800 r / min and stir and mix for 30 minutes at an ambient temperature of 25±2℃ until the modified fiber is evenly dispersed and there is no agglomeration. Let it stand for 10 minutes to defoam before use.

[0051] 100 parts by weight of phenolic resin were preheated to 60±2℃ to reduce viscosity, and added to a ball mill with 20 parts by weight of silica powder. The ball-to-material mass ratio was 3:1. The speed was set to 300 rpm, and the mixture was ball-milled and dispersed for 2 hours until the filler was evenly dispersed and there was no particle feel, thus obtaining the interface bonding layer slurry.

[0052] After slicing 100 parts by weight of polyurethane elastomer, preheat it in an oven at 60±2℃ for 2 hours to soften it to a sprayable state for later use.

[0053] The third step is the molding and curing of the inner lining layer.

[0054] The composite steel pipe substrate, after surface degreasing and sandblasting (Sa2.5 grade), is preheated to 40±5℃. A high-pressure airless spraying device (spray gun pressure 15MPa, nozzle diameter 0.5mm) is used to uniformly spray the preheated polyurethane elastomer onto the inner wall of the steel pipe. The spraying speed is controlled at 40cm / s, the ambient temperature is maintained at 25℃, the relative humidity is ≤70%, and the spraying thickness is controlled at 1.5mm. After spraying, the substrate is left to stand for 20 minutes until it is surface dry (touch dry, no stickiness) but not completely cured internally, reaching a semi-cured state.

[0055] While the buffer transition layer is in a semi-cured state (the surface is slightly sticky but does not stick to gloves), immediately apply the above interface bonding layer slurry evenly to the surface of the buffer transition layer using a scraper. The scraper gap is set to 1.0 mm, the coating speed is 15 cm / s, and the thickness is controlled to be 1.0 mm. After coating, let it stand for 10 minutes to level.

[0056] After the interface bonding layer has dried (the solvent has evaporated until the surface is no longer glossy), the corrosion-resistant functional layer slurry is evenly sprayed onto the surface of the interface bonding layer using air pressure spraying (spray gun pressure 0.5MPa, nozzle diameter 1.5mm). The spraying speed is 30cm / s, the spraying thickness is 3.0mm, and the ambient temperature is maintained at 25℃ and the relative humidity is ≤60% during spraying.

[0057] After coating, the composite steel pipe is placed in a rotary curing oven and heated from room temperature to 80±2℃ at a heating rate of 5℃ / min, and held for 1 hour; then heated to 120±2℃ at a heating rate of 3℃ / min, and held for 1 hour; finally heated to 150±2℃ at a heating rate of 2℃ / min, and held for 4 hours, for a total curing time of 8 hours. During the curing process, the steel pipe is kept rotating slowly at 5 rpm to ensure uniform coating. After curing, the pipe is cooled to room temperature in the oven, and finally a composite steel pipe lining layer is formed inside the steel pipe substrate, consisting of a corrosion-resistant functional layer, an interface bonding layer, and a buffer transition layer arranged sequentially from the inside to the outside.

[0058] Example 2

[0059] This embodiment provides a composite steel pipe lining and its specific molding and curing method, with the raw material composition and preparation method referring to Embodiment 1.

[0060] Compared to Example 1, the trifluoropropyl-substituted open-ring trisiloxane POSS in Example 1 is replaced with octa(trifluoropropyl)disiloxane polyhedral oligomeric silsesquioxane, and the rest remains the same as in Example 1.

[0061] The CAS number for octa(trifluoropropyl)disilol polyhedral oligomeric silsesquioxane is 854151-28-3.

[0062] Example 3

[0063] This embodiment provides a composite steel pipe lining and its specific molding and curing method, with the raw material composition and preparation method referring to Embodiment 1.

[0064] Compared to Example 1, the orthoboric acid in Example 1 is replaced with metaboric acid, while the rest remains the same as in Example 1.

[0065] Example 4

[0066] This embodiment provides a composite steel pipe lining and its specific molding and curing method, with the raw material composition and preparation method referring to Embodiment 1.

[0067] Compared to Example 1, the heptafluorotantalic acid aqueous solution in Example 1 was replaced with a hexafluorotantalic acid aqueous solution (40 wt%), and the rest remained the same as in Example 1.

[0068] Example 5

[0069] This embodiment provides a composite steel pipe lining and its specific molding and curing method, with the raw material composition and preparation method referring to Embodiment 1.

[0070] Compared to Example 1, the tetrahydrofuran in Example 1 is replaced with toluene, while the rest remains the same as in Example 1.

[0071] Comparative Example 1

[0072] This comparative example provides a composite steel pipe lining and its specific molding and curing method, with the raw material composition and preparation method referring to Example 1.

[0073] Compared to Example 1, the modified fiber in Example 1 was replaced with basalt fiber modified with KH550 coupling agent, while the rest remained the same as in Example 1.

[0074] The preparation method of KH550 coupling agent modified basalt fiber is referenced in: Liao Junjie, Guo Runjie, Zhang Jingjiaming, et al. Effects of acid-base etching and silane coupling agent modification on the mechanical properties of basalt fiber composites [J]. Plastics Technology, 2025, 53(06):100-104.

[0075] Comparative Example 2

[0076] This comparative example provides a composite steel pipe lining and its specific molding and curing method, with the raw material composition and preparation method referring to Example 1.

[0077] Compared to Example 1, the "superhydrophobic interface grafting" step is not performed in the preparation of modified fibers, and the rest remains the same as in Example 1.

[0078] Comparative Example 3

[0079] This comparative example provides a composite steel pipe lining and its specific molding and curing method, with the raw material composition and preparation method referring to Example 1.

[0080] Compared to Example 1, the "low-temperature liquid phase deposition" step is omitted in the preparation of the modified fiber, while the rest remains the same as in Example 1.

[0081] Comparative Example 4

[0082] This comparative example provides a composite steel pipe lining and its specific molding and curing method, with the raw material composition and preparation method referring to Example 1.

[0083] Compared to Example 1, the "biomimetic adhesive layer construction" step is omitted in the preparation of modified fibers, while the rest remains the same as in Example 1.

[0084] That is, LPD deposition is not performed directly on basalt fibers.

[0085] Comparative Example 5

[0086] This comparative example provides a composite steel pipe lining and its specific molding and curing method, with the raw material composition and preparation method referring to Example 1.

[0087] Compared to Example 1, the modified fiber was replaced with ordinary basalt fiber, while the rest remained the same as in Example 1.

[0088] Comparative Example 6

[0089] This comparative example provides a composite steel pipe lining and its specific molding and curing method, with the raw material composition and preparation method referring to Example 1.

[0090] Compared to Example 1, the dopamine hydrochloride was replaced with 3,4-dihydroxyphenylacetic acid, and the rest remained the same as in Example 1.

[0091] Comparative Example 7

[0092] This comparative example provides a composite steel pipe lining and its specific molding and curing method, with the raw material composition and preparation method referring to Example 1.

[0093] Compared to Example 1, the trifluoropropyl-substituted open-ring trisilyl alcohol POSS was replaced with KH550, and the rest remained the same as in Example 1.

[0094] Performance testing:

[0095] 1. Hydrophobicity test: The static water contact angle (WCA) of the corrosion-resistant functional layer surface was measured using a contact angle meter. The fiber bundle or coating surface was flattened and fixed, and 2 μL of deionized water was added. After the droplet stabilized, the contact angle value was read. The data are shown in Table 1.

[0096] 2. Chemical Corrosion Resistance Test: The composite steel pipe lining samples were immersed in standard corrosive media, including 1 mol / L sulfuric acid solution (simulating acidic corrosion) and 1 mol / L sodium hydroxide solution (simulating alkaline corrosion). The immersion condition was a constant temperature of 60℃. After 30 days, the samples were removed, rinsed with deionized water, dried, and the mass retention rate was tested. The mass of the samples before and after immersion was weighed, and the mass loss rate was calculated. The data are shown in Table 1.

[0097] 3. Thermal aging and temperature cycling performance test: Simulating the temperature fluctuation conditions of the composite steel pipe in actual service, the samples were subjected to a thermal cycling test between -40℃ and 120℃, with 50 cycles. Each cycle involved holding the samples at both the low and high temperature ends for 1 hour, with a transition time not exceeding 5 minutes. After the cycling was completed, the interlaminar shear strength retention rate of the samples was tested, and the data are shown in Table 1.

[0098] Shear strength reference: JC / T773-2010.

[0099] Table 1

[0100] Static water contact angle (°) Acid loss rate (%) Alkali loss rate (%) Shear strength retention rate (%) Example 1 158.5 0.8 0.6 96.5 Example 2 156.2 0.9 0.7 96.8 Example 3 157.8 0.85 0.65 95.2 Example 4 155.6 0.95 0.75 93.5 Example 5 157.3 0.87 0.68 94.8 Comparative Example 1 82.3 6.2 5.8 75.3 Comparative Example 2 95.6 5.8 5.2 78.5 Comparative Example 3 78.4 8.5 7.8 72.1 Comparative Example 4 75.2 9.2 8.5 68.7 Comparative Example 5 68.5 12.5 11.2 55.2 Comparative Example 6 88.7 7.1 6.5 83.8 Comparative Example 7 85.1 6.8 6.1 78.5

[0101] The embodiments prepared using the complete multi-step modification process of this invention are at the optimal level in terms of hydrophobicity, acid and alkali corrosion resistance, and interfacial bonding retention after thermal cycling. However, the comparative examples that lack any modification step or use traditional modifiers show significant attenuation of various anti-corrosion and mechanical properties to varying degrees. Unmodified or conventionally coupled inorganic fibers, due to their high surface chemical inertness and lack of effective protection, are highly susceptible to capillary penetration of corrosive media along interfacial gaps, which can damage the overall structure. If the polydopamine layer is missing in the process, the fiber surface loses the microscopic rough substrate that enhances mechanical interlocking and the active chemical anchors for subsequent reactions, resulting in a significant decrease in the interlaminar shear strength of the liner layer against thermal aging and stress alternation. If the tantalum pentoxide layer is missing, it is equivalent to removing the dense inorganic physical corrosion protection, leaving the fiber body and bonding interface unprotected, and its ability to resist direct dissolution by acid and alkali solutions and chemical erosion is significantly reduced. If the open-ring fluorinated polyhedral oligomeric silsesquioxane is not grafted, the liner layer cannot construct a superhydrophobic interface with extremely low surface energy, thus losing the capillary repulsion force that actively repels water molecules and failing to fundamentally cut off the deep penetration path of corrosive media. In summary, only by deeply synergizing the three effects of polydopamine's enhanced adhesion, tantalum pentoxide's dense barrier, and fluorosiloxane's superhydrophobic liquid repellency, and transforming the anti-corrosion system from passively relying on resin blocking to actively relying on interface repulsion, can the overall anti-corrosion life and structural stability of the composite steel pipe lining be fully guaranteed and significantly improved.

[0102] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A composite steel pipe lining, characterized in that, The composite steel pipe lining includes a corrosion-resistant functional layer, an interface bonding layer, and a buffer transition layer arranged sequentially from the inside to the outside. The raw materials used to prepare the corrosion-resistant functional layer include 30 to 60 parts by weight of modified fiber, 40 to 70 parts by weight of resin matrix, and 1 to 10 parts by weight of curing agent. The raw materials used to prepare the interface bonding layer include 100 parts by weight of thermosetting resin and 10 to 30 parts by weight of inorganic filler. The raw materials used to prepare the buffer transition layer include 100 parts by weight of an elastic polymer; The raw materials used to prepare the modified fiber include 100 parts by weight of basalt fiber, 2 to 5 parts by weight of dopamine hydrochloride, 100 to 200 parts by weight of buffer solution, 5 to 15 parts by weight of fluorotantalic acid, 2 to 8 parts by weight of boric acid, 1 to 5 parts by weight of ring-opening fluorinated polyhedral oligomeric silsesquioxane, 0.1 to 1 part by weight of catalyst, and 50 to 150 parts by weight of organic solvent.

2. The composite steel pipe lining according to claim 1, characterized in that, The buffer solution is selected from one or more of the following: trihydroxymethylaminomethane hydrochloride buffer solution, phosphate buffer solution, and carbonate buffer solution.

3. The composite steel pipe lining according to claim 1, characterized in that, The fluorotantalic acid is selected from one or more of heptafluorotantalic acid aqueous solution, hexafluorotantalic acid aqueous solution, and potassium octafluorotantalate aqueous solution; The boric acid is selected from one or more of orthoboric acid, metaboric acid, and tetraboric acid.

4. The composite steel pipe lining according to claim 1, characterized in that, The open-ring fluorinated polyhedral oligosilsesquioxane is selected from one or more of trifluoropropyl-substituted open-ring trisilol POSS and octa(trifluoropropyl)disilol polyhedral oligosilsesquioxane.

5. The composite steel pipe lining according to claim 1, characterized in that, The catalyst is selected from one or more of chloroplatinic acid, triethylamine, and dibutyltin dilaurate; The organic solvent is selected from one or more of anhydrous ethanol, toluene, and tetrahydrofuran.

6. The composite steel pipe lining according to claim 1, characterized in that, The resin matrix is ​​selected from one or more of bisphenol A type epoxy resin, phthalic unsaturated polyester resin, and bisphenol A type vinyl ester resin; The curing agent is selected from one or more of diethylenetriamine, methyltetrahydrophthalic anhydride, and methyl ethyl ketone peroxide.

7. The composite steel pipe lining according to claim 1, characterized in that, The thermosetting resin is selected from one or more of phenolic resin, urea-formaldehyde resin, and melamine-formaldehyde resin; The inorganic filler is selected from one or more of silica powder, calcium carbonate powder, and barium sulfate powder; The elastic polymer is selected from one or more of polyurethane elastomers, EPDM rubber, and nitrile rubber.

8. A method for preparing a composite steel pipe lining as described in any one of claims 1 to 7, characterized in that, Includes the following steps: The first step is to prepare modified fibers: basalt fibers are immersed in a buffer solution containing dopamine hydrochloride and oxygen is continuously introduced at room temperature to react. After the reaction is completed, the fibers are washed with deionized water and vacuum dried to obtain pretreated fibers with a polydopamine coating on the surface. The pretreated fiber was immersed in a mixed aqueous solution containing fluorotantalic acid and boric acid, and reacted at a constant temperature. After the reaction was completed, it was washed and dried with deionized water to obtain fiber with a tantalum pentoxide layer. The fiber with the tantalum pentoxide layer was immersed in an organic solvent containing an open-ring fluorinated polyhedral oligomeric silsesquioxane and a catalyst, and the reaction was refluxed. After the reaction was completed, the fiber was washed with organic solvent and deionized water in sequence and dried to obtain the modified fiber. The second step is to prepare the slurry for each layer: the modified fiber is mixed evenly with the resin matrix and curing agent to obtain the corrosion-resistant functional layer slurry; the thermosetting resin is mixed evenly with the inorganic filler to obtain the interface bonding layer slurry; and an elastic polymer is prepared as the raw material for the buffer transition layer. The third step is the forming and curing of the inner lining: the buffer transition layer material, the interface bonding layer slurry, and the corrosion-resistant functional layer slurry are sequentially coated or formed on the inner wall of the composite steel pipe. After coating or forming, the lining is cured under stepped heating conditions to form a composite steel pipe inner lining consisting of a corrosion-resistant functional layer, an interface bonding layer, and a buffer transition layer arranged sequentially from the inside to the outside of the steel pipe substrate.

9. The method for preparing the composite steel pipe lining according to claim 8, characterized in that, In the first step, the basalt fiber is immersed in a buffer solution containing dopamine hydrochloride and oxygen is continuously introduced at room temperature for 12 to 24 hours, and the vacuum drying temperature is 60 to 80 degrees Celsius. The pretreated fibers are immersed in a mixed aqueous solution containing fluorotantalic acid and boric acid at a constant temperature of 35 to 50 degrees Celsius for 12 to 48 hours, and then dried at a temperature of 70 to 90 degrees Celsius after washing. The fiber with the tantalum pentoxide layer is immersed in an organic solvent containing an open-ring fluorinated polyhedral oligomeric silsesquioxane and a catalyst. The reflux reaction temperature is 60 to 90 degrees Celsius, the reflux reaction time is 6 to 12 hours, and the drying temperature after washing is 80 to 100 degrees Celsius.

10. The method for preparing the composite steel pipe lining according to claim 8, characterized in that, In the third step, the curing process under stepped heating conditions involves raising the temperature from room temperature to 150 degrees Celsius, and the curing time is 2 to 10 hours.

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