A heteropoly acid intercalated graphene-epoxy anticorrosive coating and a preparation method thereof

Abstract

This invention belongs to the field of pipeline anti-corrosion coating technology, specifically relating to a heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating and its preparation method. The heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating, by weight percentage, comprises the following components: 40-60% epoxy resin, 0.5-3% heteropolyacid intercalated graphene oxide nano-inorganic filler, 10-20% epoxy curing agent, 0.3-1.5% dispersant, and 22.5-38.5% solvent. This invention utilizes the electrostatic bridging effect of cationic polyelectrolytes to obtain an electrostatically assembled material of heteropolyacid and graphene oxide, achieving a synergistic effect of physical barrier and chemical corrosion protection. Combined with the excellent adhesion and chemical corrosion resistance of epoxy resin, the prepared epoxy coating exhibits good density, strong adhesion, and excellent resistance to salt spray and acidic media corrosion, enabling it to adapt to the complex service environment of pipelines for extended periods.

Description

Technical Field

[0001] This invention belongs to the field of pipeline anti-corrosion coating technology, specifically relating to a heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating and its preparation method. Background Technology

[0002] As a core infrastructure for oil extraction and transportation, crude oil pipelines operate for extended periods in complex corrosive environments characterized by high temperatures, high pressures, high salinity, and sulfur and acid content. The inner walls of these pipelines come into contact with corrosive components in crude oil, while the outer walls are exposed to soil, atmosphere, or water. This makes them highly susceptible to electrochemical, chemical, and microbial corrosion, leading to pipe wall thinning, localized perforation, and leaks. These failures not only cause significant economic losses but also trigger serious environmental pollution and safety incidents. Therefore, developing high-performance anti-corrosion coatings is crucial for extending the service life of crude oil pipelines and ensuring their safe and stable operation.

[0003] Epoxy resin possesses excellent adhesion, chemical resistance, mechanical strength, and electrical insulation, making it one of the most widely used film-forming substrates for anti-corrosion coatings on crude oil pipelines. The epoxy groups in its molecular structure can cross-link with the curing agent, forming a dense three-dimensional network structure that can, to some extent, block the penetration of corrosive media. However, during the curing process, epoxy coatings develop micropores due to solvent evaporation and cross-linking shrinkage. These micropores provide channels for the penetration of corrosive media, leading to blistering and peeling of the coating after long-term service, resulting in anti-corrosion failure. Furthermore, epoxy coatings have poor toughness, making them prone to cracking during pipeline transportation or construction, further exacerbating corrosion problems.

[0004] Graphene oxide, as a novel two-dimensional nanomaterial, possesses an ultra-large specific surface area, excellent mechanical properties, and barrier properties. Adding it to epoxy coatings can utilize its layered structure to create a "maze effect," extending the penetration path of corrosive media and significantly improving the physical barrier performance of the coating. However, the strong van der Waals forces between graphene oxide layers make it prone to aggregation, leading to uneven dispersion in the epoxy system. This not only fails to realize its barrier advantages but may also become defects within the coating, reducing its mechanical and anti-corrosion properties.

[0005] Heteropolyacids are a class of polymetallic oxy-metal cluster compounds with well-defined structures, exhibiting excellent redox properties, atomically tunable structures, and superior thermal and chemical stability. The high-valence metal centers possess unbonded d orbitals, which can act as "electron libraries" to achieve reversible multi-electron transfer, demonstrating significant application potential in catalysis, corrosion protection, and other fields. Due to their excellent redox properties, heteropolyacids can induce the formation of dense passivation films on metal surfaces, inhibiting further oxidation reactions and achieving chemical corrosion protection, making them ideal anti-corrosion functional components. Heteropolyacids possess stable molecular structures and are stable under acidic conditions. The highly negatively charged heteropolyacid anions can bind to hydrogen ions under acidic conditions, exhibiting excellent acid resistance. Combining heteropolyacids with graphene oxide can achieve a synergistic effect of physical barrier and chemical corrosion protection, further enhancing the anti-corrosion performance of epoxy coatings. However, heteropoly acids carry a negative charge after dissolving in aqueous solution, and graphene oxide also carries a negative charge due to the presence of a large number of carboxyl and hydroxyl groups on its surface. There is an electrostatic repulsion between the two, resulting in poor compatibility. Heteropoly acids are difficult to disperse uniformly in the graphene oxide system and cannot effectively enter the interlayer of graphene oxide. As a result, the synergistic anti-corrosion effect of the composite system cannot be fully exerted, and it cannot meet the requirements of crude oil pipelines to resist complex corrosive environments for a long time.

[0006] To address the aforementioned issues, existing technologies often employ surface modification to improve the compatibility between graphene oxide and heteropolyacids. However, commonly used modifiers involve complex processes and high costs, hindering industrial production. Furthermore, some modifiers exhibit poor compatibility with epoxy resins, affecting the film-forming properties and adhesion of epoxy coatings. Polyelectrolytes, as ionicly conductive polymers, can interact with graphene oxide and heteropolyacids through electrostatic interactions, potentially serving as linkers to achieve effective composites between heteropolyacids and graphene oxide. However, different polyelectrolytes exhibit significant differences in charge density and molecular structure, meaning not all polyelectrolytes can achieve effective intercalation of heteropolyacids between graphene oxide layers. Moreover, for epoxy coating systems, it is crucial to select polyelectrolytes that possess good compatibility with epoxy resins, strong corrosion resistance, environmental friendliness, and controllable cost. Summary of the Invention

[0007] This invention addresses the problems of insufficient anti-corrosion performance of simple epoxy coatings, easy agglomeration of graphene oxide, poor compatibility between heteropolyacids, graphene oxide, and epoxy resin, and difficulty in achieving synergistic anti-corrosion effects in composite systems. It provides a heteropolyacid-intercalated graphene oxide-epoxy anti-corrosion coating and its preparation method. Using polydiallyldimethylammonium chloride, chitosan, and ε-polylysine as binders, a heteropolyacid-intercalated graphene oxide nano-inorganic filler is prepared through an electrostatic self-assembly strategy. This filler is then applied to epoxy anti-corrosion coatings for crude oil pipelines, overcoming the technical bottlenecks of existing epoxy anti-corrosion coatings.

[0008] The specific technical solution is as follows: The first objective of this invention is to provide a heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating, comprising the following components by weight percentage: 40-60% epoxy resin, 0.5-3% heteropolyacid intercalated graphene oxide nano-inorganic filler, 10-20% epoxy curing agent, 0.3-1.5% dispersant, and 22.5-38.5% solvent.

[0009] Furthermore, the heteropolyacid intercalated graphene oxide nano-inorganic filler is prepared by intercalating heteropolyacid anions into the interlayer of graphene oxide using a cationic polyelectrolyte as a linker and an electrostatic self-assembly strategy.

[0010] Furthermore, the cationic polyelectrolyte is one of polydiallyldimethylammonium chloride, chitosan, and ε-polylysine.

[0011] This invention selects epoxy resin as the film-forming substrate. Its excellent adhesion and chemical corrosion resistance ensure that the coating is tightly bonded to the crude oil pipeline substrate, resisting the erosion of complex corrosive media. Heteropolyacid intercalated graphene oxide nano-inorganic filler serves as a functional component. Through the electrostatic bridging effect of cationic polyelectrolytes, the heteropolyacid and graphene oxide are electrostatically assembled, solving the problems of agglomeration and compatibility, thereby exerting the synergistic effect of physical barrier and chemical corrosion protection between the two. The epoxy curing agent ensures that the epoxy resin is fully cross-linked, forming a dense three-dimensional network structure, further improving the density and mechanical strength of the coating. The dispersant can improve the dispersibility of the nano-inorganic filler in the epoxy system.

[0012] Furthermore, the heteropolyacid is a Keggin-type heteropolyacid, selected from one or more of phosphomolybdic acid, phosphotungstic acid, silicotungstic acid, and silicotomolybdic acid.

[0013] Heteropoly acids have a stable structure and excellent redox properties, and can form a dense passivation film on the metal surface, effectively inhibiting further corrosion of the metal. In addition, heteropoly acids have excellent acid resistance and can maintain a stable structure and are not easily hydrolyzed in strongly acidic solutions.

[0014] Furthermore, the graphene oxide is exfoliated graphene oxide with a sheet thickness of 0.5-2 nm.

[0015] Exfoliated graphene oxide has a larger specific surface area and better dispersibility. Its layered structure can form a dense physical barrier in epoxy coatings, extending the penetration path of corrosive media and improving the barrier performance of the coating against corrosive media.

[0016] Furthermore, the epoxy resin is a bisphenol A type epoxy resin, selected from one or a mixture of two of E-44 and E-51, with the mixing mass ratio being arbitrary.

[0017] Bisphenol A epoxy resins have good film-forming properties, mechanical strength, and corrosion resistance, making them a common substrate for epoxy anti-corrosion coatings for pipelines. The fluidity and mechanical properties of the coating can be adjusted according to construction requirements.

[0018] Furthermore, the epoxy curing agent is selected from one of polyamide curing agents and aliphatic amine curing agents; Polyamide curing agents and aliphatic amine curing agents have good compatibility with bisphenol A epoxy resins, and the curing reaction is mild. The cured coating has good toughness and adhesion, which can effectively avoid the problems of excessive brittleness and easy cracking of epoxy coatings.

[0019] Furthermore, the dispersant is one of polycarboxylate dispersants or polyethylene glycol dispersants.

[0020] Polycarboxylate dispersants and polyethylene glycol dispersants can be effectively adsorbed on the surface of nano-inorganic fillers, reducing the interaction forces between fillers and preventing agglomeration. At the same time, they have good compatibility with epoxy resins and do not affect the coating performance.

[0021] Furthermore, the mass ratio of the epoxy curing agent to the epoxy resin is 1:(3-6).

[0022] Furthermore, the solvent is a mixture of xylene and butanol, and the mass ratio of xylene to butanol is (2-6):1.

[0023] The mixed solvent of xylene and butanol can effectively dissolve epoxy resin, adjust the viscosity and evaporation rate of the coating, and avoid the coating sagging or uneven film formation caused by a single solvent.

[0024] Furthermore, the mass ratio of xylene to butanol is (3-5):1. This ratio allows for more complete dissolution of the epoxy resin, moderate coating viscosity, uniform evaporation rate, improved coating performance and coating film quality, and suitability for the industrial production needs of epoxy anti-corrosion coatings.

[0025] The second objective of this invention is to provide a method for preparing the above-mentioned heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating, comprising the following steps: S1. Preparation of heteropolyacid intercalated graphene oxide nanofillers Graphene oxide was added to deionized water and ultrasonically dispersed for 0.5-2 h to obtain a graphene oxide dispersion A with a mass concentration of 0.05-0.3%. A cationic polyelectrolyte solution B with a mass concentration of 0.3-2% was slowly added dropwise to the graphene oxide dispersion A, controlling the mass ratio of cationic polyelectrolyte to graphene oxide at (1-4):1. The mixture was stirred at a constant speed of 800-1200 r / min at 25-40℃ for 12-24 h to obtain a polyelectrolyte-modified graphene oxide dispersion C. A molar concentration of 0.01- A 0.1 mol / L heteropolyacid solution D was slowly added dropwise to a polyelectrolyte-modified graphene oxide dispersion C, with the mass ratio of heteropolyacid to graphene oxide controlled at (1-3):1. The mixture was stirred at a constant speed of 800-1200 r / min for 4-8 h. Subsequently, it was centrifuged at 8000-12000 r / min, washed alternately with deionized water and ethanol until the washing solution was neutral, dried under vacuum at 60-80℃, and ground to a particle size of 400-600 mesh to obtain the heteropolyacid-intercalated graphene oxide nano-inorganic filler. S2. Preparation of epoxy anti-corrosion coating Weigh the epoxy resin according to the mass fraction and add it to a dispersion device containing solvent. Stir at 500-1000 r / min for 10-20 min to obtain an epoxy resin solution. Then, add the weighed heteropolyacid intercalated graphene oxide nano-inorganic filler and dispersant to the epoxy resin solution. First, ultrasonically disperse for 30-60 min, then stir at high speed of 1200-2000 r / min for 2-4 h to obtain a uniform dispersion system. Slowly add the weighed epoxy curing agent to the above dispersion system and stir at 800-1200 r / min for 20-30 min. Vacuum defoaming is then performed for 5-10 min to obtain an epoxy anti-corrosion coating. S3, Preparation of epoxy anti-corrosion coating The pipeline substrate is pretreated, and an epoxy anti-corrosion coating is applied to the surface of the pretreated pipeline substrate by spraying, with the wet film thickness controlled at 60-150μm; the spraying pressure is 0.3-0.5MPa, and the spraying distance is 15-30cm; the coated substrate is then cured at 25-120℃ for 24-96h, and the heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating is obtained after complete curing.

[0026] In step S1, ultrasonic dispersion can effectively peel off the graphene oxide sheets, break up the agglomeration between the sheets, ensure uniform dispersion of graphene oxide, and guarantee the peeling effect.

[0027] In step S1, the cationic polyelectrolyte is one of polydiallyldimethylammonium chloride, chitosan, and ε-polylysine; wherein, when preparing the chitosan solution, acetic acid solution with a mass fraction of 1-2% needs to be added to aid dissolution and stirred until completely dissolved; polydiallyldimethylammonium chloride and ε-polylysine can be directly dissolved in deionized water; under acidic conditions, chitosan can form positively charged protonated amino groups, which facilitate electrostatic interaction with the negative charge on the surface of graphene oxide.

[0028] In step S1, the surface of graphene oxide contains a large number of carboxyl and hydroxyl groups, which are negatively charged, while the polyelectrolyte is positively charged. The two interact through electrostatic attraction, and the polyelectrolyte molecules are adsorbed on the surface of the graphene oxide sheet, modifying the surface of the graphene oxide and providing anchoring points for subsequent heteropolyacid intercalation.

[0029] In step S1, the heteropolyacid dissociates in the aqueous solution and carries a negative charge. It can interact electrostatically with the positively charged anchoring sites on the surface of polyelectrolyte-modified graphene oxide and insert itself into the interlayer of graphene oxide through electrostatic self-assembly to form a heteropolyacid intercalation structure. This effectively breaks the aggregation of graphene oxide sheets and realizes the electrostatic assembly of heteropolyacid and graphene oxide.

[0030] Furthermore, in step S1, after grinding and pulverizing, the material is sieved with a filter screen to remove large particles of impurities, ensuring that the particle size of the heteropolyacid intercalated graphene oxide nano-inorganic filler is uniform, and avoiding large particles of impurities from affecting the density and surface smoothness of the coating.

[0031] In step S2, vacuum defoaming can remove air bubbles from the coating, preventing defects such as pinholes and bubbles from appearing after the coating film is formed, and ensuring the density of the coating.

[0032] Furthermore, in step S3, the pretreatment includes the following steps: sanding with 400, 800 and 1200 grit sandpaper in sequence, washing with deionized water and ethanol until neutral, and finally drying at 80-100℃ for later use.

[0033] Pretreatment can remove impurities and oxide scale from the pipe surface, enhancing the adhesion between the coating and the substrate.

[0034] Furthermore, in step S3, during curing, the ambient humidity is controlled at 40-60% to avoid problems such as moisture return and blistering of the coating during the curing process.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The epoxy anti-corrosion coating of the present invention uses epoxy resin as the film-forming substrate, heteropolyacid intercalated graphene oxide nano-inorganic filler as the functional reinforcing component, and is prepared with epoxy curing agent, dispersant and solvent. The present invention solves the technical problems of easy agglomeration of graphene oxide in epoxy coating, poor dispersibility of heteropolyacid, and difficulty in exerting the synergistic anti-corrosion effect of the two. By utilizing the electrostatic bridging effect of cationic polyelectrolyte, a heteropolyacid and graphene oxide electrostatic assembly material is obtained, realizing the synergistic effect of physical barrier and chemical anti-corrosion. Combined with the excellent adhesion and chemical corrosion resistance of epoxy resin, the prepared epoxy coating has good density, strong adhesion, excellent resistance to salt spray and acidic media corrosion, and can be adapted to the complex service environment of pipelines for a long time. The preparation method is simple and controllable, suitable for large-scale industrial production, and can be widely used in pipeline anti-corrosion protection.

[0036] (2) The present invention adopts an electrostatic self-assembly strategy, using cationic polyelectrolytes as a linker, and realizes the intercalation of heteropolyacids between graphene oxide layers through electrostatic self-assembly, effectively breaking the aggregation of graphene oxide sheets, and solving the problem of poor compatibility between heteropolyacids, graphene oxide and epoxy resin, achieving uniform composite of the three and giving full play to the synergistic anti-corrosion effect.

[0037] (3) The heteropolyacid intercalated graphene oxide nano-inorganic filler prepared by the present invention achieves the synergistic effect of physical barrier, chemical corrosion protection and epoxy resin adhesion advantages: the graphene oxide sheets can form a dense physical barrier in the epoxy coating to block the penetration of corrosive media such as water, oxygen, salts and sulfur-containing compounds; the heteropolyacid anions can form a passivation film on the metal surface to inhibit the redox reaction of the metal, and the redox properties and acid resistance of the heteropolyacid can further improve the corrosion resistance of the coating; the epoxy resin coating has a strong adhesion to the pipeline substrate, avoiding coating peeling, and works synergistically with the nano-inorganic filler to enable the coating to resist the complex corrosive environment of crude oil pipelines for a long time.

[0038] (4) The preparation method of the present invention is simple and easy to implement, without the need for complex equipment and harsh reaction conditions. The electrostatic self-assembly intercalation process is mild and efficient. The preparation process of nano-inorganic fillers and epoxy anti-corrosion coatings can be scaled up. The coating spraying method is simple and has broad industrial application value.

[0039] (5) The epoxy anti-corrosion coating of the present invention not only has excellent corrosion resistance, but also good adhesion, toughness and durability. According to the test, the adhesion level of the coating to the crude oil pipeline substrate can reach level 1 (GB / T 9286-1998), the salt spray resistance time (neutral salt spray test, GB / T 10125-2021) is ≥600h, and the immersion time in acidic medium (20% hydrochloric acid solution) is greater than 144h. It can effectively extend the service life of crude oil pipelines, reduce pipeline maintenance costs, and reduce safety accidents and environmental pollution caused by corrosion leakage. Detailed Implementation

[0040] The principles and features of the present invention are described below with reference to examples. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0041] In the specific implementation, the polyamide curing agent 650 was purchased from Suzhou Senfida Chemical Co., Ltd., the aliphatic amine curing agent T-31 was purchased from Hubei Maidehao Biotechnology Co., Ltd., the polycarboxylate dispersant SN5040 and the polyethylene glycol dispersant PEG-1500 were both purchased from Sanda Chemical Co., Ltd., the exfoliated graphene oxide was purchased from Suzhou Carbonfeng Graphene Technology Co., Ltd., and the heteropolyacid compounds (phosphomolybdic acid, phosphotungstic acid, silicotungstic acid, silicotungstic acid) were purchased from Anhui Zesheng Technology Co., Ltd.

[0042] Example 1 A heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating comprises, by weight percentage: 45% bisphenol A epoxy resin E-44, 1% heteropolyacid intercalated graphene oxide nano-inorganic filler, 15% polyamide curing agent 650, 0.5% polycarboxylate dispersant SN5040, and 38.5% solvent.

[0043] The solvent is a mixture of xylene and butanol in a mass ratio of 4:1. The heteropolyacid intercalated graphene oxide nano-inorganic filler is prepared by intercalating phosphomolybdic acid into the interlayer of graphene oxide using polydiallyldimethylammonium chloride as a linker through an electrostatic self-assembly strategy. The graphene oxide is exfoliated graphene oxide with a sheet thickness of 0.5-1 nm.

[0044] A method for preparing a heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating includes the following steps: S1. Preparation of heteropolyacid intercalated graphene oxide nanofillers 0.5 g of graphene oxide was added to 1000 mL of deionized water and ultrasonically dispersed for 1 h to obtain a graphene oxide dispersion A with a mass concentration of 0.05%. 100 mL of a 2% polydiallyldimethylammonium chloride solution B was slowly added dropwise to graphene oxide dispersion A, controlling the mass ratio of polyelectrolyte polydiallyldimethylammonium chloride to graphene oxide at 4:1. The mixture was stirred at a constant speed of 1000 r / min at 30 °C for 12 h to obtain a polyelectrolyte-modified graphene oxide dispersion C. A 0.01 mol / L phosphomolybdic acid solution D was added... 100 mL was slowly added dropwise to the polyelectrolyte-modified graphene oxide dispersion C, and the mass ratio of phosphomolybdic acid to graphene oxide was controlled at 2:1. The mixture was stirred at 900 r / min for 6 h, then centrifuged at 10000 r / min. The mixture was washed multiple times with deionized water and ethanol until neutral, and then vacuum dried at 70 °C for 12 h. The mixture was then ground and sieved through a filter to a particle size of 500 mesh to obtain heteropolyacid intercalated graphene oxide nano-inorganic filler. S2. Preparation of epoxy anti-corrosion coating Weigh 45g of epoxy resin E-44 and add it to a dispersion device. Stir at 800r / min for 10min to completely dissolve the epoxy resin in the mixed solvent, obtaining an epoxy resin solution. Add 1g of heteropolyacid intercalated graphene oxide nano-inorganic filler and 0.5g of polycarboxylate dispersant SN5040 to the epoxy resin solution. First, ultrasonically disperse for 45min, then stir at 1200r / min for 2h to obtain a uniform dispersion system. Then, slowly add 15g of polyamide curing agent 650 to the dispersion system, stir at 1000r / min for 25min, and vacuum defoam for 8min to obtain an epoxy anti-corrosion coating. S3, Preparation of epoxy anti-corrosion coating The carbon steel pipe substrate was pretreated by sanding it sequentially with 400, 800, and 1200 grit sandpaper, washing it with deionized water and ethanol until neutral, and finally drying it at 80°C for later use. The pretreatment was to remove impurities and oxide scale from the pipe surface. The epoxy anti-corrosion coating prepared by S2 was applied to the pipe substrate surface by spraying at a pressure of 0.3 MPa and a distance of 20 cm, with the wet film thickness controlled at 120 μm. The coated substrate was then cured at room temperature for 24 h, and then cured at 80°C for 48 h. After complete curing, a heteropolyacid intercalated graphene oxide epoxy anti-corrosion coating was obtained, with the ambient humidity controlled at 40%.

[0045] Example 2 A heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating comprises, by weight percentage: 50% bisphenol A epoxy resin E-51, 2% heteropolyacid intercalated graphene oxide nano-inorganic filler, 12% aliphatic amine curing agent T-31, 0.8% polyethylene glycol dispersant PEG-1500, and 35.2% solvent.

[0046] The solvent is a mixture of xylene and butanol in a mass ratio of 3:1. The heteropolyacid intercalated graphene oxide nano-inorganic filler is prepared by intercalating phosphotungstic acid into the interlayer of graphene oxide using chitosan as a linker through an electrostatic self-assembly strategy. The graphene oxide is exfoliated graphene oxide with a sheet thickness of 0.5-1 nm.

[0047] A method for preparing a heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating includes the following steps: S1. Preparation of heteropolyacid intercalated graphene oxide nanofillers 1g of graphene oxide was added to 1000mL of deionized water and ultrasonically dispersed for 1.5h to obtain graphene oxide separation solution A with a mass concentration of 0.1%; chitosan solution B with a mass concentration of 0.8% (when preparing chitosan solution, acetic acid solution with a mass fraction of 1.8% needs to be added to aid dissolution, and stirred until completely dissolved) was added. 300 mL of polyelectrolyte chitosan to graphene oxide dispersion A was slowly added dropwise, and the mass ratio of polyelectrolyte chitosan to graphene oxide was controlled at 2:1. The mixture was stirred at 800 r / min at 35 °C for 15 h to obtain polyelectrolyte-modified graphene oxide dispersion C. 50 mL of 0.08 mol / L phosphotungstic acid solution D was slowly added dropwise to the above polyelectrolyte-modified graphene oxide dispersion C, and the mass ratio of phosphotungstic acid to graphene oxide was controlled at 3:1. The mixture was stirred at 1200 r / min for 7 h, then centrifuged at 11000 r / min. The mixture was washed multiple times with deionized water and ethanol until neutral, and vacuum dried at 75 °C for 12 h. The mixture was then ground and sieved through a filter to a particle size of 400 mesh to obtain heteropolyacid intercalated graphene oxide nano-inorganic filler. S2. Preparation of epoxy anti-corrosion coating Weigh 50g of epoxy resin E-51 and add it to a dispersion device. Stir at 1000r / min for 12min to completely dissolve the epoxy resin in the mixed solvent, obtaining an epoxy resin solution. Add 2g of heteropolyacid intercalated graphene oxide nano-inorganic filler and 0.8g of polyethylene glycol dispersant PEG-1500 to the epoxy resin solution. First, ultrasonically disperse for 60min, then stir at 1800r / min for 2.5h to obtain a uniform dispersion system. Then, slowly add 12g of aliphatic amine curing agent T-31 to the dispersion system, stir at 1200r / min for 20min, and vacuum defoam for 6min to obtain an epoxy anti-corrosion coating. S3, Preparation of epoxy anti-corrosion coating The carbon steel pipe substrate was pretreated by sanding it sequentially with 400, 800, and 1200 grit sandpaper, washing it with deionized water and ethanol until neutral, and finally drying it at 85°C for later use. This pretreatment was to remove impurities and oxide scale from the pipe surface. The epoxy anti-corrosion coating prepared by S2 was applied to the pipe substrate surface by spraying at a pressure of 0.3 MPa and a distance of 20 cm, with the wet film thickness controlled at 130 μm. The coated substrate was then cured at room temperature for 24 hours, followed by curing at 100°C for 48 hours. After complete curing, a heteropolyacid intercalated graphene oxide epoxy anti-corrosion coating was obtained, with the ambient humidity controlled at 55%.

[0048] Example 3 A heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating comprises, by weight percentage: 55% of a mixture of bisphenol A epoxy resins E-44 and E-51 (mass ratio 1:1), 3% of heteropolyacid intercalated graphene oxide nano-inorganic filler, 18% of polyamide curing agent 650, 1.5% of polycarboxylate dispersant SN5040, and 22.5% of solvent.

[0049] The mass ratio of E-44 to E-51 is 1:1; The solvent is a mixture of xylene and butanol in a mass ratio of 5:1. The heteropolyacid intercalated graphene oxide nano-inorganic filler is prepared by intercalating a mixture of silicotungstic acid and silicomolybdic acid (molar ratio 1:1) into the interlayer of graphene oxide through electrostatic self-assembly using ε-polylysine as a linker. The graphene oxide is exfoliated graphene oxide with a sheet thickness of 0.8-1.5 nm.

[0050] A method for preparing a heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating includes the following steps: S1. Preparation of heteropolyacid intercalated graphene oxide nanofillers 2g of graphene oxide was added to 1000mL of deionized water and ultrasonically dispersed for 2h to obtain a graphene oxide dispersion A with a mass concentration of 0.2%. 400mL of a 0.5% ε-polylysine solution B was slowly added dropwise to graphene oxide dispersion A, maintaining a mass ratio of ε-polylysine to graphene oxide of 1:1. The mixture was stirred at a constant speed of 1200r / min at 40℃ for 20h to obtain a polyelectrolyte-modified graphene oxide dispersion C. A mixed heteropolyacid solution D with a molar concentration of 0.02mol / L (a molar ratio of silicotungstic acid and silicomolybdic acid of 1:1) was added. 50 mL was slowly added dropwise to the polyelectrolyte-modified graphene oxide dispersion C, and the mass ratio of mixed heteropolyacid to graphene oxide was controlled at 1:1. The mixture was stirred at 1200 r / min for 8 h, then centrifuged at 12000 r / min. The mixture was washed multiple times with deionized water and ethanol until neutral, and then vacuum dried at 75 °C for 12 h. The mixture was then ground and sieved through a filter to a particle size of 600 mesh to obtain heteropolyacid-intercalated graphene oxide nano-inorganic filler. S2. Preparation of epoxy anti-corrosion coating Weigh 55g of epoxy resins E-44 and E-51 (mass ratio 1:1) and add them to a dispersion device. Stir at 600r / min for 20min to completely dissolve the epoxy resins in the mixed solvent, obtaining an epoxy resin solution. Add 3g of heteropolyacid intercalated graphene oxide nano-inorganic filler and 1.5g of polycarboxylate dispersant SN5040 to the epoxy resin solution. First, ultrasonically disperse for 60min, then stir at 2000r / min for 4h to obtain a uniform dispersion system. Then, slowly add 18g of polyamide curing agent 650 to the dispersion system, stir at 1200r / min for 28min, and vacuum defoam for 10min to obtain an epoxy anti-corrosion coating. S3, Preparation of epoxy anti-corrosion coating The carbon steel pipe substrate was pretreated by sanding it sequentially with 400, 800, and 1200 grit sandpaper, washing it with deionized water and ethanol until neutral, and finally drying it at 80°C for later use. The pretreatment was to remove impurities and oxide scale from the pipe surface. The epoxy anti-corrosion coating prepared by S2 was applied to the pipe substrate surface by spraying at a pressure of 0.4 MPa and a distance of 25 cm, with the wet film thickness controlled at 150 μm. The coated substrate was then cured at room temperature for 24 h, and then cured at 120°C for 48 h. After complete curing, a heteropolyacid intercalated graphene oxide epoxy anti-corrosion coating was obtained, with the ambient humidity controlled at 60%.

[0051] Example 4 A heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating comprises, by weight percentage: 48% bisphenol A epoxy resin E-44, 2.5% heteropolyacid intercalated graphene oxide nano-inorganic filler, 13% polyamide curing agent 650, 1.0% polyethylene glycol dispersant PEG-1500, and 35.5% solvent.

[0052] The solvent is a mixture of xylene and butanol in a mass ratio of 4:1. The heteropolyacid intercalated graphene oxide nano-inorganic filler is prepared by intercalating a mixture of phosphomolybdic acid and phosphotungstic acid (molar ratio 1:1) into the interlayer of graphene oxide through electrostatic self-assembly using polyallyldimethylammonium chloride as a linker. The graphene oxide is exfoliated graphene oxide with a sheet thickness of 0.5-2 nm.

[0053] A method for preparing a heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating is described in Example 3.

[0054] Example 5 A heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating comprises, by weight percentage: 60% bisphenol A epoxy resin E-51, 0.5% heteropolyacid intercalated graphene oxide nano-inorganic filler, 10% polyamide curing agent 650, 0.3% polyethylene glycol dispersant PEG-1500, and 29.2% solvent.

[0055] The solvent is a mixture of xylene and butanol in a mass ratio of 3:1. The heteropolyacid intercalated graphene oxide nano-inorganic filler is prepared by intercalating phosphomolybdic acid into the interlayer of graphene oxide through electrostatic self-assembly using ε-polylysine as a linker. The graphene oxide is exfoliated graphene oxide with a sheet thickness of 0.5-1 nm.

[0056] A method for preparing a heteropolyacid intercalated graphene oxide-epoxy anticorrosion coating is described in Example 2.

[0057] Comparative Example 1 An epoxy anti-corrosion coating for crude oil pipelines comprises the following components by weight percentage: 46% bisphenol A epoxy resin E-44, 15% polyamide curing agent 650, 0.5% polycarboxylate dispersant SN5040, and 38.5% solvent.

[0058] The solvent is a mixture of xylene and butanol in a mass ratio of 4:1.

[0059] A method for preparing an epoxy anti-corrosion coating for crude oil pipelines includes the following steps: S1. Preparation of epoxy anti-corrosion coating Weigh 46g of epoxy resin E-44 and add it to a dispersion device containing a mixed solvent. Stir at 800r / min for 10min to completely dissolve the epoxy resin and obtain an epoxy resin solution. Slowly add 0.5g of polycarboxylate dispersant SN5040 and 15g of polyamide curing agent 650 to the epoxy resin solution. Stir at 1000r / min for 25min and defoam under vacuum for 8min to obtain an epoxy anti-corrosion coating. S2. Preparation of epoxy anti-corrosion coating Pretreatment of the carbon steel crude oil pipeline substrate: The substrate was successively polished with 400, 800, and 1200 grit sandpaper, washed with deionized water and ethanol until neutral, and finally dried at 80℃ for later use. This pretreatment removed impurities and oxide scale from the pipeline surface. The anti-corrosion coating prepared by S1 was applied to the pretreated pipeline substrate surface by spraying at a pressure of 0.3 MPa and a distance of 20 cm, controlling the wet film thickness to 120 μm. The coated substrate was cured at room temperature for 24 hours, then cured at 80℃ for 48 hours. After complete curing, an epoxy anti-corrosion coating was obtained, with the ambient humidity controlled at 40%.

[0060] Comparative Example 2 A heteropolyacid epoxy anti-corrosion coating comprises, by weight percentage: 45% bisphenol A epoxy resin E-44, 1% heteropolyacid nano-inorganic filler, 15% polyamide curing agent 650, 0.5% polycarboxylate dispersant SN5040, and 38.5% solvent.

[0061] The solvent is a mixture of xylene and butanol in a mass ratio of 4:1. The heteropolyacid nano-inorganic filler is a phosphomolybdic acid heteropolyacid nano-inorganic filler.

[0062] A method for preparing a heteropoly acid epoxy anti-corrosion coating includes the following steps: S1. Preparation of epoxy anti-corrosion coating Weigh 45g of epoxy resin E-44 and add it to a dispersion device containing a mixed solvent. Stir at 800r / min for 10min to completely dissolve the epoxy resin and obtain an epoxy resin solution. Add 1g of phosphomolybdic acid heteropoly acid nano-inorganic filler and 0.5g of polycarboxylate dispersant SN5040 to the epoxy resin solution. First, ultrasonically disperse for 45min, then stir at 1200r / min for 2h to obtain a uniform dispersion system. Slowly add 15g of polyamide curing agent 650 to the dispersion system, stir at 1000r / min for 25min, and vacuum defoam for 8min to obtain an epoxy anti-corrosion coating. S2. Preparation of epoxy anti-corrosion coating The carbon steel crude oil pipeline substrate was pretreated by sanding it sequentially with 400, 800, and 1200 grit sandpaper, washing it with deionized water and ethanol until neutral, and finally drying it at 80°C for later use. The pretreatment was to remove impurities and oxide scale from the pipeline surface. The anti-corrosion coating prepared by S1 was applied to the pretreated pipeline substrate surface by spraying at a pressure of 0.3 MPa and a distance of 20 cm, with the wet film thickness controlled at 120 μm. The coated substrate was cured at room temperature for 24 h, and then cured at 80°C for 48 h. After complete curing, a heteropoly acid epoxy anti-corrosion coating was obtained, with the ambient humidity controlled at 40%.

[0063] Comparative Example 3 An epoxy anti-corrosion coating for crude oil pipelines using graphene oxide comprises the following components by weight percentage: 45% bisphenol A epoxy resin E-44, 1% graphene oxide nano-inorganic filler, 15% polyamide curing agent 650, 0.5% polycarboxylate dispersant SN5040, and 38.5% solvent.

[0064] The solvent is a mixture of xylene and butanol in a mass ratio of 4:1. The graphene oxide nano-inorganic filler is exfoliated graphene oxide with a sheet thickness of 0.5-1 nm.

[0065] A method for preparing a heteropoly acid epoxy anti-corrosion coating includes the following steps: S1. Preparation of epoxy anti-corrosion coating Weigh 45g of epoxy resin E-44 and add it to a dispersion device containing a mixed solvent. Stir at 800r / min for 10min to completely dissolve the epoxy resin and obtain an epoxy resin solution. Add 1g of graphene oxide nano-inorganic filler and 0.5g of polycarboxylate dispersant SN5040 to the epoxy resin solution. First, ultrasonically disperse for 45min, then stir at 1200r / min for 2h to obtain a uniform dispersion system. Slowly add 15g of polyamide curing agent 650 to the dispersion system, stir at 1000r / min for 25min, and vacuum defoam for 8min to obtain an epoxy anti-corrosion coating. S2. Preparation of epoxy anti-corrosion coating The carbon steel crude oil pipeline substrate was pretreated by sanding it sequentially with 400, 800, and 1200 grit sandpaper, washing it with deionized water and ethanol until neutral, and finally drying it at 80°C for later use. This pretreatment removed impurities and oxide scale from the pipeline surface. The anti-corrosion coating was then applied to the pretreated pipeline substrate surface by spraying at a pressure of 0.3 MPa and a distance of 20 cm, controlling the wet film thickness to 120 μm. The coated substrate was then cured at room temperature for 24 hours, followed by curing at 80°C for 48 hours. After complete curing, a graphene oxide epoxy anti-corrosion coating was obtained, with the ambient humidity controlled at 40%.

[0066] test: To verify the technical effectiveness of the anti-corrosion coating provided by this invention, system performance tests were conducted on the epoxy anti-corrosion coating materials prepared in each embodiment and comparative example. The test methods are as follows: Adhesion test: GB / T 9286-1998 "Cross-cut test for paint and varnish films"; Neutral salt spray test: GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test"; Acid resistance test: Immersion time in acid-resistant medium (20% hydrochloric acid solution) is greater than 144 hours.

[0067] The test data for each embodiment and comparative example are shown in Table 1 below.

[0068] Table 1. Performance test results of epoxy anti-corrosion coatings in each embodiment and comparative example.

[0069] The epoxy anti-corrosion coating materials prepared in each embodiment and comparative example were immersed in a 3.5wt% NaCl solution for 72 hours. Based on the Tafel test results, the corrosion rate of the pipeline substrate was calculated. The specific test results are shown in Table 2 below.

[0070] Table 2. Corrosion rate results of epoxy anti-corrosion coatings in each embodiment and comparative example.

[0071] As shown in Table 1, the epoxy anti-corrosion coatings prepared by the method described in this invention in Examples 1-5 exhibit excellent corrosion protection performance. Adhesion all reached Grade 1, and the neutral salt spray test time was no less than 600 hours. No peeling or corrosion was observed in the acid resistance test. In contrast, Comparative Example 1 (without heteropolyacid intercalated graphene oxide filler) only had a neutral salt spray tolerance time of 150 hours, and peeling and pitting occurred in the acid resistance test, indicating that the absence of heteropolyacid intercalated graphene oxide filler significantly reduces the protective performance of the coating. Comparative Example 2 (with heteropolyacid filler) showed a small amount of coating peeling in the acid resistance test, while Comparative Example 3 (with graphene oxide filler) showed a small amount of pitting, indicating that a single functional component cannot simultaneously meet the dual protection requirements of physical barrier and chemical passivation. The acid resistance tests of the comparative examples and examples show that the introduction of heteropolyacid enhances the acid resistance of the coating, resisting corrosion of crude oil pipelines under strong acid conditions.

[0072] According to the corrosion rate data in Table 2, the corrosion rates of Examples 1-5 were significantly lower than those of the comparative examples. The absence of graphene inorganic filler in Comparative Example 2 and the absence of heteropolyacid inorganic filler in Comparative Example 3 both increased the corrosion rate, while the combined absence of both in Comparative Example 1 resulted in a significantly increased corrosion rate (1.9 × 10⁻⁶). -5 (mm / a). The above results indicate that graphene oxide, through the "maze effect" formed by its two-dimensional sheets, extends the diffusion path of corrosive media, thereby enhancing the physical barrier performance of the coating. Heteropolyacids, utilizing their redox properties and stability under acidic conditions, induce the formation of a dense passivation film on the metal surface, protecting the metal from the direct effects of corrosion, thus achieving chemical corrosion protection. Using cationic polyelectrolytes as binders, the multi-acid intercalated graphene oxide nano-inorganic filler prepared through an electrostatic assembly strategy not only solves the problem of poor compatibility between heteropolyacids and graphene oxide in epoxy resin, but also achieves a synergistic effect of physical barrier and chemical corrosion protection, fully demonstrating that the corrosion protection performance of the composite of heteropolyacids and graphene oxide is significantly improved.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating, characterized in that, By weight percentage, it comprises the following components: 40-60% epoxy resin, 0.5-3% heteropolyacid intercalated graphene oxide nano-inorganic filler, 10-20% epoxy curing agent, 0.3-1.5% dispersant, and 22.5-38.5% solvent.

2. The heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating according to claim 1, characterized in that, The heteropolyacid intercalated graphene oxide nano-inorganic filler is prepared by intercalating heteropolyacid anions into the interlayer of graphene oxide using a cationic polyelectrolyte as a linker and an electrostatic self-assembly strategy.

3. The heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating according to claim 2, characterized in that, The cationic polyelectrolyte is one of polydiallyldimethylammonium chloride, chitosan, and ε-polylysine.

4. The heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating according to claim 2, characterized in that, The heteropolyacid is a Keggin-type heteropolyacid, selected from one or more of phosphomolybdic acid, phosphotungstic acid, silicotungstic acid, and silicotomolybdic acid.

5. The heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating according to claim 2, characterized in that, The graphene oxide is exfoliated graphene oxide with a sheet thickness of 0.5-2 nm.

6. The heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating according to claim 1, characterized in that, The epoxy resin is a bisphenol A type epoxy resin, selected from one or a mixture of two of E-44 and E-51; the epoxy curing agent is selected from one of polyamide curing agents and aliphatic amine curing agents; the dispersant is one of polycarboxylate dispersants and polyethylene glycol dispersants.

7. The heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating according to claim 1, characterized in that, The mass ratio of the epoxy curing agent to the epoxy resin is 1:(3-6).

8. The heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating according to claim 1, characterized in that, The solvent is a mixture of xylene and butanol, and the mass ratio of xylene to butanol is (2-6):

1.

9. A method for preparing a heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Preparation of heteropolyacid intercalated graphene oxide nanofillers Graphene oxide was added to deionized water and ultrasonically dispersed for 0.5-2 h to obtain a graphene oxide dispersion A with a mass concentration of 0.05-0.3%. A cationic polyelectrolyte solution B with a mass concentration of 0.3-2% was added dropwise to the graphene oxide dispersion A, controlling the mass ratio of cationic polyelectrolyte to graphene oxide at (1-4):

1. The mixture was stirred at a constant speed of 800-1200 r / min at 25-40℃ for 12-24 h to obtain a polyelectrolyte-modified graphene oxide dispersion C. A molar concentration of 0.01- A 0.1 mol / L heteropolyacid solution D was added dropwise to a polyelectrolyte-modified graphene oxide dispersion C, with the mass ratio of heteropolyacid to graphene oxide controlled at (1-3):

1. The mixture was stirred at a constant speed of 800-1200 r / min for 4-8 h. Subsequently, it was centrifuged at 8000-12000 r / min, washed alternately with deionized water and ethanol until the washing solution was neutral, dried under vacuum at 60-80℃, and ground to a particle size of 400-600 mesh to obtain the heteropolyacid-intercalated graphene oxide nano-inorganic filler. S2. Preparation of epoxy anti-corrosion coating Weigh the epoxy resin according to the mass fraction and add it to a dispersion device containing solvent. Stir at 500-1000 r / min for 10-20 min to obtain an epoxy resin solution. Then, add the weighed heteropolyacid intercalated graphene oxide nano-inorganic filler and dispersant to the epoxy resin solution. First, ultrasonically disperse for 30-60 min, then stir at 1200-2000 r / min for 2-4 h to obtain a uniform dispersion system. Add the weighed epoxy curing agent to the above dispersion system and stir at 800-1200 r / min for 20-30 min. Vacuum defoaming is then performed for 5-10 min to obtain an epoxy anti-corrosion coating. S3, Preparation of epoxy anti-corrosion coating The pipeline substrate is pretreated, and an epoxy anti-corrosion coating is applied to the surface of the pretreated pipeline substrate by spraying, with the wet film thickness controlled at 60-150μm; the spraying pressure is 0.3-0.5MPa, and the spraying distance is 15-30cm; the coated substrate is then cured at 25-120℃ for 24-96h, and the heteropolyacid intercalated graphene oxide-epoxy anti-corrosion coating is obtained after complete curing.

10. The preparation method according to claim 9, characterized in that, In step S3, the ambient humidity is controlled at 40-60% during curing.

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