Anticorrosive coating for oil well pipe and preparation method thereof

Abstract

The present invention relates to the technical field of anticorrosive coatings, and in particular to an anticorrosive coating for oil well pipes and a preparation method thereof, comprising the following raw materials in parts by mass: 40-50 parts of phenolic epoxy resin, 10-15 parts of modified graphene, 1-5 parts of aliphatic amine curing agent, 5-10 parts of reactive diluent, and 5-10 parts of organic solvent; the preparation method of the modified graphene comprises the following steps: A1: preparing a Schif base complex by reacting 3,5-diaminopyrazole and salicylaldehyde; A2: preparing an isocyanate graphene suspension; A3: adding 1H,1H-heptafluorobutylamine and Schif base complex to the obtained isocyanate graphene suspension, stirring and reacting at 30-50°C for 3-5h, filtering, washing, and drying to obtain a modified intermediate; A4: reacting glycidol with the modified intermediate. The anticorrosive coating prepared by the present invention has high bonding strength with oil well pipes, and effectively blocks the contact between corrosive media and metal oil well pipes.

Description

Technical Field

[0001] The invention relates to the technical field of anti-corrosion coatings, and in particular to an anti-corrosion coating for oil well pipes and a preparation method thereof. Background Art

[0002] Oil well pipe, also known as petroleum special pipe, is the foundation of the oil industry. It mainly includes casing, tubing and drill string components (drill pipe, drill collar, kelly, etc.), which are used to transport liquid or gaseous substances such as oil and natural gas. In recent years, with the continuous exploitation of oil and gas fields towards deep wells, ultra-deep wells and areas with harsh geological environments, higher requirements have been placed on the service performance of oil well pipes. It is reported that more than 30% of the world's oil and gas fields contain hydrogen sulfide gas. Hydrogen sulfide, as an acidic corrosive gas, can corrode oil and gas field equipment. Therefore, in order to meet operational needs, various oil well pipes resistant to hydrogen sulfide corrosion have emerged in an endless stream. For example: Patent CN201911365938.2 claims protection for a high-strength oil well pipe steel resistant to hydrogen sulfide corrosion and its preparation method, Patent CN202110010761.5 claims protection for a medium-carbon low-alloy high-strength oil well pipe resistant to hydrogen sulfide corrosion, Patent CN202211446521.0 claims protection for a high-grade oil well pipe resistant to hydrogen sulfide corrosion and its preparation method. However, in addition to improving the corrosion resistance of the oil well pipe itself, the hydrogen sulfide resistance of the oil well pipe can also be improved by coating its surface with anti-corrosion coatings, and the construction and maintenance costs are lower.

[0003] At present, the protective coatings for oil well pipes include epoxy-silicone resin, polyurethane coating, polyaniline (PANI) resin coating, fluorocarbon coating, phenolic resin, etc. For example, patent CN201510681866.8 discloses an anti-corrosion coating for the inner wall of an oil pipe and an oil pipe with an inner wall sprayed with an anti-corrosion coating, including component A and component B, specifically including the following components in mass ratio: component A includes modified phenolic resin, mixed solvent, additives and auxiliary materials, and the mass ratio of modified phenolic resin: mixed solvent: additives: auxiliary materials is 80-90: 5-15: 1-3: 0.5-2; wherein the mixed solvent includes xylene and butanone, and the additives include defoaming agent, anti-sagging agent and The film-forming aid comprises heavy calcium carbonate, kaolin and titanium dioxide; the B component comprises an accelerator and a solvent; the accelerator is a mixture of CYD-128 epoxy resin and bisphenol A, and the solvent is butanone; the mass ratio of the CYD-128 epoxy resin and bisphenol A is 2-6:2-5; the mass ratio of the A component: the B component is 3-7:0.5-2. The protective coating has the unique advantages of high temperature resistance and strong penetration resistance, and can be used for a long time in weak acid and weak alkali environments, especially in the presence of H2S, CO 2. It will play its unique advantages in special wells with high concentrations; for example, patent CN202210451607.6 discloses a corrosion-resistant and erosion-resistant surface protection method for oil well packers, in which epoxy-silicone modified anti-corrosion coatings and fluorocarbon anti-corrosion coatings are sprayed on the surface of metal components of oil well packers in sequence, wherein the epoxy-silicone modified anti-corrosion coating comprises the following raw material components in parts by weight: 200-280 parts of epoxy-silicone resin, 50-80 parts of carbon fiber, 60-90 parts of carbon fiber felt, 30-60 parts of aluminum oxide, 30-60 parts of titanium oxide; the fluorocarbon anti-corrosion coating includes the following raw material components in parts by weight: 300-450 parts of polytrifluoroethylene-based resin, 20-35 parts of graphene oxide, and 60-73 parts of silicon dioxide. The bottom layer (phosphate ceramic membrane), the middle layer (epoxy-silicone modified anti-corrosion coating) and the outer protective layer (fluorocarbon anti-corrosion coating) are used to improve the corrosion resistance of the metal surface, extend the service life of the packer, reduce the risk of packer failure, and reduce the cost of oil well maintenance and mining.

[0004] However, due to the limited bonding strength between organic anti-corrosion coatings and metal substrates, fillers in the anti-corrosion coatings are prone to swelling in high humidity or high pressure environments, forming corrosion channels, causing the anti-corrosion coatings to fail and become difficult to serve for a long time, thereby losing their resistance to hydrogen sulfide corrosion. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide an anti-corrosion coating for oil well pipes and a preparation method thereof, so as to solve the problem that the existing anti-corrosion coating is not firmly bonded to the substrate and cannot resist hydrogen sulfide corrosion for a long time.

[0006] Based on the above purpose, the present invention provides an anti-corrosion coating for oil well pipes, comprising the following raw materials by weight: 40-50 parts of phenolic epoxy resin, 10-15 parts of modified graphene, 1-5 parts of fatty amine curing agent, 5-10 parts of active diluent, and 5-10 parts of organic solvent;

[0007] The preparation method of the modified graphene comprises the following steps:

[0008] A1: Add 3,5-diaminopyrazole and salicylaldehyde to anhydrous methanol, stir to dissolve, then drop NaHCO3 solution, stir evenly, react at 40-60℃ for 6-12h, cool to 10-15℃, filter, recrystallize with anhydrous ethanol, centrifuge, and vacuum dry to obtain salicylaldehyde condensed with 3,5-diaminopyrazole Schif base complex;

[0009] The reaction equation is as follows:

[0010] ;

[0011] A2: Add nano-graphene oxide to an ethanol aqueous solution, stir and disperse, then add an isocyanate silane coupling agent, stir and react at 25-35°C for 1-2h to obtain an isocyanate graphene suspension;

[0012] A3: Add 1H,1H-heptafluorobutylamine and salicylaldehyde 3,5-diaminopyrazole Schif base complex to the obtained isocyanate graphene suspension, stir and react at 30-50°C for 3-5h, filter, wash and dry to obtain a modified intermediate;

[0013] A4: Add propylene oxide to anhydrous acetone, stir evenly, then add the obtained modified intermediate, mix evenly, then drop dibutyltin dilaurate, first stir and react at 50-55°C for 3-5h, then stir and react at 60-80°C for 2-3h to obtain modified graphene.

[0014] Furthermore, the dosage ratio of the 3,5-diaminopyrazole, salicylaldehyde, anhydrous methanol, NaHCO3 solution, and anhydrous ethanol is 10mmol:10mmol:30mL:(2-3)mL:15mL.

[0015] Furthermore, the concentration of the NaHCO3 solution is 0.5-1M.

[0016] Furthermore, the concentration of the ethanol aqueous solution is 50-70wt%.

[0017] Furthermore, the isocyanate silane coupling agent is at least selected from 3-isocyanate propyl trimethoxy silane, 3-isocyanate propyl triethoxy silane, 3-isocyanate propyl methyl dimethoxy silane or 3-isocyanate propyl methyl diethoxy silane.

[0018] Furthermore, the mass ratio of the nano-graphene oxide, ethanol aqueous solution, isocyanate silane coupling agent, 1H,1H-heptafluorobutylamine, salicylaldehyde 3,5-diaminopyrazole Schif base complex, glycidol, anhydrous acetone, and dibutyltin dilaurate is 1:(10-15):(0.3-0.5):(0.05-0.15):(0.1-0.2):(0.1-0.2):(2-3):(0.01-0.03).

[0019] Furthermore, the fatty amine curing agent is at least one selected from hexylene diamine, diethylene triamine and triethylene tetramine.

[0020] Furthermore, the active diluent is at least one selected from ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, and 1,6-hexanediol diglycidyl ether.

[0021] Furthermore, the organic solvent is at least one selected from dimethylformamide, acetone and cyclohexanone.

[0022] The present invention also provides a method for preparing the above-mentioned anti-corrosion coating for oil well tubulars, comprising the following steps:

[0023] S1: After the phenolic epoxy resin and the modified graphene are evenly mixed, the active diluent is added, and the mixture is evenly stirred to obtain component A;

[0024] S2: Add the fatty amine curing agent into the organic solvent, stir and dissolve, and obtain component B;

[0025] S3: Add component B to component A, stir and disperse at high speed under low temperature conditions of 10-20°C, and use immediately to obtain the anti-corrosion coating.

[0026] Beneficial effects of the present invention:

[0027] The anti-corrosion coating prepared by the present invention has high bonding strength with oil well pipes, can serve for a long time in high humidity, high pressure or high concentration H2S environment, prevents the contact between corrosive media and metal oil well pipes, and can effectively inhibit H2S, CO2 and Cl - It can prevent the corrosion of oil and gas pipelines and realize the anti-corrosion and protection of oil well pipes.

[0028] The present invention utilizes -NH2 on 1H,1H-heptafluorobutylamine and salicylaldehyde 3,5-diaminopyrazole Schif base complex to undergo nucleophilic addition reaction with -NCO on the surface of isocyanate-treated graphene, and then cross-grafts the 1H,1H-heptafluorobutylamine and salicylaldehyde 3,5-diaminopyrazole Schif base complex on the graphene surface, and self-assembles to form a functional small molecule structure grafted on both sides of the graphene oxide sheet. 1H,1H-heptafluorobutylamine connects super-hydrophobic organic fluorine molecular chains to the graphene oxide sheet, and in terms of spatial structure, forms a hydrophobic and water-blocking protective effect on the graphene, thereby avoiding the swelling effect of the graphene under high humidity conditions, and the introduction of the salicylaldehyde 3,5-diaminopyrazole Schif base complex improves the in-situ "anchoring" effect of graphene particles on the surface of oil well metal pipes. The pyrazole ring and Schiff base structure in the grafted complex react with the copper, nickel, chromium, manganese and other metal ions with empty orbitals on the surface of the oil well pipe to form a coordination complex reaction, thereby fixing the modified graphene on the surface of the oil well pipe, improving the bonding strength between the anti-corrosion coating and the oil well pipe, and preventing the coating peeling problem caused by high pressure conditions. At the same time, the enhanced crystalline inner film formed by the grafted complex on the graphene layer and the oil well pipe prevents the corrosion of hydrogen sulfide, and the constructed Schiff base-metal coordination bond double network system also has a strong self-repairing effect, which can realize the self-healing of the anti-corrosion coating, and the organic fluorine between the graphene and the oil well pipe also brings waterproof and hydrophobic effects to the oil well pipe, further improving the anti-corrosion effect, and realizing that the oil well pipe can still serve for a long time under high humidity, high pressure, high salt or high concentration of hydrogen sulfide conditions.

[0029] Surprisingly, the modified graphene has a significant antibacterial effect on sulfate-reducing bacteria that are widely present in oil and gas wells and oil fields, helps to inhibit the generation of hydrogen sulfide corrosion gas, and inhibits the growth of sulfate-reducing bacteria on the surface of oil well pipes, thereby inhibiting the corrosion of sulfate-reducing bacteria on oil well pipes. Considering its antibacterial mechanism, the possible reason is that the pyrazole ring derivatives and Schif bases in the complex grafted on the modified graphene have a synergistic effect on resistance to sulfate-reducing bacteria.

[0030] The present invention further grafts glycidol on the surface of graphene, utilizes the reaction of -OH in glycidol with -NCO on the surface of isocyanate-treated graphene, "grafts" epoxy groups on the surface of graphene, and under the action of aliphatic amine curing agent, stably embeds the modified graphene in the phenolic epoxy resin coating system, and helps the modified graphene to play a "maze" effect and network structure in the anti-corrosion coating, thereby improving the protective effect of the coating in a high concentration of H2S environment. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0032] The present invention provides an anti-corrosion coating for oil well tubulars according to an embodiment, comprising the following raw materials in parts by weight: 40-50 parts of phenolic epoxy resin, 10-15 parts of modified graphene, 1-5 parts of fatty amine curing agent, 5-10 parts of active diluent, and 5-10 parts of organic solvent;

[0033] The preparation method of the modified graphene comprises the following steps:

[0034] A1: Add 3,5-diaminopyrazole and salicylaldehyde to anhydrous methanol, stir to dissolve, then drop 0.5-1M NaHCO3 solution, stir evenly, react at 40-60℃ for 6-12h, cool to 10-15℃, filter, recrystallize with anhydrous ethanol, centrifuge, and vacuum dry to obtain salicylaldehyde condensed with 3,5-diaminopyrazole Schif base complex;

[0035] In one embodiment, the usage ratio of 3,5-diaminopyrazole, salicylaldehyde, anhydrous methanol, NaHCO3 solution, and anhydrous ethanol is 10mmol:10mmol:30mL:(2-3)mL:15mL;

[0036] The reaction equation is as follows:

[0037] ;

[0038] A2: Add nano-graphene oxide to 50-70wt% ethanol aqueous solution, stir and disperse, add isocyanate silane coupling agent, stir and react at 25-35°C for 1-2h to obtain isocyanate graphene suspension;

[0039] In one embodiment, the isocyanate silane coupling agent is at least one selected from 3-isocyanate propyl trimethoxy silane, 3-isocyanate propyl triethoxy silane, 3-isocyanate propyl methyl dimethoxy silane or 3-isocyanate propyl methyl diethoxy silane;

[0040] In this process, the surface of nano-graphene oxide is modified by using an isocyanate silane coupling agent, so that the surface of graphene oxide contains a large number of -NCO active groups, which prepares for further modification. At the same time, the surface modification of the isocyanate silane coupling agent also helps to improve the dispersibility and compatibility of graphene oxide, reduce agglomeration, and is conducive to reducing the interface defects and surface defects of nano-graphene oxide, thereby improving its binding performance and wear resistance in anti-corrosion coatings.

[0041] A3: Add 1H,1H-heptafluorobutylamine and salicylaldehyde 3,5-diaminopyrazole Schif base complex to the obtained isocyanate graphene suspension, stir and react at 30-50°C for 3-5h, filter, wash and dry to obtain a modified intermediate;

[0042] In this process, -NH2 on the Schif base complex of 1H,1H-heptafluorobutylamine and salicylaldehyde 3,5-diaminopyrazole is used to undergo a nucleophilic addition reaction with -NCO on the surface of isocyanate-treated graphene, and then the 1H,1H-heptafluorobutylamine and salicylaldehyde 3,5-diaminopyrazole Schif base complex is cross-grafted on the graphene surface to self-assemble into a functional small molecule structure grafted on both sides of the graphene oxide sheet. 1H,1H-heptafluorobutylamine connects super-hydrophobic organic fluorine molecular chains to the graphene oxide sheet, forming a hydrophobic and water-blocking protective effect on the graphene in terms of spatial structure, thereby avoiding the swelling of graphene under high humidity conditions. The introduction of the Schif base complex of salicylaldehyde 3,5-diaminopyrazole improves the in-situ "anchoring" of graphene particles on the surface of oil well metal pipes. "The pyrazole ring and Schiff base structure in the grafted complex react with the copper, nickel, chromium, manganese and other metal ions with empty orbitals on the surface of the oil well pipe to form a coordination complex, thereby fixing the modified graphene on the surface of the oil well pipe, improving the bonding strength between the anti-corrosion coating and the oil well pipe, and preventing the coating peeling problem caused by high pressure conditions. At the same time, the enhanced crystalline inner film formed by the grafted complex on the graphene layer and the oil well pipe prevents the corrosion of hydrogen sulfide, and the constructed Schiff base-metal coordination bond double network system also has a strong self-repairing effect, which can realize the self-healing of the anti-corrosion coating, and the organic fluorine between the graphene and the oil well pipe also brings waterproof and hydrophobic effects to the oil well pipe, further improving the anti-corrosion effect, and realizing that the oil well pipe can still serve for a long time under high humidity, high pressure, high salt or high concentration of hydrogen sulfide conditions.

[0043] Surprisingly, the modified graphene has a significant antibacterial effect on sulfate-reducing bacteria that are widely present in oil and gas wells and oil fields containing hydrogen sulfide, which helps to inhibit the generation of hydrogen sulfide corrosive gas and inhibit the growth of sulfate-reducing bacteria on the surface of oil well pipes, thereby inhibiting the corrosion of sulfate-reducing bacteria on oil well pipes. Considering its antibacterial mechanism, the possible reason is that the pyrazole ring derivatives and Schif bases in the complex grafted on the modified graphene have a synergistic effect on resistance to sulfate-reducing bacteria.

[0044] A4: Add propylene oxide to anhydrous acetone, stir evenly, then add the obtained modified intermediate, mix evenly, then drop dibutyltin dilaurate, first stir and react at 50-55°C for 3-5h, then stir and react at 60-80°C for 2-3h to obtain modified graphene;

[0045] In one embodiment, the mass ratio of nano-graphene oxide, ethanol aqueous solution, isocyanate silane coupling agent, 1H,1H-heptafluorobutylamine, salicylaldehyde 3,5-diaminopyrazole Schif base complex, glycidol, anhydrous acetone, and dibutyltin dilaurate is 1:(10-15):(0.3-0.5):(0.05-0.15):(0.1-0.2):(0.1-0.2):(2-3):(0.01-0.03);

[0046] In this process, the -OH in glycidol reacts with the -NCO on the surface of isocyanate-treated graphene to "graft" epoxy groups on the graphene surface. Under the action of aliphatic amine curing agent, the modified graphene is stably embedded in the phenolic epoxy resin coating system, which helps the modified graphene to play a "maze" effect and network structure in the anti-corrosion coating, thereby improving the protective effect of the coating in a high-concentration H2S environment.

[0047] In one embodiment, the fatty amine curing agent is at least one selected from hexamethylenediamine, diethylenetriamine, and triethylenetetramine;

[0048] In one embodiment, the reactive diluent is at least one selected from ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, and 1,6-hexanediol diglycidyl ether;

[0049] In one embodiment, the organic solvent is at least one selected from dimethylformamide, acetone, and cyclohexanone.

[0050] The method for preparing the anti-corrosion coating for oil well tubular goods of this embodiment comprises the following steps:

[0051] S1: After the phenolic epoxy resin and the modified graphene are evenly mixed, the active diluent is added, and the mixture is evenly stirred to obtain component A;

[0052] S2: Add the fatty amine curing agent into the organic solvent, stir and dissolve, and obtain component B;

[0053] S3: Add component B to component A, stir and disperse at high speed under low temperature conditions of 10-20°C, and use immediately to obtain the anti-corrosion coating.

[0054] Example 1

[0055] A method for preparing an anti-corrosion coating for oil well tubulars comprises the following steps:

[0056] S1: Preparation of modified graphene:

[0057] S101: Add 3,5-diaminopyrazole and salicylaldehyde to anhydrous methanol, stir to dissolve, then drop 0.5M NaHCO3 solution, stir evenly, react at 40°C with stirring for 6h, cool to 10°C, filter, and recrystallize with anhydrous ethanol. Centrifuge and vacuum dry to obtain salicylaldehyde condensed with 3,5-diaminopyrazole Schif base complex; wherein the amount ratio of 3,5-diaminopyrazole, salicylaldehyde, anhydrous methanol, 0.5M NaHCO3 solution, and anhydrous ethanol is 10mmol:10mmol:30mL:2mL:15mL;

[0058] S102: adding nano-graphene oxide to a 50 wt % ethanol aqueous solution, stirring and dispersing, adding 3-isocyanate propyltrimethoxysilane, stirring and reacting at 25° C. for 1 h, to obtain an isocyanate graphene suspension;

[0059] S103: adding 1H,1H-heptafluorobutylamine and salicylaldehyde 3,5-diaminopyrazole Schif base complex to the obtained isocyanate graphene suspension, stirring and reacting at 40° C. for 3 h, filtering, washing and drying to obtain a modified intermediate;

[0060] S104: Add propylene oxide to anhydrous acetone, stir evenly, then add the obtained modified intermediate, mix evenly, then drop dibutyltin dilaurate, first stir and react at 50° C. for 3 h, then stir and react at 60° C. for 2 h, to obtain modified graphene;

[0061] In S102-S104, the mass ratio of nano-graphene oxide, 50wt% ethanol aqueous solution, 3-isocyanatepropyltrimethoxysilane, 1H,1H-heptafluorobutylamine, salicylaldehyde 3,5-diaminopyrazole Schif base complex, glycidol, anhydrous acetone, and dibutyltin dilaurate is 1:10:0.3:0.1:0.1:0.1:2:0.01;

[0062] S2: Prepare the following materials in parts by mass: 40 parts of phenolic epoxy resin, 10 parts of modified graphene, 2 parts of fatty amine curing agent diethylenetriamine, 5 parts of active diluent ethylene glycol diglycidyl ether, and 5 parts of organic solvent acetone;

[0063] S3: After the phenolic epoxy resin and the modified graphene are evenly mixed, an active diluent ethylene glycol diglycidyl ether is added, and the mixture is evenly stirred to obtain component A;

[0064] S4: Adding a fatty amine curing agent diethylenetriamine into an organic solvent acetone, stirring and dissolving, to obtain component B;

[0065] S5: Add component B to component A, stir and disperse at high speed under low temperature of 10°C, and use immediately to obtain the anti-corrosion coating.

[0066] Example 2

[0067] A method for preparing an anti-corrosion coating for oil well tubulars comprises the following steps:

[0068] S1: Preparation of modified graphene:

[0069] S101: Add 3,5-diaminopyrazole and salicylaldehyde to anhydrous methanol, stir to dissolve, then drop 1M NaHCO3 solution, stir evenly, react at 60°C with stirring for 12h, cool to 15°C, filter, and recrystallize with anhydrous ethanol. Centrifuge and vacuum dry to obtain salicylaldehyde condensed with 3,5-diaminopyrazole Schif base complex; wherein the amount ratio of 3,5-diaminopyrazole, salicylaldehyde, anhydrous methanol, 1M NaHCO3 solution, and anhydrous ethanol is 10mmol:10mmol:30mL:3mL:15mL;

[0070] S102: adding nano-graphene oxide to a 70 wt % ethanol aqueous solution, stirring and dispersing, adding 3-isocyanate propyl triethoxysilane, stirring and reacting at 35° C. for 2 h, to obtain an isocyanate graphene suspension;

[0071] S103: adding 1H,1H-heptafluorobutylamine and salicylaldehyde 3,5-diaminopyrazole Schif base complex to the obtained isocyanate graphene suspension, stirring at 50° C. for 5 h, filtering, washing, and drying to obtain a modified intermediate;

[0072] S104: Add propylene oxide to anhydrous acetone, stir evenly, then add the obtained modified intermediate, mix evenly, then drop dibutyltin dilaurate, first stir and react at 55° C. for 5 h, then stir and react at 80° C. for 3 h, to obtain modified graphene;

[0073] In S102-S104, the mass ratio of nano-graphene oxide, 70wt% ethanol aqueous solution, 3-isocyanatepropyltriethoxysilane, 1H,1H-heptafluorobutylamine, salicylaldehyde 3,5-diaminopyrazole Schif base complex, glycidol, anhydrous acetone, and dibutyltin dilaurate is 1:15:0.5:0.15:0.2:0.2:3:0.03;

[0074] S2: Prepare the following materials in parts by mass: 50 parts of phenolic epoxy resin, 15 parts of modified graphene, 5 parts of fatty amine curing agent triethylenetetramine, 10 parts of active diluent 1,4-butanediol diglycidyl ether, and 10 parts of organic solvent acetone;

[0075] S3: After the phenolic epoxy resin and the modified graphene are evenly mixed, the active diluent 1,4-butanediol diglycidyl ether is added, and the mixture is evenly stirred to obtain component A;

[0076] S4: adding aliphatic amine curing agent triethylenetetramine into organic solvent acetone, stirring and dissolving, to obtain component B;

[0077] S5: Add component B to component A, stir and disperse at high speed under low temperature of 20°C, and use immediately to obtain the anti-corrosion coating.

[0078] In Comparative Example 1, nano-graphene oxide is used to replace the modified graphene in Example 1, and the other preparation processes are consistent with Example 1.

[0079] In Comparative Example 2, no salicylaldehyde condensation 3,5-diaminopyrazole Schif base complex is added during the preparation of modified graphene, and the other preparation processes are consistent with Example 1.

[0080] In Comparative Example 3, 1H,1H-heptafluorobutylamine was not added during the preparation of the modified graphene, and the other preparation processes were consistent with those of Example 1.

[0081] In Comparative Example 4, no glycidol was added during the preparation of the modified graphene, and the other preparation processes were consistent with those of Example 1.

[0082] In Comparative Example 5, 3,5-diaminopyrazole is used to replace the salicylaldehyde condensation 3,5-diaminopyrazole Schif base complex in Example 1, and the other preparation processes are consistent with Example 1.

[0083] The adhesion of the anticorrosive coatings prepared in Examples 1-2 and Comparative Examples 1-5 was measured according to the pull-off method in GB / T 5210-2006;

[0084] The acid resistance of the anticorrosive coatings prepared in Examples 1-2 and Comparative Examples 1-5 was measured according to GB / T 9274-1988; the acidic conditions were 28% HCl + 0.01% HCHO + 0.02% CH3COOH, the test temperature was 25°C, and the test days were 60 days.

[0085] The crude oil resistance of the anticorrosive coatings prepared in Examples 1-2 and Comparative Examples 1-5 was measured according to GB / T 9274-1988, with the test temperature being 80° C. and the test days being 90 days;

[0086] According to "Antibacterial Coatings" HG-T 3950-2007, the antibacterial properties of the anticorrosive coatings prepared in Examples 1-2 and Comparative Examples 1-5 were measured, and the test bacteria were sulfate-reducing bacteria. The broth medium (NB) formula of sulfate-reducing bacteria was: 5.0 g beef extract, 10.0 g peptone, 2.5 g sodium chloride, 5.0 g sodium sulfate, 1000 mL distilled water, pH = 7.0, and the culture medium was broth medium (NB) / physiological saline solution, and the culture medium concentration was 1 / 100.

[0087] The test results are shown in the following table:

[0088] Adhesion / MPa Acid resistance Crude oil resistance Antibacterial rate of sulfate-reducing bacteria / % Example 1 26.8 Coating intact Coating intact 99.4 Example 2 28.5 Coating intact Coating intact 99.8 Comparative Example 1 20.7 Obvious bubbling Foaming 78.6 Comparative Example 2 24.8 Foaming Foaming 78.8 Comparative Example 3 25.3 Slightly foamy Slightly foamy 99.5 Comparative Example 4 23.4 Slightly foamy Slightly foamy 99.4 Comparative Example 5 26.0 Coating intact Coating intact 90.7

[0089] It can be seen from the above table that the anti-corrosion coating prepared in Example 1-2 has good adhesion and corrosion resistance, and also exhibits excellent sulfate-reducing bacteria inhibition performance. It is applied to oil well pipes and can serve for a long time in high humidity, high pressure, high salt or high acid corrosive gas environments, blocking the contact between corrosive media and metal oil well pipes, and can operate for a long time in oil and gas fields containing high concentrations of H2S.

[0090] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention (including the claims) is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0091] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An anti-corrosion coating for oil well tubular goods, characterized in that: The invention comprises the following raw materials in parts by weight: 40-50 parts of phenolic epoxy resin, 10-15 parts of modified graphene, 1-5 parts of fatty amine curing agent, 5-10 parts of active diluent, and 5-10 parts of organic solvent; The preparation method of the modified graphene comprises the following steps: A1: Add 3,5-diaminopyrazole and salicylaldehyde to anhydrous methanol, stir to dissolve, then drop NaHCO3 solution, stir evenly, react at 40-60℃ for 6-12h, cool to 10-15℃, filter, recrystallize with anhydrous ethanol, centrifuge, and vacuum dry to obtain salicylaldehyde condensed with 3,5-diaminopyrazole Schif base complex; A2: Add nano-graphene oxide to an ethanol aqueous solution, stir and disperse, then add an isocyanate silane coupling agent, stir and react at 25-35°C for 1-2h to obtain an isocyanate graphene suspension; A3: Add 1H,1H-heptafluorobutylamine and salicylaldehyde 3,5-diaminopyrazole Schif base complex to the obtained isocyanate graphene suspension, stir and react at 30-50°C for 3-5h, filter, wash and dry to obtain a modified intermediate; A4: Add propylene oxide to anhydrous acetone, stir evenly, then add the obtained modified intermediate, mix evenly, then drop dibutyltin dilaurate, first stir and react at 50-55°C for 3-5h, then stir and react at 60-80°C for 2-3h to obtain modified graphene.

2. The anti-corrosion coating for oil well tubular goods according to claim 1, characterized in that: The dosage ratio of the 3,5-diaminopyrazole, salicylaldehyde, anhydrous methanol, NaHCO3 solution and anhydrous ethanol is 10mmol:10mmol:30mL:(2-3)mL:15mL.

3. The anti-corrosion coating for oil well tubular goods according to claim 1, characterized in that: The concentration of the NaHCO3 solution is 0.5-1M.

4. The anti-corrosion coating for oil well tubular goods according to claim 1, characterized in that: The concentration of the ethanol aqueous solution is 50-70wt%.

5. The anti-corrosion coating for oil well tubular goods according to claim 1, characterized in that: The isocyanate silane coupling agent is at least selected from 3-isocyanate propyl trimethoxy silane, 3-isocyanate propyl triethoxy silane, 3-isocyanate propyl methyl dimethoxy silane or 3-isocyanate propyl methyl diethoxy silane.

6. The anti-corrosion coating for oil well tubular goods according to claim 1, characterized in that: The mass ratio of the nano-graphene oxide, ethanol aqueous solution, isocyanate silane coupling agent, 1H,1H-heptafluorobutylamine, salicylaldehyde 3,5-diaminopyrazole Schif base complex, glycidol, anhydrous acetone, and dibutyltin dilaurate is 1:(10-15):(0.3-0.5):(0.05-0.15):(0.1-0.2):(0.1-0.2):(2-3):(0.01-0.03).

7. The anti-corrosion coating for oil well tubular goods according to claim 1, characterized in that: The fatty amine curing agent is at least one selected from hexamethylenediamine, diethylenetriamine and triethylenetetramine.

8. The anti-corrosion coating for oil well tubular goods according to claim 1, characterized in that: The active diluent is at least one selected from ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, and 1,6-hexanediol diglycidyl ether.

9. The anti-corrosion coating for oil well tubular goods according to claim 1, characterized in that: The organic solvent is at least one selected from dimethylformamide, acetone and cyclohexanone.

10. A method for preparing an anticorrosive coating for oil well tubular goods according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1: After the phenolic epoxy resin and the modified graphene are evenly mixed, the active diluent is added, and the mixture is evenly stirred to obtain component A; S2: Add the fatty amine curing agent into the organic solvent, stir and dissolve, and obtain component B; S3: Add component B to component A, stir and disperse at high speed under low temperature conditions of 10-20°C, and use immediately to obtain the anti-corrosion coating.