A high sulfur resistance tungsten alloy electroplating anti-corrosion process

Abstract

This application relates to the field of electroplating technology and specifically discloses a highly sulfur-resistant tungsten alloy electroplating corrosion protection process, comprising the following steps: adding nano-alumina to an ethanol solution, then adding a silane coupling agent, and ultrasonically treating the solution to produce a sol; under the protection of an inert gas, ultrasonically atomizing the solution to form an aerosol, methane, and a nano-silicon dioxide-coated nickel-tungsten alloy coating, subjecting the resulting product to a carbothermal reduction reaction; and cooling the product to produce a highly sulfur-resistant tungsten alloy electroplating layer. In this application, nano-silicon dioxide is synthesized in situ on the surface of the nickel-tungsten alloy, and then nano-alumina is introduced during the carbothermal reduction process to enhance the interfacial bonding between the silicon carbide and the nickel-tungsten alloy coating.

Description

Technical Field

[0001] The present application relates to the field of electroplating technology, and more specifically, to a high-sulfur-resistant tungsten alloy electroplating anti-corrosion process. Background Art

[0002] In recent years, due to increasingly demanding conditions for oil and gas field development, corrosion problems have become more serious in oilfield equipment, especially acidic corrosion caused by H2S and CO2. Many oil and gas pipelines, due to the presence of H2S, CO2, and formation water, are prone to perforation, hydrogen-induced cracking, sulfide stress corrosion cracking, and other destructive behaviors. To ensure safe and efficient production in oil and gas fields, methods such as adding corrosion inhibitors, using corrosion-resistant alloy steels, electrochemical protection, and coating protection are commonly used to improve the corrosion resistance of pipelines. Coating protection is a relatively preferred option. Tungsten alloy coatings offer excellent corrosion resistance, wear resistance, and high hardness, and can replace traditional chromium plating. The Ni-W alloy coating formed by electroplating has a nanocrystalline structure and is free of microcracks. This fine structure provides excellent stability. At the same time, it has a high hardness and can effectively resist external friction and impact.

[0003] Patent application document with publication number CN117187898A discloses a nano-silicon carbide reinforced nickel-tungsten alloy coating and preparation process. The application first optimizes the composition of the electroplating solution and adds rare earth elements neodymium trichloride and cerium sulfate to prepare the electroplating solution. Then, electroplating is performed with a 304 steel substrate as the cathode and a nickel plate as the anode to obtain a nano-nickel-tungsten alloy coating. Then, ethyl orthosilicate is added by liquid phase deposition to in-situ synthesize a nano-SiO2-coated nickel-tungsten alloy coating. Finally, methane is used as the carbon source and a carbon thermal reduction method is used to prepare a nano-silicon carbide reinforced nickel-tungsten alloy coating. However, the thermal expansion coefficient of SiO2 and nickel-tungsten alloy differs significantly (SiO2 is about 0.5×10 -6 / ℃, Ni-W alloy is about 13×10 -6 / ℃), thermal stress is easily generated at the interface after high temperature treatment, resulting in insufficient interface bonding strength between SiC and nickel-tungsten alloy. After long-term service, it is easy to crack at the interface and the corrosion resistance is reduced. Summary of the Invention

[0004] In order to improve the interface bonding strength between SiC and nickel-tungsten alloy, and thus improve the corrosion resistance of the coating, the present application provides a high sulfur-resistant tungsten alloy electroplating anti-corrosion process.

[0005] This application provides a high sulfur resistance tungsten alloy electroplating anti-corrosion process, which adopts the following technical solutions:

[0006] A high sulfur resistance tungsten alloy electroplating anti-corrosion process comprises the following steps:

[0007] (1) Electroplating the workpiece in a nickel-tungsten alloy plating solution to obtain a nickel-tungsten alloy coating;

[0008] (2) Using a liquid phase deposition method, a silicon source is used to in situ synthesize nano-silicon dioxide on the surface of the nickel-tungsten alloy coating to obtain a nano-silicon dioxide-coated nickel-tungsten alloy coating;

[0009] (3) Adding nano-alumina to an ethanol solution, then adding a silane coupling agent, and ultrasonicating to obtain a sol;

[0010] (4) Under the protection of an inert gas, the aerosol formed by ultrasonic atomization of the sol, methane and the nano-silicon dioxide coated nickel-tungsten alloy coating are subjected to a carbon thermal reduction reaction to obtain a product, and the product is cooled to obtain a high sulfur-resistant tungsten alloy electroplating layer.

[0011] By adopting the above-mentioned technical solution, the present invention, after in-situ synthesis of nano-silicon dioxide on the surface of nickel-tungsten alloy, introduces nano-aluminum oxide during the carbothermal reduction process to improve the interfacial bonding between silicon carbide and nickel-tungsten alloy coatings. Specifically, the aluminum oxide undergoes a trace reaction with the silicon dioxide and nickel-tungsten alloy, enhancing the chemical bonding at the interface. Furthermore, its thermal expansion coefficient lies between that of SiC and nickel-tungsten alloy, effectively alleviating thermal stress mismatch during cooling and reducing the risk of interfacial cracking. Furthermore, the nano-aluminum oxide acts as a heterogeneous nucleation site, promoting SiC grain refinement and further enhancing bonding strength through a mechanical interlocking effect.

[0012] At the same time, Al2O3 has excellent chemical stability and can react with sulfur ions (S 2- ) react to form a stable Al2S3 compound, which covers the surface of the coating and prevents sulfur from penetrating into the substrate; at the same time, when corrosion occurs on the surface of the coating, Al2O3 can induce the formation of a dense oxidation-sulfurization composite passivation film (such as an Al2O3-Al2S3 mixed layer). This film has high resistance and low permeability, and can effectively isolate the corrosive medium; in addition, after Al2O3 strengthens the interface, the strong interfacial bonding force can avoid the formation of micro-battery corrosion channels between the reinforcing phase (such as SiC) and the substrate, which can block the diffusion path of the corrosive medium and improve the comprehensive performance of the coating.

[0013] Preferably, in step (4), the aerosol and methane are simultaneously introduced into the nano-silica-coated nickel-tungsten alloy layer, the temperature during the carbon thermal reduction reaction is 1200-1400°C, the heating rate is 5-10°C / min, the methane flow rate is 50-200sccm, the aerosol spray rate and the methane flow rate ratio is (0.1-0.5):1; and the total pressure of the system is 10-100Pa.

[0014] By adopting the above technical solution, aerosol and methane are simultaneously introduced into the nano-silica-coated nickel-tungsten alloy layer. Al2O3 can participate in the interface construction in the early stage of SiC nucleation to form a SiC-Al2O3-Ni-W composite interface transition layer, thereby improving the interface bonding strength between silicon carbide and the nickel-tungsten alloy coating. In the late stage of SiC nucleation, Al2O3 needs to diffuse to the interface between SiC and the alloy at high temperature, fill defects through the dissolution-precipitation mechanism, or react with SiC and the alloy to form a transition phase, thereby improving the interface bonding strength.

[0015] Too low a temperature during carbothermal reduction will result in low methane cracking efficiency, slow carbothermal reduction reaction rate, insufficient SiC nucleation and growth, and difficulty in interfacial reaction between Al2O3 and the alloy; while too high a temperature will lead to excessive decomposition of methane, producing a large amount of amorphous carbon encapsulating Al2O3 nanoparticles, hindering the contact between the nanoparticles and the alloy matrix. At the same time, high temperature may aggravate the agglomeration of Al2O3.

[0016] Rapid heating will lead to local overheating, causing methane to crack prematurely in the low-temperature section to generate carbon black, which will be deposited on the surface of Al2O3 to form a "carbon shell"; slow heating can allow Al2O3 to be evenly adsorbed on the alloy surface first, and then synergistically participate in the reaction with methane.

[0017] Too high a methane flow rate will lead to excessive carbon source per unit time, rapid nucleation and growth of SiC, wrapping the insufficiently dispersed Al2O3 particles to form "SiC-Al2O3" mixed agglomerates, and the interface bonding strength will decrease; too low a flow rate will lead to insufficient carbon source, small amount of SiC generated, and Al2O3 cannot be effectively embedded in the interface between SiC and alloy, thus losing its transition layer function.

[0018] As a carbon source, the flow rate of methane must balance carbon deposition and interfacial reaction requirements. Too high a flow rate can easily produce excess carbon, impacting bonding strength, while too low a flow rate can result in insufficient carbon source. The amount of modified Al2O3 nanoparticles carried by the aerosol must be matched to the concentration of active species generated by methane decomposition and the carrier gas flow rate to ensure uniform particle dispersion and effective deposition. Furthermore, this ratio must be set to ensure that the nanoparticle deposition rate matches the growth rate of the Ni-W alloy coating, promoting the formation of a transition layer between the carbon species, the particles, and the alloy, enhancing interfacial bonding, and preventing the formation of brittle phases, ultimately achieving overall optimization of coating performance.

[0019] High pressure will promote the thermal decomposition reaction of methane, accelerate carbon deposition, and lead to the deterioration of Al2O3 dispersion; low pressure environment can slow down the carbon deposition rate and provide time for the interface diffusion of Al2O3.

[0020] Preferably, in step (3), the amount of the silane coupling agent added is 0.5%-1.5% of the mass of the nano-alumina; the particle size of the nano-alumina is 50-100 nm, and the mass concentration of the sol is 5%-15%.

[0021] By adopting the above technical solution, when the amount of silane coupling agent is insufficient, the hydroxyl groups on the surface of nano-alumina cannot be fully coated, resulting in particle agglomeration and weak interface bonding with the matrix; when the amount is appropriate, the coupling agent molecules form a monolayer on the surface of alumina, improving dispersibility and enhancing compatibility with the organic phase through covalent bonds; excessive amount will cause the coupling agent to self-aggregate, forming agglomerates and increasing the viscosity of the sol, which in turn destroys the uniformity of the interface.

[0022] The smaller the nano-alumina particle size, the higher the specific surface area and surface hydroxyl density, and more coupling agents are required to achieve complete coating. After modification, the dispersion is excellent but it is easy to agglomerate due to excessive surface energy; the larger the particle size, the smaller the specific surface area, and the amount of coupling agent can be reduced, but the interfacial contact area is small and the uniformity of the modified layer is reduced; a wide particle size distribution will lead to large differences in the number of hydroxyl groups, uneven adsorption of the coupling agent, and aggravated the inconsistency of particle dispersion in the sol.

[0023] When the sol mass concentration is too low, the nano-alumina particles are sparsely dispersed, the collision efficiency with the coupling agent is low, the modification is insufficient and the sol stability is poor; when the concentration is moderate, the particle spacing is appropriate, the ultrasonic dispersion is uniform, the coupling agent can be fully adsorbed, and the sol viscosity and fluidity are balanced; when the concentration is too high, the particles collide frequently, it is difficult to completely disperse them by ultrasound, clusters are easily formed, the sol viscosity is too high or even gels, resulting in uneven modification.

[0024] Preferably, in step (4), the product is further annealed before cooling, specifically, annealing the product in a mixture of hydrogen and argon at 400-600° C. for 0.5-2 h.

[0025] By adopting the above technical solution, annealing treatment promotes atomic diffusion at the interface of Al2O3 and Ni-W alloy, forming a transition layer, further enhancing the bonding strength and reducing the risk of cracking; at the same time, it eliminates the lattice distortion generated during the reaction process, refines the SiC / Al2O3 composite particles, and improves the uniformity of the coating.

[0026] Preferably, in step (1), the process conditions during electroplating are: temperature of 65-75°C, pH value of 8.0-9.5, current density of 4-8A / dm 2 , the electroplating time is 10-30min.

[0027] By adopting the above technical solution, increasing the temperature can accelerate the diffusion of metal ions, increase the deposition rate, improve the uniformity of the coating and refine the grains, but too high a temperature will intensify hydrogen evolution, cause the decomposition of additives, make the coating rough or cause hydrogen embrittlement.

[0028] The pH value affects the complexation state of metal ions and the hydrogen evolution potential. Under acidic conditions, ion reduction is fast but the competition for hydrogen evolution is strong. Under alkaline conditions, precipitation is easily generated. The appropriate pH value can regulate the composition of the alloy coating to avoid increased porosity or excessive internal stress.

[0029] The current density determines the deposition rate and the cathode polarization intensity. At low current density, the grains are coarse, and at medium current density, a dense and fine-grained coating can be formed. High current density can easily lead to "burning" or hydrogen embrittlement of the coating, and uneven thickness is easily caused by the shape of the workpiece.

[0030] The electroplating time is positively correlated with the thickness of the coating. If the time is too short, the coating may be too thin and the coverage may be incomplete. If the time is too long, the internal stress may increase, the grains may coarsen, and even the performance may deteriorate due to the imbalance of the plating solution composition. The time must be precisely controlled according to the needs.

[0031] Therefore, by precisely controlling the process parameters during electroplating, the coating thickness, density, and corrosion resistance can be optimized.

[0032] Preferably, in step (1), the formula of the nickel-tungsten alloy plating solution is: 25-35 g / L nickel sulfate, 40-50 g / L sodium tungstate, 40-50 g / L complexing agent, 0.1-0.2 g / L sodium dodecylbenzenesulfonate, 1-2.5 g / L sodium saccharin and 15-20 g / L sodium sulfate.

[0033] By adopting the above technical solution, the nickel-tungsten alloy coating formed by this formula has both high hardness and excellent sulfur corrosion resistance.

[0034] Preferably, the formula of the nickel-tungsten alloy plating solution further includes 0.8-1.2 g / L of a rare earth-graphene composite. The preparation method of the rare earth-graphene composite is as follows: adding graphene oxide, a rare earth salt and polyethylene glycol to a solvent, adjusting the pH to 5-7 under an inert atmosphere, heating to 70-90° C. for reaction for 3-6 hours, and then adding a reducing agent to obtain the rare earth-graphene composite;

[0035] The molecular weight of the polyethylene glycol is 1000-2000;

[0036] The molar ratio of the rare earth to polyethylene glycol is 1:(1-3);

[0037] The mass ratio of the graphene to the polyethylene glycol is 1:(0.5-2).

[0038] By adopting the above technical solution, rare earth-graphene is added to the plating solution. The rare earth acts as a heterogeneous nucleus and its core and the spatial steric hindrance effect of graphene jointly refine the grains and improve the density of the coating; the reinforcing phase effect of rare earth and graphene synergistically improves the hardness, wear resistance and toughness of the coating, and enhances the corrosion resistance through the dual mechanism of forming a composite passivation film and isolating the corrosive medium; the electrocatalytic activity of rare earth and the high conductivity of graphene optimize the electrodeposition process, increase the deposition rate and current efficiency, and at the same time stabilize the composition of the plating solution and improve the dispersion ability.

[0039] Using polyethylene glycol as a bridge molecule, the oxygen atom in its ether bond acts as an electron donor, forming a coordination bond with the rare earth ion. Simultaneously, its hydroxyl groups can hydrogen bond or esterify with functional groups on the graphene surface (such as hydroxyl and carboxyl groups). This triple action of coordination, hydrogen bonding, and chemical bonding achieves efficient bonding between rare earth and graphene.

[0040] Preferably, the rare earth salt is one of lanthanum nitrate, cerium sulfate, lanthanum chloride, cerium nitrate, praseodymium acetate, and neodymium fluoride, and more preferably cerium sulfate.

[0041] By adopting the above technical solution, the nucleation effect of rare earth ions is utilized to promote the refinement of nickel-tungsten grains, thereby improving the microhardness and surface smoothness of the coating. The nickel-tungsten co-deposition is accelerated by reducing the metal ion reduction overpotential, while the hydrogen evolution side reaction is suppressed to reduce porosity and hydrogen embrittlement. Its oxidizing components form a dense passivation film on the surface of the coating, which synergizes with the physical barrier effect of graphene to significantly enhance corrosion resistance. Rare earths can also improve the dispersibility of graphene in the plating solution, avoid agglomeration and enhance the interfacial bonding between graphene and the nickel-tungsten matrix. The uniformity of tungsten deposition is optimized by stabilizing the composition of the plating solution, ultimately achieving an improvement in the overall performance of the coating.

[0042] Cerium sulfate is oxidizing and can form Ce in the plating solution. 3+ / Ce 4+ The redox couple inhibits the hydrogen evolution side reaction and simultaneously forms a cerium oxide passivation film on the coating surface, which not only improves the corrosion resistance of the coating and isolates the corrosive medium (such as sulfur-containing environment), but also reduces the risk of hydrogen embrittlement (inhibits cathode hydrogen evolution) and enhances the adhesion of the coating.

[0043] Preferably, the formula of the nickel-tungsten alloy plating solution further includes 2-4 g / L of cobalt sulfate and 3-6 g / L of sodium molybdate.

[0044] By adopting the above technical solutions, cobalt and molybdenum can increase the electrode potential of the alloy, making the coating more difficult to oxidize in a sulfur-containing environment; tungsten forms a hard carbide / boride skeleton to hinder the diffusion and penetration of sulfides; molybdenum easily forms a molybdenum sulfide passivation film in acidic or neutral sulfur-containing media. This film has good chemical stability and can isolate the contact between sulfur ions and the substrate.

[0045] Preferably, the complexing agent is a mixture of sodium citrate, lactic acid and triethylenetriamine in a mass ratio of (4-6): (1-3): (2-5).

[0046] By adopting the above technical solution, sodium citrate forms a stable complex with metal ions through its multi-carboxyl structure, providing basic complexing capacity for the plating solution and controlling the release rate of metal ions. Lactic acid, as a hydroxycarboxylic acid, can not only coordinate with metal ions to enhance the stability of the complex system, but also maintain the acid-base balance of the system by adjusting the pH value of the plating solution, reducing the hydrolysis and precipitation of metal ions. Triethylenetriamine, as a polyamine compound, forms strong coordination bonds with metal ions with its multiple nitrogen atoms, further improving the stability constant of the complex. At the same time, the amino groups in its molecular structure can form a complex complex network through hydrogen bonding with the carboxyl or hydroxyl groups of sodium citrate and lactic acid, optimizing the coordination environment of the metal ions. The synergistic effect of the three can not only accurately control the free concentration of metal ions in the plating solution, making the deposition process uniform and controllable, but also inhibit the decomposition of the plating solution through the buffering effect of the multi-component complex system, reducing the incidence of side reactions, and ultimately achieving a stable deposition rate, improved density and uniformity of the coating, and extended plating solution service life.

[0047] In summary, this application has the following beneficial effects:

[0048] 1. After in-situ synthesis of nano-silicon dioxide on the surface of nickel-tungsten alloy, the present invention adds nano-aluminum oxide during carbothermal reduction using methane as a carbon source, thereby improving the interfacial bonding strength between silicon carbide and nickel-tungsten alloy coating.

[0049] 2. In this application, aerosol and methane are simultaneously introduced into the nano-silica-coated nickel-tungsten alloy layer. Al2O3 can participate in the interface construction in the early stage of SiC nucleation to form an interface transition layer, thereby improving the interface bonding strength between silicon carbide and the nickel-tungsten alloy coating; in the late stage of SiC nucleation, it fills defects through the dissolution-precipitation mechanism or reacts with SiC and alloy to form a transition phase, thereby improving the interface bonding strength.

[0050] 3. In this application, the product obtained after the carbon thermal reduction reaction is annealed, which can promote the atomic diffusion of Al2O3 and Ni-W alloy interface, form a transition layer, further enhance the bonding strength, reduce the risk of cracking, and eliminate the lattice distortion generated during the reaction process, refine the SiC / Al2O3 composite particles, and improve the uniformity of the coating.

[0051] 4. In the present application, rare earth and graphene are combined with polyethylene glycol through "coordination-hydrogen bond-chemical bond" to obtain a rare earth-graphene composite, and the composite is added to the plating solution. The rare earth can not only form a dense passivation film on the surface of the coating, but also significantly enhance the corrosion resistance by synergizing the physical barrier effect of graphene. It can also improve the dispersion of graphene in the plating solution, avoid agglomeration and enhance the interfacial bonding between graphene and the nickel-tungsten matrix. Moreover, the uniformity of tungsten deposition is optimized by stabilizing the composition of the plating solution, thereby ultimately improving the overall performance of the coating. DETAILED DESCRIPTION

[0052] The present application is further described in detail below with reference to the embodiments.

[0053] Unless otherwise specified, the raw materials used in the preparation examples, embodiments and comparative examples of this application are all commercially available.

[0054] Preparation Example 1-4 Rare Earth-Graphene Composite

[0055] Preparation Example 1

[0056] This preparation example discloses a method for preparing a rare earth-graphene composite, which specifically includes the following steps:

[0057] 10 g of graphene oxide powder was added to 1 L of deionized water, placed in an ultrasonic cleaner, and ultrasonicated at a frequency of 40 kHz for 45 min to fully disperse the graphene oxide and form a uniform suspension;

[0058] 10 g of cerium nitrate was added to the above suspension and stirred at 300 r / min using a magnetic stirrer for 20 min to completely dissolve the cerium nitrate. 0.5 g of polyethylene glycol with a molecular weight of 4000 was then added and stirred for 15 min to form a stable mixture.

[0059] The mixed solution was transferred to a three-necked flask, and a condenser, thermometer, and inert gas inlet device were installed. Nitrogen was passed into the three-necked flask at a gas flow rate of 50 mL / min for 15 min to remove air from the system. 0.1 mol / L hydrochloric acid solution was added dropwise to adjust the pH of the solution to 5. The three-necked flask was placed in a constant temperature water bath, heated to 70°C, and magnetically stirred at 300 r / min for 6 h. After the reaction was completed, heating was stopped, the three-necked flask was removed from the constant temperature water bath, and naturally cooled to room temperature.

[0060] 10 g of ascorbic acid was added to the reaction system, and the mixture was stirred at 300 r / min for 1.5 h to obtain the product; the product was transferred to a centrifuge tube, centrifuged at 600 r / min for 10 min, and the solid product was separated. The solid product was washed three times with deionized water and ethanol, respectively, and centrifuged at 600 r / min for 5 min after each washing; the washed product was placed in a vacuum drying oven and dried at 60°C for 12 h to obtain a rare earth-graphene composite.

[0061] Preparation Example 2

[0062] This preparation example discloses a method for preparing a rare earth-graphene composite, which specifically includes the following steps:

[0063] 10 g of graphene oxide powder was added to 1 L of deionized water, placed in an ultrasonic cleaner, and ultrasonicated at a frequency of 40 kHz for 45 min to fully disperse the graphene oxide and form a uniform suspension;

[0064] 15 g of cerium nitrate was added to the suspension and stirred at 300 r / min using a magnetic stirrer for 20 min to completely dissolve the cerium nitrate. 1.5 g of polyethylene glycol (molecular weight 4000) was then added and stirred for 15 min to form a stable mixture.

[0065] The mixed solution was transferred to a three-necked flask, and a condenser, thermometer, and inert gas inlet device were installed. Nitrogen was passed into the three-necked flask at a gas flow rate of 50 mL / min for 15 min to remove air from the system. 0.1 mol / L sodium hydroxide solution was added dropwise to adjust the pH of the solution to 6. The three-necked flask was placed in a constant temperature water bath, heated to 80°C, and magnetically stirred at 300 r / min for 4 h. After the reaction was completed, heating was stopped, the three-necked flask was removed from the constant temperature water bath, and naturally cooled to room temperature.

[0066] 10 g of ascorbic acid was added to the reaction system, and the mixture was stirred at 300 r / min for 1.5 h to obtain the product; the product was transferred to a centrifuge tube, centrifuged at 600 r / min for 10 min, and the solid product was separated. The solid product was washed three times with deionized water and ethanol, respectively, and centrifuged at 600 r / min for 5 min after each washing; the washed product was placed in a vacuum drying oven and dried at 60°C for 12 h to obtain a rare earth-graphene composite.

[0067] Preparation Example 3

[0068] This preparation example discloses a method for preparing a rare earth-graphene composite, which specifically includes the following steps:

[0069] 10 g of graphene oxide powder was added to 1 L of deionized water, placed in an ultrasonic cleaner, and ultrasonicated at a frequency of 40 kHz for 45 min to fully disperse the graphene oxide and form a uniform suspension;

[0070] 20 g of cerium nitrate was added to the suspension and stirred at 300 r / min using a magnetic stirrer for 20 min to completely dissolve the cerium nitrate. 2 g of polyethylene glycol (molecular weight 4000) was then added and stirred for 15 min to form a stable mixture.

[0071] The mixed solution was transferred to a three-necked flask, and a condenser, thermometer, and inert gas inlet device were installed. Nitrogen was passed into the three-necked flask at a gas flow rate of 50 mL / min for 15 min to remove air from the system. 0.1 mol / L sodium hydroxide solution was added dropwise to adjust the pH of the solution to 7. The three-necked flask was placed in a constant temperature water bath, heated to 90°C, and magnetically stirred at 300 r / min for 3 h. After the reaction was completed, heating was stopped, the three-necked flask was removed from the constant temperature water bath, and naturally cooled to room temperature.

[0072] 10 g of ascorbic acid was added to the reaction system, and the mixture was stirred at 300 r / min for 1.5 h to obtain the product; the product was transferred to a centrifuge tube, centrifuged at 600 r / min for 10 min, and the solid product was separated. The solid product was washed three times with deionized water and ethanol, respectively, and centrifuged at 600 r / min for 5 min after each washing; the washed product was placed in a vacuum drying oven and dried at 60°C for 12 h to obtain a rare earth-graphene composite.

[0073] Preparation Example 4

[0074] This preparation example discloses a method for preparing a rare earth-graphene composite, which specifically includes the following steps:

[0075] 10 g of graphene oxide powder was added to 1 L of deionized water, placed in an ultrasonic cleaner, and ultrasonicated at a frequency of 40 kHz for 45 min to fully disperse the graphene oxide and form a uniform suspension;

[0076] 15 g of cerium nitrate was added to the suspension and stirred at 300 r / min using a magnetic stirrer for 20 min to completely dissolve the cerium nitrate. 1.5 g of polyethylene glycol (molecular weight: 6000) was then added and stirred for 15 min to form a stable mixture.

[0077] The mixed solution was transferred to a three-necked flask, and a condenser, thermometer, and inert gas inlet device were installed. Nitrogen was passed into the three-necked flask at a gas flow rate of 50 mL / min for 15 min to remove air from the system. 0.1 mol / L sodium hydroxide solution was added dropwise to adjust the pH of the solution to 6. The three-necked flask was placed in a constant temperature water bath, heated to 80°C, and magnetically stirred at 300 r / min for 4 h. After the reaction was completed, heating was stopped, the three-necked flask was removed from the constant temperature water bath, and naturally cooled to room temperature.

[0078] 10 g of ascorbic acid was added to the reaction system, and the mixture was stirred at 300 r / min for 1.5 h to obtain the product; the product was transferred to a centrifuge tube, centrifuged at 600 r / min for 10 min, and the solid product was separated. The solid product was washed three times with deionized water and ethanol, respectively, and centrifuged at 600 r / min for 5 min after each washing; the washed product was placed in a vacuum drying oven and dried at 60°C for 12 h to obtain a rare earth-graphene composite.

[0079] Example 1

[0080] This embodiment provides a high sulfur-resistant tungsten alloy electroplating anti-corrosion process, including the following steps:

[0081] (1) Pretreatment: Fix a carbon steel specimen with a size of 50 mm × 25 mm × 1.8 mm on a rotating fixture and sandblast it. Adjust the compressed air pressure to 0.4 MPa, keep the sandblasting gun head 12 cm away from the pipe surface, and continue for 5 minutes. After sandblasting, blow the surface of the carbon steel specimen with compressed air to remove residual sand and dust, and then transfer the carbon steel specimen to an ultrasonic cleaner for cleaning. Prepare a degreasing solution in a degreasing tank. Add 50 g / L sodium hydroxide, 20 g / L sodium carbonate, 25 g / L trisodium phosphate and 2.0 g / L O-10 surfactant into deionized water, stir evenly and heat to 75 °C. Place the sandblasted carbon steel specimen in the degreasing tank and soak for 10 minutes. During this period, turn the carbon steel specimen every 2 minutes. After the end, take out the carbon steel specimen and rinse it with 60 °C running hot water for 3 minutes. Use a stainless steel plate as the anode and a carbon steel specimen as the cathode. Place them in a solution with the same composition as the chemical degreasing solution. Connect the rectifier and set the current density to 7 A / dm 2 , the temperature is maintained at 65 ° C, the treatment time is 2 minutes, and electrochemical degreasing is performed. After the degreasing is completed, the workpiece is rinsed with running cold water; 18wt% hydrochloric acid solution is prepared in the pickling tank, and the carbon steel test block is immersed in it. It is soaked at room temperature for 4 minutes. The carbon steel test block is taken out and the inner and outer walls of the workpiece are rinsed with running deionized water for 5 minutes;

[0082] (2) Pre-nickel plating: prepare a pre-plating solution in a pre-plating tank, add 90 g / L nickel sulfate, 55 g / L sodium citrate, and 28 g / L boric acid into deionized water, add 0.1 mol / L sodium hydroxide solution dropwise, adjust the pH to 9.0, raise the temperature to 55°C, hang the pretreated carbon steel test block in the pre-plating tank, use the nickel block as the anode, turn on the power supply, and set the current density to 2 A / dm 2 , pre-plating for 10 minutes, after the pre-plating is completed, rinse the surface of the carbon steel test block with deionized water;

[0083] (3) Electroplating of nickel-tungsten alloy layer: prepare the electroplating solution in the electroplating tank, add 25g / L nickel sulfate, 40g / L sodium tungstate, 40g / L chelating agent (16g / L sodium citrate, 4g / L lactic acid and 20g / L triethylenetriamine), 0.1g / L sodium dodecylbenzenesulfonate, 1g / L sodium saccharin and 15g / L sodium sulfate into deionized water, add 0.1mol / L sodium hydroxide solution dropwise, adjust the pH to 8, raise the temperature to 65℃, hang the carbon steel sample after pre-plating nickel layer in the pre-plating tank, use nickel block as anode, set auxiliary anode, turn on the mechanical stirrer and air stirring device, the stirring speed is 120r / min, and the air flow rate is 8m 3 / h, turn on the power and set the current density to 4A / dm 2 , the electroplating time is 60 min. After the electroplating is completed, the carbon steel test piece is washed with deionized water to obtain a nickel-tungsten alloy coating;

[0084] (4) 7.5 mL of 30 wt% ammonia water was mixed with 300 mL of isopropyl alcohol to form a mixed solution. The electroplated carbon steel specimen was immersed in the mixed solution and soaked in a water bath at 45 °C for 50 min. After soaking, 60 g / L of ethyl orthosilicate solution was added and stirred for 4 h using a magnetic stirrer to obtain a carbon steel specimen with a nano-silica coated nickel-tungsten alloy coating.

[0085] (5) 5 g of nano-alumina with an average particle size of 80 nm was dispersed in 109 mL of 75 wt% ethanol solution, and then 0.025 g of KH550 was added, and 1 mol / L of ammonia water was added dropwise to adjust the pH of the system to 9 to obtain a mixed solution. The mixed solution was placed in an ice-water bath and ultrasonically dispersed at a power of 300 W for 30 min to obtain a 5 wt% sol. A carbon steel specimen coated with nano-silica and nickel-tungsten alloy was placed in a tube furnace and introduced with 300 sccm of argon. The temperature was raised to 800 ° C at a rate of 5 ° C / min, and the air in the tube was removed. The temperature was continued to rise to 1200 ° C, and the gas flow rate was switched to a mixed gas of methane and argon with a volume ratio of 1:4 with a gas flow rate of 250 sccm. At the same time, an ultrasonic atomizer with a power of 300 W was used to convert the sol into an aerosol and introduced into the reaction chamber at a spray rate of 5 mL / min. The total pressure of the system was controlled to 10 Pa. The reaction was carried out for 4 h, and the mixture was cooled to room temperature to obtain a high sulfur-resistant tungsten alloy coating.

[0086] Example 2

[0087] This embodiment is basically the same as embodiment 1, except that, in step (5), 5 g of nano-alumina with an average particle size of 80 nm is dispersed in 51.6 mL of 75 wt% ethanol solution, 0.05 g of KH550 is added, and 1 mol / L of ammonia water is added dropwise to adjust the pH of the system to 9 to obtain a mixed solution, the mixed solution is placed in an ice water bath, and ultrasonically dispersed at a power of 300 W for 30 min to obtain a 10 wt% sol; a carbon steel test block coated with a nickel-tungsten alloy coating of nano-silica is placed in a tube The furnace was filled with 300 sccm argon and heated to 800°C at a rate of 8°C / min. The air in the tube was removed and the temperature was continued to rise to 1300°C. The gas flow rate was switched to a mixture of methane and argon with a volume ratio of 1:4 at 500 sccm. At the same time, an ultrasonic atomizer with a power of 300 W was used to convert the sol into an aerosol and introduced it into the reaction chamber at a spray rate of 30 mL / min. The total pressure of the system was controlled to 50 Pa. The reaction was carried out for 3 hours and the coating was cooled to room temperature to obtain a high sulfur-resistant tungsten alloy coating.

[0088] Example 3

[0089] This embodiment is basically the same as embodiment 1, except that, in step (5), 5 g of nano-alumina with an average particle size of 80 nm is dispersed in 32.4 mL of 75 wt% ethanol solution, 0.075 g of KH550 is added, and 1 mol / L of ammonia water is added dropwise to adjust the pH of the system to 9 to obtain a mixed solution, the mixed solution is placed in an ice water bath, and ultrasonically dispersed at a power of 300 W for 30 min to obtain a 15 wt% sol; a carbon steel test block coated with a nickel-tungsten alloy coating of nano-silica is placed in a tube furnace 300 sccm argon was introduced into the tube, and the temperature was raised to 800°C at a rate of 10°C / min. The air in the tube was removed and the temperature was continued to rise to 1400°C. The gas flow rate was switched to a mixed gas of methane and argon with a volume ratio of 1:4 at a rate of 1000 sccm. At the same time, an ultrasonic atomizer with a power of 300 W was used to convert the sol into an aerosol and introduced into the reaction chamber at a spray rate of 100 mL / min. The total pressure of the system was controlled to 100 Pa. The reaction was carried out for 2 hours and the tube was cooled to room temperature to obtain a high sulfur-resistant tungsten alloy coating.

[0090] Example 4

[0091] This embodiment is basically the same as embodiment 2, except that, in step (5), 5 g of nano-alumina with an average particle size of 80 nm is dispersed in 51.6 mL of 75 wt% ethanol solution, 0.05 g of KH550 is added, and 1 mol / L of ammonia water is added dropwise to adjust the pH of the system to 9 to obtain a mixed solution, the mixed solution is placed in an ice water bath, and ultrasonically dispersed at a power of 300 W for 30 min to obtain a 10 wt% sol; a carbon steel test block coated with a nano-silica nickel-tungsten alloy is placed in a tube furnace and 300 sccm of argon is introduced, and the mixture is heated at a speed of 8 ° C / min. The temperature was raised to 800°C at a high rate, the air in the tube was removed, and the temperature was continued to rise to 1300°C. The gas flow rate was switched to a mixed gas of methane and argon with a volume ratio of 1:4 at a flow rate of 500sccm. At the same time, an ultrasonic atomizer with a power of 300W was used to convert the sol into an aerosol and introduced into the reaction chamber at a spray rate of 30mL / min. The total pressure of the system was controlled to be 50Pa. The reaction was carried out for 3h to obtain the product. The product was annealed at 500°C for 1h in a mixed gas of hydrogen and argon with a volume ratio of 1:9 at a flow rate of 100sccm, and then cooled to room temperature to obtain a high sulfur-resistant tungsten alloy coating.

[0092] Example 5

[0093] This embodiment is basically the same as embodiment 4, except that, in step (3), nickel-tungsten alloy layer is electroplated: an electroplating solution is prepared in an electroplating tank, 30 g / L nickel sulfate, 45 g / L sodium tungstate, 45 g / L complexing agent (22.5 g / L sodium citrate, 9 g / L lactic acid and 13.5 g / L triethylenetriamine), 0.15 g / L sodium dodecylbenzenesulfonate, 1.5 g / L sodium saccharin and 17.5 g / L sodium sulfate are added to deionized water, 0.1 mol / L sodium hydroxide solution is added dropwise, the pH is adjusted to 9, the temperature is raised to 70°C, the carbon steel sample after pre-nickel plating is hung in the pre-plating tank, the nickel block is used as the anode, and an auxiliary anode is set, the mechanical stirrer and the air stirring device are turned on, the stirring speed is 120 r / min, and the air flow rate is 8 m 3 / h, turn on the power and set the current density to 6A / dm 2 The electroplating time was 45 min. After the electroplating was completed, the carbon steel test block was washed with deionized water to obtain a nickel-tungsten alloy coating.

[0094] Example 6

[0095] This embodiment is basically the same as embodiment 4, except that, in step (3), nickel-tungsten alloy layer is electroplated: an electroplating solution is prepared in an electroplating tank, 36 g / L nickel sulfate, 50 g / L sodium tungstate, 50 g / L complexing agent (30 g / L sodium citrate, 15 g / L lactic acid and 5 g / L triethylenetriamine), 0.2 g / L sodium dodecylbenzenesulfonate, 2.5 g / L sodium saccharin and 20 g / L sodium sulfate are added to deionized water, 0.1 mol / L sodium hydroxide solution is added dropwise, the pH is adjusted to 9.5, the temperature is raised to 75°C, the carbon steel sample after pre-nickel plating is hung in the pre-plating tank, the nickel block is used as the anode, and an auxiliary anode is set, the mechanical stirrer and the air stirring device are turned on, the stirring speed is 120 r / min, and the air flow rate is 8 m 3 / h, turn on the power and set the current density to 8A / dm 2 The electroplating time was 30 min. After the electroplating was completed, the carbon steel test block was washed with deionized water to obtain a nickel-tungsten alloy coating.

[0096] Example 7

[0097] This embodiment is basically the same as embodiment 4, except that, in step (3), the nickel-tungsten alloy layer is electroplated: an electroplating solution is prepared in an electroplating tank, 30 g / L nickel sulfate, 45 g / L sodium tungstate, 45 g / L complexing agent (22.5 g / L sodium citrate, 9 g / L lactic acid and 13.5 g / L triethylenetriamine), 0.8 g / L rare earth graphene complex, 0.15 g / L sodium dodecylbenzenesulfonate, 1.5 g / L sodium saccharin and 17.5 g / L sodium sulfate are added to deionized water, 0.1 mol / L sodium hydroxide solution is added dropwise, the pH is adjusted to 9, the temperature is raised to 70°C, the carbon steel sample after the nickel layer is pre-plated is hung in the pre-plating tank, the nickel block is used as the anode, and an auxiliary anode is set, the mechanical stirrer and the air stirring device are turned on, the stirring speed is 120 r / min, and the air flow rate is 8 m 3 / h, turn on the power and set the current density to 6A / dm 2 The electroplating time was 45 min. After the electroplating was completed, the carbon steel test block was washed with deionized water to obtain a nickel-tungsten alloy coating.

[0098] The rare earth-graphene composite is from Preparation Example 1.

[0099] Example 8

[0100] This embodiment is basically the same as embodiment 4, except that, in step (3), nickel-tungsten alloy layer is electroplated: an electroplating solution is prepared in an electroplating tank, 30 g / L nickel sulfate, 45 g / L sodium tungstate, 45 g / L complexing agent (22.5 g / L sodium citrate, 9 g / L lactic acid and 13.5 g / L triethylenetriamine), 0.4 g / L cerium nitrate, 0.4 g / L graphene, 0.15 g / L sodium dodecylbenzenesulfonate, 1.5 g / L sodium saccharin and 17.5 g / L sodium sulfate are added to deionized water, 0.1 mol / L sodium hydroxide solution is added dropwise, the pH is adjusted to 9, the temperature is raised to 70°C, the carbon steel sample after pre-nickel plating is suspended in the pre-plating tank, the nickel block is used as the anode, and an auxiliary anode is set, the mechanical stirrer and the air stirring device are turned on, the stirring speed is 120 r / min, and the air flow rate is 8 m 3 / h, turn on the power and set the current density to 6A / dm 2 The electroplating time was 45 min. After the electroplating was completed, the carbon steel test block was washed with deionized water to obtain a nickel-tungsten alloy coating.

[0101] Example 9

[0102] This embodiment is basically the same as embodiment 4, except that, in step (3), the nickel-tungsten alloy layer is electroplated: an electroplating solution is prepared in an electroplating tank, 30 g / L nickel sulfate, 45 g / L sodium tungstate, 45 g / L complexing agent (22.5 g / L sodium citrate, 9 g / L lactic acid and 13.5 g / L triethylenetriamine), 1 g / L rare earth graphene complex, 0.15 g / L sodium dodecylbenzenesulfonate, 1.5 g / L sodium saccharin and 17.5 g / L sodium sulfate are added to deionized water, 0.1 mol / L sodium hydroxide solution is added dropwise, the pH is adjusted to 9, the temperature is raised to 70°C, the carbon steel sample after the nickel layer is pre-plated is hung in the pre-plating tank, the nickel block is used as the anode, and an auxiliary anode is set, the mechanical stirrer and the air stirring device are turned on, the stirring speed is 120 r / min, and the air flow rate is 8 m 3 / h, turn on the power and set the current density to 6A / dm 2 The electroplating time was 45 min. After the electroplating was completed, the carbon steel test block was washed with deionized water to obtain a nickel-tungsten alloy coating.

[0103] The rare earth-graphene composite comes from Preparation Example 2.

[0104] Example 10

[0105] This embodiment is basically the same as embodiment 4, except that, in step (3), the nickel-tungsten alloy layer is electroplated: an electroplating solution is prepared in an electroplating tank, 30 g / L nickel sulfate, 45 g / L sodium tungstate, 45 g / L complexing agent (22.5 g / L sodium citrate, 9 g / L lactic acid and 13.5 g / L triethylenetriamine), 1.2 g / L rare earth graphene complex, 0.15 g / L sodium dodecylbenzenesulfonate, 1.5 g / L sodium saccharin and 17.5 g / L sodium sulfate are added to deionized water, 0.1 mol / L sodium hydroxide solution is added dropwise, the pH is adjusted to 9, the temperature is raised to 70°C, the carbon steel sample after the nickel layer is pre-plated is hung in the pre-plating tank, the nickel block is used as the anode, and an auxiliary anode is set, the mechanical stirrer and the air stirring device are turned on, the stirring speed is 120 r / min, and the air flow rate is 8 m 3 / h, turn on the power and set the current density to 6A / dm 2 The electroplating time was 45 min. After the electroplating was completed, the carbon steel test block was washed with deionized water to obtain a nickel-tungsten alloy coating.

[0106] The rare earth-graphene composite comes from Preparation Example 3.

[0107] Example 11

[0108] This embodiment is basically the same as embodiment 4, except that, in step (3), the nickel-tungsten alloy layer is electroplated: an electroplating solution is prepared in an electroplating tank, 30 g / L nickel sulfate, 45 g / L sodium tungstate, 45 g / L complexing agent (22.5 g / L sodium citrate, 9 g / L lactic acid and 13.5 g / L triethylenetriamine), 1.0 g / L rare earth graphene complex, 0.15 g / L sodium dodecylbenzenesulfonate, 1.5 g / L sodium saccharin and 17.5 g / L sodium sulfate are added to deionized water, 0.1 mol / L sodium hydroxide solution is added dropwise, the pH is adjusted to 9, the temperature is raised to 70°C, the carbon steel sample after the nickel layer is pre-plated is hung in the pre-plating tank, the nickel block is used as the anode, and an auxiliary anode is set, the mechanical stirrer and the air stirring device are turned on, the stirring speed is 120 r / min, and the air flow rate is 8 m 3 / h, turn on the power and set the current density to 6A / dm 2 The electroplating time was 45 min. After the electroplating was completed, the carbon steel test block was washed with deionized water to obtain a nickel-tungsten alloy coating.

[0109] The rare earth-graphene composite comes from Preparation Example 4.

[0110] Example 12

[0111] This embodiment is basically the same as embodiment 10, except that, in step (3), the nickel-tungsten alloy layer is electroplated: an electroplating solution is prepared in an electroplating tank, 30 g / L nickel sulfate, 45 g / L sodium tungstate, 45 g / L chelating agent (22.5 g / L sodium citrate, 9 g / L lactic acid and 13.5 g / L triethylenetriamine), 1.0 g / L rare earth graphene complex, 2 g / L cobalt sulfate, 3 g / L sodium molybdate, 0.15 g / L sodium dodecylbenzenesulfonate, 1.5 g / L sodium saccharin and 17.5 g / L sodium sulfate are added to deionized water, 0.1 mol / L sodium hydroxide solution is added dropwise, the pH is adjusted to 9, the temperature is raised to 70°C, the carbon steel sample after the nickel layer is pre-plated is hung in the pre-plating tank, the nickel block is used as the anode, and an auxiliary anode is set, the mechanical stirrer and the air stirring device are turned on, the stirring speed is 120 r / min, and the air flow rate is 8 m 3 / h, turn on the power and set the current density to 6A / dm 2 The electroplating time was 45 min. After the electroplating was completed, the carbon steel test block was washed with deionized water to obtain a nickel-tungsten alloy coating.

[0112] The rare earth-graphene composite comes from Preparation Example 4.

[0113] Example 13

[0114] This embodiment is basically the same as embodiment 10, except that, in step (3), the nickel-tungsten alloy layer is electroplated: an electroplating solution is prepared in an electroplating tank, 30 g / L nickel sulfate, 45 g / L sodium tungstate, 45 g / L chelating agent (22.5 g / L sodium citrate, 9 g / L lactic acid and 13.5 g / L triethylenetriamine), 1.0 g / L rare earth graphene complex, 4 g / L cobalt sulfate, 6 g / L sodium molybdate, 0.15 g / L sodium dodecylbenzenesulfonate, 1.5 g / L sodium saccharin and 17.5 g / L sodium sulfate are added to deionized water, 0.1 mol / L sodium hydroxide solution is added dropwise, the pH is adjusted to 9, the temperature is raised to 70°C, the carbon steel sample after the nickel layer is pre-plated is hung in the pre-plating tank, the nickel block is used as the anode, and an auxiliary anode is set, the mechanical stirrer and the air stirring device are turned on, the stirring speed is 120 r / min, and the air flow rate is 8 m 3 / h, turn on the power and set the current density to 6A / dm 2 The electroplating time was 45 min. After the electroplating was completed, the carbon steel test block was washed with deionized water to obtain a nickel-tungsten alloy coating.

[0115] The rare earth-graphene composite comes from Preparation Example 4.

[0116] Comparative Example 1

[0117] This comparative example provides a high sulfur-resistant tungsten alloy electroplating anti-corrosion process, comprising the following steps:

[0118] (1) Pretreatment: Fix a carbon steel specimen with a size of 50 mm × 25 mm × 1.8 mm on a rotating fixture and sandblast it. Adjust the compressed air pressure to 0.4 MPa, keep the sandblasting gun head 12 cm away from the pipe surface, and continue for 5 minutes. After sandblasting, blow the surface of the carbon steel specimen with compressed air to remove residual sand and dust, and then transfer the carbon steel specimen to an ultrasonic cleaner for cleaning. Prepare a degreasing solution in a degreasing tank. Add 50 g / L sodium hydroxide, 20 g / L sodium carbonate, 25 g / L trisodium phosphate and 2.0 g / L O-10 surfactant into deionized water, stir evenly and heat to 75 °C. Place the sandblasted carbon steel specimen in the degreasing tank and soak for 10 minutes. During this period, turn the carbon steel specimen every 2 minutes. After the end, take out the carbon steel specimen and rinse it with 60 °C running hot water for 3 minutes. Use a stainless steel plate as the anode and a carbon steel specimen as the cathode. Place them in a solution with the same composition as the chemical degreasing solution. Connect the rectifier and set the current density to 7 A / dm 2 , the temperature is maintained at 65 ° C, the treatment time is 2 minutes, and electrochemical degreasing is performed. After the degreasing is completed, the workpiece is rinsed with running cold water; 18wt% hydrochloric acid solution is prepared in the pickling tank, and the carbon steel test block is immersed in it. It is soaked at room temperature for 4 minutes. The carbon steel test block is taken out and the inner and outer walls of the workpiece are rinsed with running deionized water for 5 minutes;

[0119] (2) Pre-nickel plating: prepare a pre-plating solution in a pre-plating tank, add 90 g / L nickel sulfate, 55 g / L sodium citrate, and 28 g / L boric acid into deionized water, add 0.1 mol / L sodium hydroxide solution dropwise, adjust the pH to 9.0, raise the temperature to 55°C, hang the pretreated carbon steel test block in the pre-plating tank, use the nickel block as the anode, turn on the power supply, and set the current density to 2 A / dm 2 , pre-plating for 10 minutes, after the pre-plating is completed, rinse the surface of the carbon steel test block with deionized water;

[0120] (3) Electroplating of nickel-tungsten alloy layer: prepare the electroplating solution in the electroplating tank, add 25g / L nickel sulfate, 40g / L sodium tungstate, 40g / L chelating agent (16g / L sodium citrate, 4g / L lactic acid and 20g / L triethylenetriamine), 0.1g / L sodium dodecylbenzenesulfonate, 1g / L sodium saccharin and 15g / L sodium sulfate into deionized water, add 0.1mol / L sodium hydroxide solution dropwise, adjust the pH to 8, raise the temperature to 65℃, hang the carbon steel sample after pre-plating nickel layer in the pre-plating tank, use nickel block as anode, set auxiliary anode, turn on the mechanical stirrer and air stirring device, the stirring speed is 120r / min, and the air flow rate is 8m 3 / h, turn on the power and set the current density to 4A / dm 2 , the electroplating time is 60 min. After the electroplating is completed, the carbon steel test piece is washed with deionized water to obtain a nickel-tungsten alloy coating;

[0121] (4) 7.5 mL of 30 wt% ammonia water was mixed with 300 mL of isopropyl alcohol to form a mixed solution. The electroplated carbon steel specimen was immersed in the mixed solution and soaked in a water bath at 45 °C for 50 min. After soaking, 60 g / L of ethyl orthosilicate solution was added and stirred for 4 h using a magnetic stirrer to obtain a carbon steel specimen with a nano-silica coated nickel-tungsten alloy coating.

[0122] (5) A carbon steel specimen coated with nano-silica nickel-tungsten alloy was placed in a tubular furnace and introduced with 300 sccm of argon. The temperature was raised to 800°C at a rate of 5°C / min. The air in the tube was removed and the temperature was continued to rise to 1200°C. The gas was switched to a mixture of methane and argon with a volume ratio of 1:4 at a flow rate of 250 sccm. The reaction was continued for 4 hours and the mixture was cooled to room temperature to obtain a high sulfur-resistant tungsten alloy coating.

[0123] Performance testing

[0124] Testing standards:

[0125] Corrosion resistance test: The high-sulfur-resistant tungsten alloy coatings obtained in Examples 1-13 and Comparative Example 1 were placed in a hydrogen sulfide solution with a mass concentration of 15% and immersed at 90°C for 10 days. After being taken out, the coatings were washed with deionized water, the residual liquid on the surface was dried, and the coatings were weighed to calculate the weight loss rate. At the same time, the high-sulfur-resistant tungsten alloy coatings obtained in Examples 1-13 and Comparative Example 1 were placed in a hydrogen sulfide solution with a mass concentration of 15% and immersed at 90°C. The time when flaking occurred was observed, and the test results are recorded in Table 1.

[0126] Microhardness test: The high sulfur-resistant tungsten alloy coatings obtained in Examples 1-13 and Comparative Example 1 were tested using a microhardness tester with a load of 0.098 N and a time of 30 s. The test results are recorded in Table 1.

[0127] Wear performance test: The high-sulfur-resistant tungsten alloy coatings obtained in Examples 1-13 and Comparative Example 1 were fixed to the sample holder of a wear tester. A load of 10 N was applied, and the sample holder was slowly immersed in a 15% hydrogen sulfide solution at 90°C for 10 days. After removal, the coating was washed with deionized water, the residual liquid on the surface was dried, and the coating was weighed to calculate the weight loss rate.

[0128] Table 1 Performance test data of high sulfur resistant tungsten alloy electroplating anti-corrosion process in Examples 1-13 and Comparative Example 1

[0129]

[0130] Referring to Table 1, in combination with Example 1 and Comparative Example 1, it can be seen that in the present application, nano-alumina is introduced while coating the surface of the nickel-tungsten alloy coating with silicon carbide. On the one hand, alumina reacts slightly with silicon dioxide and the nickel-tungsten alloy to enhance the chemical bonding at the interface; on the other hand, its thermal expansion coefficient is between that of SiC and the nickel-tungsten alloy, which can effectively alleviate the thermal stress mismatch during the cooling process and reduce the risk of interface cracking; in addition, nano-alumina, as a heterogeneous nucleation site, can promote the refinement of SiC grains and further enhance the bonding strength through the mechanical interlocking effect, thereby improving the overall corrosion resistance, hardness and wear resistance of the coating.

[0131] Referring to Table 1, combined with Examples 2 and 4, it can be seen that annealing the product obtained after the carbothermal reduction reaction can promote atomic diffusion at the interface between Al2O3 and the Ni-W alloy, forming a transition layer, further enhancing the bonding force, and reducing the risk of cracking; at the same time, it eliminates the lattice distortion generated during the reaction, refines the SiC / Al2O3 composite particles, improves the uniformity of the coating, and thus improves the overall performance of the coating.

[0132] Referring to Table 1, combined with Examples 4, 7, and 8, it can be seen that the present application effectively combines graphene and rare earth elements through polyethylene glycol. Specifically, polyethylene glycol acts as a bridge molecule, and the oxygen atoms in its ether bonds act as electron donors, forming coordination bonds with rare earth ions. Furthermore, its hydroxyl groups can hydrogen bond or undergo esterification reactions with functional groups on the graphene surface (such as hydroxyl and carboxyl groups). The rare earth elements, acting as heterogeneous nucleation cores, work together with the steric hindrance of graphene to refine grains and increase coating density. The reinforcing phase interaction between rare earth oxides and graphene synergistically improves the coating's hardness, wear resistance, and toughness, while also enhancing corrosion resistance through the dual mechanisms of forming a composite passivation film and isolating corrosive media. The electrocatalytic activity of the rare earth elements and the high conductivity of graphene optimize the electrodeposition process, increasing deposition rate and current efficiency, while also stabilizing the plating solution composition and improving dispersion, thereby enhancing the overall performance of the resulting coating.

[0133] Referring to Table 1, in combination with Examples 10 and 12, it can be seen that the present application adds cobalt sulfate and sodium molybdate to the electroplating solution. Since cobalt and molybdenum can increase the electrode potential of the alloy, the coating is more difficult to be oxidized in a sulfur-containing environment; tungsten forms a hard carbide / boride skeleton to hinder the diffusion and penetration of sulfides; molybdenum easily forms a MoS2 passivation film in an acidic or neutral sulfur-containing medium. The film has good chemical stability, can isolate the contact between sulfur ions and the substrate, and improves the overall corrosion resistance of the coating.

[0134] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A high sulfur resistance tungsten alloy electroplating anti-corrosion process, characterized in that: The following steps are involved: (1) Electroplating the workpiece in a nickel-tungsten alloy plating solution to obtain a nickel-tungsten alloy coating; (2) Using a liquid phase deposition method, a silicon source is used to in situ synthesize nano-silicon dioxide on the surface of the nickel-tungsten alloy coating to obtain a nano-silicon dioxide-coated nickel-tungsten alloy coating; (3) Adding nano-alumina to an ethanol solution, then adding a silane coupling agent, and ultrasonicating to obtain a sol; (4) Under the protection of an inert gas, the aerosol formed by ultrasonic atomization of the sol, methane and the nano-silicon dioxide coated nickel-tungsten alloy coating are subjected to a carbon thermal reduction reaction to obtain a product, and the product is cooled to obtain a high sulfur-resistant tungsten alloy electroplating layer.

2. The high sulfur resistance tungsten alloy electroplating anti-corrosion process according to claim 1, characterized in that: In step (4), the aerosol and methane are simultaneously introduced into the nano-silica-coated nickel-tungsten alloy layer, the temperature during the carbon thermal reduction reaction is 1200-1400°C, the heating rate is 5-10°C / min, the methane flow rate is 50-200sccm, the aerosol spray rate and the methane flow rate ratio is (0.1-0.5):1; the total pressure of the system is 10-100Pa.

3. The high sulfur resistance tungsten alloy electroplating anti-corrosion process according to claim 1, characterized in that: In step (3), the amount of the silane coupling agent added is 0.5%-1.5% of the mass of the nano-alumina; the particle size of the nano-alumina is 50-100 nm, and the mass concentration of the sol is 5%-15%.

4. The high sulfur resistance tungsten alloy electroplating anti-corrosion process according to claim 1, characterized in that: Step (1), the process conditions during electroplating are: temperature of 65-75°C, pH value of 8.0-9.5, current density of 4-8A / dm 2 , the electroplating time is 10-30min.

5. The high sulfur resistance tungsten alloy electroplating anti-corrosion process according to claim 1, characterized in that: In step (4), the product is further annealed before cooling, specifically, the product is annealed in a mixture of hydrogen and argon at 400-600° C. for 0.5-2 h.

6. The high sulfur resistance tungsten alloy electroplating anti-corrosion process according to claim 1, characterized in that: Step (1), the formula of the nickel-tungsten alloy plating solution includes: 25-35 g / L nickel sulfate, 40-50 g / L sodium tungstate, 40-50 g / L complexing agent, 0.1-0.2 g / L sodium dodecylbenzenesulfonate, 1-2.5 g / L sodium saccharin and 15-20 g / L sodium sulfate.

7. The high sulfur resistance tungsten alloy electroplating anti-corrosion process according to claim 6, characterized in that: The formula of the nickel-tungsten alloy plating solution also includes 0.8-1.2 g / L of a rare earth-graphene composite. The rare earth-graphene composite is prepared by adding graphene oxide, a rare earth salt, and polyethylene glycol to a solvent, adjusting the pH to 5-7 under an inert atmosphere, heating to 70-90° C. for reaction for 3-6 hours, and then adding a reducing agent to obtain the rare earth-graphene composite. When the molecular weight of the polyethylene glycol is 4000, the mass ratio of the rare earth salt to the polyethylene glycol is 10:0.5, and the mass ratio of the graphene oxide to the polyethylene glycol is 10:0.5; or the mass ratio of the rare earth salt to the polyethylene glycol is 15:1.5, and the mass ratio of the graphene oxide to the polyethylene glycol is 10:1.5; or the mass ratio of the rare earth salt to the polyethylene glycol is 20:2, and the mass ratio of the graphene oxide to the polyethylene glycol is 10:2; when the molecular weight of the polyethylene glycol is 6000, the mass ratio of the rare earth salt to the polyethylene glycol is 15:1.5, and the mass ratio of the graphene oxide to the polyethylene glycol is 10:1.

5.

8. The high sulfur resistance tungsten alloy electroplating anti-corrosion process according to claim 7, characterized in that: The rare earth salt is one of lanthanum nitrate, cerium sulfate, lanthanum chloride, cerium nitrate, praseodymium acetate, and neodymium fluoride.

9. The high sulfur resistance tungsten alloy electroplating anti-corrosion process according to claim 7, characterized in that: The formula of the nickel-tungsten alloy plating solution also includes 2-4 g / L of cobalt sulfate and 3-6 g / L of sodium molybdate.

10. The high sulfur resistance tungsten alloy electroplating anti-corrosion process according to claim 6, characterized in that: The complexing agent is a mixture of sodium citrate, lactic acid and triethylenetriamine in a mass ratio of (4-6): (1-3): (2-5).

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