A nickel-copper-nickel-nickel tungsten multilayer plating layer and a preparation method thereof

Abstract

The application discloses a nickel-copper-nickel-nickel tungsten multilayer plating layer and a preparation method thereof. After pretreatment of a base material, a nickel bottom layer is obtained by first electroplating nickel, a copper layer is obtained by electroplating copper, a nickel intermediate layer is obtained by second electroplating nickel, a nickel tungsten alloy surface layer is obtained by electroplating a nickel tungsten alloy, and then heat treatment is performed to obtain the nickel-copper-nickel-nickel tungsten multilayer plating layer. When electroplating the nickel tungsten alloy, a titanium base-iridium tantalum oxide coating anode is used, and the electroplating solution for electroplating the nickel tungsten alloy is a citric acid system. In the titanium base-iridium tantalum oxide coating anode, the mass fraction of tantalum is more than 5% higher than the mass fraction of iridium. The corrosion resistance of the plating layer is greatly improved through the cooperation of the multilayer plating layer and the improvement of the quality of the outermost plating layer.

Description

Technical Field

[0001] This invention relates to a nickel-copper-nickel-nickel-tungsten multilayer coating and its preparation method, belonging to the field of electroplating technology. Background Technology

[0002] Nickel-tungsten alloy coatings possess excellent corrosion and wear resistance. Nickel-tungsten alloy technology is widely used in petroleum machinery, marine machinery, engineering machinery, and military industries, and is a key technology in the electrodeposition industry. While tungsten alloys exhibit excellent corrosion and wear resistance, they also have a significant drawback: their corrosion potential is higher than that of ordinary steel substrates. When the tungsten alloy fails, a corrosion potential difference arises between the substrate and the tungsten alloy coating (where the tungsten alloy acts as a cathode), leading to preferential or even accelerated corrosion of the substrate. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the first objective of this invention is to provide a method for preparing a highly corrosion-resistant nickel-copper-nickel-nickel-tungsten multilayer coating. The method of this invention, on the one hand, introduces a copper coating, creating a potential difference between the copper coating and the nickel-tungsten alloy surface layer, thereby transforming the nickel-tungsten alloy coating from a cathodic coating to an anodic coating. On the other hand, by improving the quality of the nickel-tungsten alloy coating, a highly corrosion-resistant nickel-copper-nickel-nickel-tungsten multilayer coating is obtained.

[0004] The second objective of this invention is to provide a nickel-copper-nickel-nickel-tungsten multilayer coating prepared by the above-described preparation method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] This invention discloses a method for preparing a highly corrosion-resistant nickel-copper-nickel-nickel-tungsten multilayer coating. After pretreatment of the substrate, the substrate is subjected to a first electroplating of nickel to obtain a nickel underlayer, an electroplating of copper to obtain a copper layer, a second electroplating of nickel to obtain a nickel intermediate layer, and an electroplating of nickel-tungsten alloy to obtain a nickel-tungsten alloy surface layer. After heat treatment, the nickel-copper-nickel-tungsten multilayer coating is obtained.

[0007] Among them, a titanium-based iridium-tantalum oxide coating anode is used when electroplating nickel-tungsten alloy, and the electroplating solution for electroplating nickel-tungsten alloy is a citric acid system;

[0008] In the titanium-based iridium-tantalum oxide-coated anode, the mass fraction of tantalum is more than 5% greater than the mass fraction of iridium;

[0009] The electroplating solution for the nickel-tungsten alloy has a pH ≥ 7;

[0010] The thickness of the nickel underlayer is 5-30 μm, the thickness of the copper layer is 10-30 μm, the thickness of the nickel intermediate layer is 3-10 μm, and the thickness of the nickel-tungsten alloy surface layer is 15-30 μm.

[0011] The method for preparing a nickel-copper-nickel-nickel-tungsten multilayer coating provided by this invention involves sequentially electroplating nickel, copper, nickel, and a nickel-tungsten alloy to obtain the nickel-copper-nickel-tungsten multilayer coating. Nickel is used as the underlayer primarily to increase adhesion. Copper electroplating on a substrate easily results in a displacement reaction, leading to poor adhesion between copper and the substrate. No displacement reaction occurs between copper and nickel; therefore, nickel is used as the underlayer. A copper plating layer is then applied on top of the nickel underlayer. A potential difference is created between the copper plating layer and the nickel-tungsten alloy surface layer, causing the tungsten alloy plating layer to change from a cathodic coating to an anodic coating. Finally, the copper layer is applied to the surface... A thin nickel intermediate layer is applied to the surface. However, the tungsten alloy plating solution has a low tolerance for copper ions, and copper dissolves in the nickel-tungsten alloy plating solution. Therefore, a nickel intermediate layer is used to prevent the copper layer from dissolving. Finally, a nickel-tungsten alloy surface layer is applied. Since the corrosion potential of the electroplated copper layer is around -0.1V and the corrosion potential of the tungsten alloy is around -0.5V, the corrosion potential between the two is greater than 400mV, which can form a galvanic cell. This preferentially corrodes the nickel-tungsten alloy plating layer, effectively preventing corrosion of the substrate. At the same time, the excellent corrosion resistance and wear resistance of the nickel-tungsten alloy plating layer can significantly improve the service life of the workpiece, especially irregularly shaped parts.

[0012] Meanwhile, due to the strong tendency of electrodeposition and recrystallization in the intermediate copper layer, it is easy to form equiaxed grains with better isotropy. The coarse equiaxed grain structure is a microscopic manifestation of its excellent plasticity and toughness. This structure allows for a large amount of slip and deformation between grains, thereby effectively absorbing and releasing stress from the surface hard coating, making it an ideal stress buffer layer. Tungsten alloy is a coating with relatively high stress. The introduction of the copper coating can effectively reduce the stress concentration of the coating, alleviate the cracking caused by stress concentration in nickel-tungsten multilayer coatings, and further improve the corrosion resistance of the workpiece. Due to the high toughness of the copper layer, the toughness and impact resistance of multilayer coatings are significantly improved, thereby improving the ductility of irregular parts. The improved ductility allows irregular parts to have a certain degree of salt spray resistance after undergoing a certain amount of deformation under external force. In addition, nickel and copper are both face-centered cubic structures with very similar lattice constants and very small lattice mismatch. This excellent lattice matching allows the underlying nickel layer to grow epitaxially or semi-epitaxially on the copper layer, forming a coherent or semi-coherent interface with low interface energy and very strong bonding. Microscopically, the atoms at the interface are neatly arranged with minimal stress concentration. The epitaxial growth of the intermediate nickel and copper grains provides numerous nucleation sites for the nickel-tungsten phase, enabling more uniform and dense deposition of the nickel-tungsten layer. This avoids decreased bonding or porosity caused by uneven nucleation, further enhancing corrosion resistance.

[0013] In addition, to further improve the coating quality of the outer nickel-tungsten alloy layer and enhance its corrosion resistance and wear resistance, a titanium-based iridium-tantalum oxide coating anode is used during the electroplating of the nickel-tungsten coating. By controlling the tantalum content to be higher than the iridium content, the accumulation and decomposition of the complexing agent can be effectively inhibited, thereby ensuring the deposition of the main salt in the plating solution. The electroplating rate is improved by reducing the current density and increasing the current efficiency, which in turn improves the coating performance.

[0014] The preferred embodiment is that the pretreatment process of the substrate is as follows: the steel substrate is subjected to pre-degreasing, water cleaning, sandblasting, water cleaning, electrochemical degreasing, hot water washing, water cleaning, electrochemical activation, and water cleaning in sequence.

[0015] In this invention, the pretreatment of the substrate can be carried out using conventional existing technologies. For example, electrochemical degreasing can be performed by placing the substrate in a sodium hydroxide solution with a concentration of 20-60 g / L and anolyzing it at 40-70°C for 10-30 min. Electrochemical activation can be performed by placing the substrate in an activation solution and activating it at 0-40°C for 20-120 s. The activation solution is a sulfuric acid solution with a mass fraction of 5-25%.

[0016] In a preferred embodiment, the electroplating solution for the first nickel electroplating comprises: 200-500 g / L nickel sulfate, 30-50 g / L nickel chloride, and 30-50 g / L boric acid.

[0017] In a preferred embodiment, during the first nickel electroplating, a nickel anode or a titanium-iridium anode is used, the temperature is 40-60℃, and the current density is 2-6 A / dm³. 2 The pH value is 3.0-4.5.

[0018] In a preferred embodiment, the electroplating solution for electroplating copper comprises: 30-80 g / L copper pyrophosphate, 300-500 g / L pyrophosphate, and 5-30 g / L ammonium citrate.

[0019] In a preferred embodiment, during copper electroplating, a pure copper plate is used as the anode, the temperature is 20-40℃, and the current density is 0.5-2A / dm³. 2 The pH value is 7.0-9.0, and the electroplating time is 40-120 min.

[0020] In a preferred embodiment, the electroplating solution for the second nickel electroplating comprises: 200-500 g / L nickel sulfate, 30-50 g / L nickel chloride, and 30-50 g / L boric acid.

[0021] In a preferred embodiment, during the second nickel electroplating, a nickel anode or a titanium-iridium anode is used, the temperature is 40-60℃, and the current density is 2-6 A / dm³. 2 The pH value is 3.0-4.5, and the electroplating time is 5-12 minutes.

[0022] In a preferred embodiment, the method for preparing the titanium-based iridium-tantalum oxide-coated anode includes the following steps:

[0023] Step 1

[0024] A solution containing tantalum source A is brushed onto a titanium substrate, and then sintered. This brushing-sintering process is repeated to obtain a tantalum-coated titanium substrate.

[0025] Step Two

[0026] The iridium-tantalum oxide coating solution is brushed onto the tantalum-titanium substrate and then sintered. The brushing-sintering process is repeated to obtain the final product.

[0027] The iridium-tantalum oxide coating solution contains tantalum source B, iridium source, and zirconium source;

[0028] In the iridium-tantalum oxide coating solution, the mass ratio of tantalum to iridium is 6-7:4-5.

[0029] Existing titanium-based iridium-tantalum oxide coated anodes are mainly suitable for acidic electroplating processes, with the iridium-tantalum molar ratio controlled at 6-7:4-5. This is because excessive tantalum content can cause the coating to form numerous large cracks. Oxygen released during electrolysis can easily diffuse into the titanium substrate through these cracks, forming a non-conductive titanium oxide passivation film. This not only hinders current conduction but also damages the adhesion between the coating and the substrate, leading to coating peeling. The aforementioned ratio retains the role of tantalum oxide in enhancing coating stability while ensuring sufficient active sites for iridium oxide. However, these titanium-based iridium-tantalum oxide coated anodes are not suitable for alkaline electroplating processes. In alkaline electroplating, the alkaline solution accelerates the dissolution or structural destruction of iridium and tantalum oxides in the coating, significantly shortening the anode's lifespan. Furthermore, the strong catalytic effect of the noble metal (Ir) in the anode can cause the complexing agent to decompose too quickly, leading to an imbalance in the plating solution, reduced current efficiency, and impacting coating quality and plating solution lifespan. Furthermore, the decomposition products generated by the large-scale decomposition of the complexing agent can adversely affect the performance of the coating. Therefore, the plating solution needs to be adsorbed and filtered regularly, which leads to a decrease in production efficiency.

[0030] The method for preparing the titanium-based iridium-tantalum oxide-coated anode provided by this invention involves two coating processes, ensuring that the tantalum content in the titanium-based iridium-tantalum oxide-coated anode is greater than the iridium content by more than 5%. When used in a moderately alkaline citric acid electroplating system, this method effectively inhibits the decomposition of the complexing agent, maintains the stability of the plating solution composition, thereby guaranteeing the coating quality, reducing plating solution maintenance costs, and extending service life. This is because Ta₂O₅ is an inert component with strong chemical stability. It not only stabilizes the contact area between IrO2 and the titanium substrate, but also effectively suppresses the sharp increase in electrode potential that occurs when oxygen evolution reaction occurs on the anode in an electrolyte containing organic matter, leading to the decomposition of organic matter, thereby stabilizing the plating solution composition. In order to avoid the problem of excessive tantalum content causing a large number of large cracks in the coating, this invention first uses a solution containing tantalum source A to brush onto the titanium substrate, and then obtains a highly conductive tantalum β phase through sintering. Then, by adding a zirconium source to the iridium-tantalum oxide coating solution, and then sintering again, the zirconium can effectively refine the coating grains, fill the microcracks in the iridium-tantalum anode, and improve the coating density, avoiding excessive amount leading to coating cracking or decreased conductivity. Thus, under the preparation method of this invention, a dense titanium-based iridium-tantalum oxide coating anode that can be stable in a neutral to alkaline citric acid electroplating system is obtained.

[0031] In a further preferred embodiment, in step one, the solution containing tantalum source A is a tantalum pentachloride solution, wherein the mass fraction of tantalum pentachloride in the tantalum pentachloride solution is 10-15%. The optimal performance is achieved when the mass fraction of tantalum pentachloride in the solution containing tantalum source A is controlled within this range. If the mass fraction is too high, the coating will be uneven after sintering; if the mass fraction is too low, the coating will be too thin, resulting in missed areas and affecting corrosion resistance.

[0032] In a further preferred embodiment, in step one, a solution containing tantalum source A is brushed onto a titanium substrate and then sintered. The brushing-sintering process is repeated 2-5 times, preferably 4-5 times. The sintering temperature is 600-620℃. The holding time for the last sintering is 1-2 hours, and the holding time for the remaining sinterings is 20-30 minutes.

[0033] In this invention, multiple coatings with a solution containing tantalum source A ensure the thickness and density of the coating. The intermediate holding time is controlled at 20-30 minutes to serve as a transition, allowing the tantalum source to transform into oxide and improving growth efficiency. The final holding at 600-620℃ for an extended period ensures complete crystal transformation. Therefore, the holding temperature needs to be effectively controlled. If the temperature is too low, an α phase will form, reducing conductivity, while if it is too high, the density will decrease.

[0034] In a further preferred embodiment, in step two, the tantalum source B in the iridium-tantalum oxide coating solution is tantalum pentachloride, the iridium source is chloroiridium hexahydrate, and the zirconium source is zirconium chloride.

[0035] In a further preferred embodiment, the amount of zirconium chloride added to the iridium-tantalum oxide coating solution is 2%-5% of the total molar amount of tantalum pentachloride and chloroiridium hexahydrate. Controlling the amount of zirconium source added within this range can effectively refine the coating grains, fill microcracks in the iridium-tantalum anode, improve the coating density, and avoid excessive addition that could lead to coating cracking or decreased conductivity.

[0036] In a further preferred embodiment, in step two, the process of obtaining the iridium-tantalum oxide coating solution is as follows: tantalum pentachloride, chloroiridium hexahydrate, and zirconium chloride are added to a mixed solvent of hydrochloric acid and n-butanol, and ultrasonically treated for 30-60 minutes to obtain the solution.

[0037] In a further preferred embodiment, the mass fraction of n-butanol in the iridium-tantalum oxide coating solution is 60%-75%, and the mass fraction of HCl is 5%-15%.

[0038] Further optimization involves the following step: In step two, the iridium-tantalum oxide coating solution is brushed onto the tantalum-titanium substrate, followed by sintering. This brush-coating-sintering process is repeated 10-15 times. The temperature of the final sintering is 450-520℃, and the holding time during the final sintering is 1-2 hours. The temperature of the remaining sintering cycles is 450-530℃, and the holding time during the remaining sintering cycles is 10-30 minutes. This coating-sintering process yields the coating with the optimal performance.

[0039] In a further preferred embodiment, the mass fraction of tantalum in the titanium-based iridium-tantalum oxide coating anode is 13%-56%, and the mass fraction of iridium is 7%-20%.

[0040] In a preferred embodiment, the electroplating solution for the nickel-tungsten alloy comprises: 10-40 g / L nickel sulfate, 15-50 g / L sodium tungstate, 30-80 g / L sodium citrate, 10-40 g / L citric acid, and 10-40 g / L phosphorous acid.

[0041] In a further preferred embodiment, the electroplating solution for the nickel-tungsten alloy comprises: 20-40 g / L nickel sulfate, 20-40 g / L sodium tungstate, 30-60 g / L sodium citrate, 20-40 g / L citric acid, and 10-30 g / L phosphorous acid.

[0042] In a preferred embodiment, the electroplating of the nickel-tungsten alloy is performed at a temperature of 50-80°C and a current density of 5-15 A / dm². 2 The pH value is 7.0-8.0, and the electroplating time is 30-60 minutes.

[0043] Experiments have shown that using a titanium-based iridium-tantalum oxide-coated anode results in higher electroplating efficiency, higher coating quality, and ultimately, superior corrosion and wear resistance.

[0044] In a preferred embodiment, the heat treatment temperature is 180-520℃ and the heat treatment time is 1-4 hours.

[0045] Further preferably, the heat treatment temperature is 180-220℃. Experiments have shown that if the electroplated parts are used in a normal temperature environment, such as a marine environment, the aforementioned lower heat treatment temperature is sufficient.

[0046] Further preferably, the heat treatment temperature is 460-520℃. Experiments have shown that after the electroplated parts are treated at the above-mentioned higher temperatures, the electroplated parts with nickel-copper-nickel-nickel-tungsten multilayer coatings provided by the present invention can be applied to high-temperature and high-pressure environments, such as oil fields and mining operations, and have excellent corrosion resistance.

[0047] The present invention also provides a nickel-copper-nickel-nickel-tungsten multilayer coating prepared by the above preparation method, wherein the nickel-copper-nickel-tungsten multilayer coating refers to a steel substrate surface coated with a nickel underlayer, a copper layer, a nickel intermediate layer, and a nickel-tungsten alloy surface layer in sequence from the inside to the outside.

[0048] In a preferred embodiment, the thickness of the nickel underlayer is 5-30 μm, the thickness of the copper layer is 10-30 μm, the thickness of the nickel intermediate layer is 3-10 μm, and the thickness of the nickel-tungsten alloy surface layer is 15-30 μm.

[0049] Experiments have shown that controlling the thickness of each layer within the above range yields the best final performance. Electroplated copper has a relatively large porosity; if it is too thin, it is prone to perforation corrosion. The main function of the intermediate nickel layer is to cover the copper layer and prevent it from dissolving in the tungsten alloy plating solution. If the thickness of the intermediate nickel layer is too large, it will act as a shield, weakening or eliminating the potential difference between the tungsten alloy and the copper layer, thus failing to play a role in corrosion potential.

[0050] Principles and advantages

[0051] The method for preparing a nickel-copper-nickel-nickel-tungsten multilayer coating provided by this invention involves sequentially electroplating nickel, copper, nickel, and a nickel-tungsten alloy to obtain the nickel-copper-nickel-tungsten multilayer coating. Nickel is used as the underlayer primarily to increase adhesion. Electroplating copper on a steel substrate easily leads to a displacement reaction, resulting in poor adhesion between copper and the substrate. Since copper and nickel do not undergo a displacement reaction, a nickel underlayer is used. A copper plating layer is then applied on top of the nickel underlayer. A potential difference is created between the copper plating layer and the nickel-tungsten alloy surface layer, causing the tungsten alloy plating layer to change from a cathodic coating to an anodic coating. Then, the copper plating layer is applied... A thin nickel intermediate layer is applied to the surface of the plating layer. However, the tungsten alloy plating solution has a low tolerance for copper ions, and copper dissolves in the nickel-tungsten alloy plating solution. Therefore, a nickel intermediate layer is used to prevent the copper layer from dissolving. Finally, a nickel-tungsten alloy surface layer is applied. Since the corrosion potential of the electroplated copper layer is around -0.1V and the corrosion potential of the tungsten alloy is around -0.5V, the corrosion potential between the two is greater than 400mV, which can form a galvanic cell. This preferentially corrodes the nickel-tungsten alloy plating layer, effectively preventing corrosion of the substrate. At the same time, the excellent corrosion resistance and wear resistance of the nickel-tungsten alloy plating layer can significantly improve the service life of the workpiece, especially irregularly shaped parts.

[0052] In addition, to further improve the coating quality of the outer nickel-tungsten alloy layer and enhance its corrosion resistance and wear resistance, a titanium-based iridium-tantalum oxide coating anode is used during the electroplating of the nickel-tungsten coating. The tantalum content is controlled to be higher than the iridium content, which can effectively inhibit the accumulation and decomposition of the complexing agent, thereby ensuring the deposition of the main salt in the plating solution. The electroplating rate is improved by reducing the current density and increasing the current efficiency, thereby improving the coating performance. Attached Figure Description

[0053] Figure 1 The images shown are of the electroplated samples of Example 1, Comparative Example 1, and Comparative Example 2. (a) is an image of sample A in Example 1, (b) is an image of the electroplated sample of Comparative Example 1, and (c) is an image of the electroplated sample of Comparative Example 2.

[0054] Figure 2 The images show the salt spray effect of the samples after electroplating in Examples 1, 2, and 3 for 1000 hours. (a) is the salt spray effect of the sample after electroplating in Example 1 for 1000 hours, (b) is the salt spray effect of the sample after electroplating in Example 2 for 1000 hours, and (c) is the salt spray effect of the sample after electroplating in Example 3 for 1000 hours.

[0055] Figure 3 This is a 480-hour salt spray effect image of the sample containing a nickel-nickel-tungsten multilayer coating in Comparative Example 1.

[0056] Figure 4The images show the effect of the 100 AH Hull tank for the tungsten alloy solution in Example 1 and Comparative Example 2, where (a) is the effect of the 100 AH Hull tank for the tungsten alloy solution in Example 1 and (b) is the effect of the 100 AH Hull tank for the tungsten alloy solution in Comparative Example 2.

[0057] Figure 5 The salt spray effect of the electroplated sample in Comparative Example 3 after 1000 hours.

[0058] Figure 6 The image shows the effect of 800 hours of salt spray on sample C after electroplating in Comparative Example 4. Detailed Implementation

[0059] Example 1

[0060] Step 1: Preparation of the titanium-based iridium-tantalum oxide coated anode:

[0061] Step 11: Clean the titanium substrate (first wash with water, then polish with 800-grit sandpaper) and sandblast (use 80-120 mesh quartz sand, sandblasting pressure is 3.5 kg / cm²). 2 The process includes degreasing (the titanium matrix is ​​placed in an alkaline solution (containing the following components: NaOH 40 g / L, Na2CO3 40 g / L, Na2PO4 40 g / L) to remove oil, with the degreasing temperature controlled at 80℃), water washing, acid washing (hot soaking in an oxalic acid solution at 100℃ for 1 hour, with the oxalic acid mass fraction in the solution being 10%), water washing, and drying.

[0062] Step 12: Dissolve 15% tantalum pentachloride and brush it onto the titanium substrate treated in Step 1. Sinter at 600°C for 20 min. Repeat 4 times. After the last sintering, keep at 600°C for 1 h.

[0063] Step 13: Weigh tantalum pentachloride and chloroiridic acid hexahydrate at a tantalum to iridium mass ratio of 7:5, then weigh zirconium chloride (the mass of zirconium chloride is 5% of the total molar mass of tantalum pentachloride and chloroiridic acid hexahydrate), dissolve in concentrated hydrochloric acid and n-butanol (concentrated hydrochloric acid accounts for 15% of the total mass of the coating solution, and n-butanol accounts for 70% of the total mass of the coating solution), and sonicate for 40 min.

[0064] Step 14, Preparation of titanium-based iridium-tantalum oxide coated anode: The coating solution prepared in step 3 is brushed onto the titanium substrate treated in step 2, sintered at 500℃ for 10 min and then cooled, repeated 10 times. After the last sintering, it is held at 500℃ for 1 h.

[0065] Through the above process, a titanium-based iridium-tantalum oxide-coated anode with a tantalum content of 22.82% and an iridium content of 14.87% was prepared.

[0066] Step 2: Preparation of nickel-copper-nickel-nickel-tungsten multilayer coating:

[0067] Step 21: Preparation of plating solutions for each layer:

[0068] Prepare a nickel solution according to the formula: nickel sulfate: 350 g / L, nickel chloride: 40 g / L, boric acid: 40 g / L, adjust the pH to 3.6, and set aside for later use.

[0069] Prepare a copper solution according to the formula: copper pyrophosphate: 55 g / L, pyrophosphate: 400 g / L, ammonium citrate: 20 g / L, adjust the pH to 8.5, and set aside for later use.

[0070] Prepare a nickel-tungsten alloy solution with the following components: nickel sulfate: 20 g / L, sodium tungstate: 30 g / L, sodium citrate: 40 g / L, citric acid: 20 g / L, and phosphorous acid: 20 g / L. Adjust the pH to 7.0 and set aside for later use.

[0071] Step 22: Take a 50×30×3mm carbon steel sheet and sequentially perform the following steps: pre-degreasing, water rinsing, sandblasting, water rinsing, electrochemical degreasing, hot water rinsing, water rinsing, electrochemical activation, and water rinsing, at a current density of 4A / dm³. 2 Electroplating was performed in a nickel solution at 55℃ for 20 minutes to obtain a nickel layer with a thickness of 15 μm. After cleaning, the layer was plated at a current density of 1 A / dm³. 2 Electroplating was performed in a copper solution at 25℃ for 40 min to obtain a 10 μm copper layer. After cleaning, the layer was plated at a current density of 4 A / dm³. 2 Electroplating was performed in a nickel solution at 55℃ for 5 minutes to obtain a nickel layer with a thickness of 5 μm. After cleaning, the layer was then plated at a current density of 10 A / dm³. 2 Electroplating was performed in a nickel-tungsten alloy solution at 75℃ for 50 minutes to obtain a nickel-tungsten alloy coating with a thickness of 17μm. The plated part was then heat-treated at 200℃ for 2 hours to obtain sample A containing a nickel-copper-nickel-nickel-tungsten multilayer coating. The plated part was then heat-treated at 500℃ for 2 hours to obtain sample B containing a nickel-copper-nickel-nickel-tungsten multilayer coating.

[0072] in, Figure 1 (a) is a physical image of sample A with a nickel-copper-nickel-nickel-tungsten multilayer coating prepared in Example 1. It can be seen from the image that the coating is uniform and bright after electroplating.

[0073] Figure 2 (a) is a neutral salt spray effect diagram of sample A with nickel-copper-nickel-nickel-tungsten multilayer coating in Example 1 after 1000h. It can be seen from the figure that there is no rust at all.

[0074] In addition, a corrosion resistance test was conducted on sample B, which contained a nickel-copper-nickel-nickel-tungsten multilayer coating, in an oil and gas industrial environment (corrosive medium: 15 wt.% NaCl aqueous solution; temperature: 120 ℃, pressure (total pressure) 17.32 MPa, CO2 partial pressure: 5.6 MPa; flow rate: 1.7 m / s). The corrosion rate of sample B containing the nickel-copper-nickel-nickel-tungsten multilayer coating was 0.1005 mm / a.

[0075] Example 2

[0076] The other conditions are the same as in Example 1, except that a 50×30×3 carbon steel sheet is used for pretreatment, and the current density is 4A / dm³. 2 Electroplating was performed in a nickel solution at 55℃ for 20 minutes to obtain a nickel layer with a thickness of 15 μm. After cleaning, the layer was plated at a current density of 1 A / dm³. 2 Electroplating was performed in a copper solution at 25℃ for 85 minutes to obtain a 20μm copper layer. After cleaning, the layer was plated at a current density of 4A / dm³. 2 Electroplating was performed in a nickel solution at 55℃ for 5 minutes to obtain a nickel layer with a thickness of 5 μm. After cleaning, the layer was then plated at a current density of 10 A / dm³. 2 Electroplating was performed in a nickel-tungsten solution at 75°C for 50 minutes to obtain a nickel-tungsten alloy coating with a thickness of 17 μm. Figure 2 (b) in Example 2 shows the salt spray effect of the sample containing a nickel-copper-nickel-nickel-tungsten multilayer coating after 1000 hours. As can be seen from the figure, there is no rust at all.

[0077] Example 3

[0078] The other conditions are the same as in Example 1, except that a 50×30×3 carbon steel sheet is used for pretreatment, and the current density is 4A / dm³. 2 Electroplating was performed in a nickel solution at 55℃ for 20 minutes to obtain a nickel layer with a thickness of 15 μm. After cleaning, the layer was plated at a current density of 1 A / dm³. 2 Electroplating was performed in a copper solution at 25℃ for 125 min to obtain a 30 μm copper layer. After cleaning, the layer was plated at a current density of 4 A / dm³. 2 Electroplating was performed in a nickel solution at 55℃ for 5 minutes to obtain a nickel layer with a thickness of 5 μm. After cleaning, the layer was then plated at a current density of 10 A / dm³. 2 Electroplating was performed in a tungsten solution at 75°C for 50 minutes to obtain a tungsten alloy coating with a thickness of 17 μm. Figure 2 (c) in Example 3 shows the salt spray effect of the sample containing a nickel-copper-nickel-nickel-tungsten multilayer coating after 1000 hours. As can be seen from the figure, there is no rust at all.

[0079] Comparative Example 1

[0080] The other conditions are the same as in Example 1, except that a 50×30×3 carbon steel sheet is used for pretreatment at a current density of 4.5A / dm³. 2 Electroplating was performed in a nickel solution at 55℃ for 40 minutes to obtain a nickel layer with a thickness of 25 μm. After cleaning, the plating was carried out at a current density of 10 A / dm³. 2 Electroplating was performed in a nickel-tungsten solution at 75℃ for 80 minutes to obtain a nickel-tungsten alloy coating with a thickness of 25 μm. Figure 1 Image (b) is a photograph of the sample with a nickel-nickel-tungsten multilayer plating in Comparative Example 1. The plating is uniform and bright after electroplating. Figure 3 The image shows the 480-hour salt spray effect of the sample containing a nickel-nickel-tungsten multilayer coating in Comparative Example 1. It can be seen from the image that the middle part is severely corroded.

[0081] Comparative Example 2

[0082] Other conditions are the same as in Example 1, except that a nickel layer is not placed on the surface of the copper layer, and a 50×30×3mm carbon steel sheet is used for pretreatment at a current density of 4A / dm³. 2 Electroplating was performed in a nickel solution at 55℃ for 20 minutes to obtain a nickel layer with a thickness of 15 μm. After cleaning, the layer was plated at a current density of 1 A / dm³. 2 Electroplating was performed in a copper solution at 25°C for 40 minutes to obtain an 8μm copper layer. After cleaning, the copper layer was plated at a current density of 10A / dm³. 2 Electroplating in a nickel-tungsten solution at 75℃ initially yielded test pieces with excellent performance. However, after 100 ampere-hours of tungsten alloy electroplating, the carbon steel sheets began to blacken. Figure 1 As shown in (c), the main cause is the dissolved copper ions in the tungsten alloy plating solution, while Figure 4 The image shows the effect of the 100 Ah Hull tank of tungsten alloy solution in Example 1 and Comparative Example 2. It can be seen that in Comparative Example 2, since the tungsten alloy solution was directly plated at 100 Ah without electroplating intermediate nickel, the Hull tank changed from 10 cm to 6 cm, indicating that the solution's movement ability was worse and did not meet the usage standards of tungsten alloy.

[0083] Comparative Example 3

[0084] Other conditions were the same as in Example 1, except that a 50×30×3 carbon steel sheet was used for pretreatment at a current density of 4A / dm³. 2 Electroplating was performed in a nickel solution at 55℃ for 20 minutes to obtain a nickel layer with a thickness of 15 μm. After cleaning, the layer was plated at a current density of 1 A / dm³. 2 Electroplating was performed in a copper solution at 25℃ for 40 min to obtain a 9 μm copper layer. After cleaning, the layer was plated at a current density of 4 A / dm³. 2 Electroplating was performed in a nickel solution at 55℃ for 30 minutes to obtain a nickel layer with a thickness of 20 μm. After cleaning, the layer was then plated at a current density of 10 A / dm³. 2Electroplating was performed in a nickel-tungsten solution at 75℃ for 50 minutes to obtain a nickel-tungsten alloy coating with a thickness of 17 μm. Figure 5 The image shows the 1000-hour salt spray effect of the sample containing a nickel-nickel-tungsten multilayer coating in Comparative Example 3. It can be seen that the corrosion is quite severe. In fact, corrosion appeared at about 600 hours, indicating that an excessively thick nickel intermediate layer will reduce the corrosion resistance.

[0085] Comparative Example 4

[0086] Other conditions were the same as in Example 1, except that the titanium-based iridium-tantalum oxide-coated anode prepared in Example 1 was not used; instead, stainless steel was used as the anode. The current density was 4 A / dm³. 2 Electroplating was performed in a nickel solution at 55℃ for 20 minutes to obtain a nickel layer with a thickness of 15 μm. After cleaning, the layer was plated at a current density of 1 A / dm³. 2 Electroplating was performed in a copper solution at 25℃ for 40 min to obtain a 10 μm copper layer. After cleaning, the layer was plated at a current density of 4 A / dm³. 2 Electroplating was performed in a nickel solution at 55℃ for 5 minutes to obtain a nickel layer with a thickness of 5μm. After cleaning, the layer was plated with a stainless steel anode at a current density of 10A / dm². 2 Electroplating was performed in a nickel-tungsten alloy at 75℃ for 50 min to obtain a nickel-tungsten alloy coating with a thickness of 17 μm. The coated part was then heat-treated at 200℃ for 2 h to obtain sample C containing a nickel-copper-nickel-nickel-tungsten multilayer coating. The coated part was then heat-treated at 500℃ for 2 h to obtain sample D containing a nickel-copper-nickel-nickel-tungsten multilayer coating. Figure 6 The image shows the salt spray effect of sample C (containing a nickel-nickel-tungsten multilayer coating) in Comparative Example 4 after 800 hours. Rust has already appeared in the middle position. In addition, sample D (containing a nickel-copper-nickel-nickel-tungsten multilayer coating) was subjected to a corrosion resistance test in an oil and gas industrial environment (corrosive medium: 15 wt.% NaCl aqueous solution; temperature: 120 ℃, pressure (total pressure) 17.32 MPa, CO2 partial pressure: 5.6 MPa; flow rate: 1.7 m / s). The corrosion rate of sample B (containing a nickel-copper-nickel-nickel-tungsten multilayer coating) was 0.1430 mm / a.

Claims

1. A method for producing a highly corrosion resistant nickel-copper-nickel-nickel tungsten multilayer coating, characterized by: After the substrate is pretreated, a nickel underlayer is obtained by first electroplating nickel, a copper layer is obtained by electroplating copper, a nickel intermediate layer is obtained by second electroplating nickel, a nickel tungsten alloy surface layer is obtained by electroplating nickel tungsten alloy, and then a nickel-copper-nickel-nickel tungsten multilayer plating layer is obtained after heat treatment; The titanium-based iridium tantalum oxide coating anode is used in electroplating the nickel tungsten alloy, and the electroplating solution for electroplating the nickel tungsten alloy is a citric acid system; In the titanium-based iridium tantalum oxide coating anode, the mass fraction of tantalum is more than 5% larger than the mass fraction of iridium; The pH of the electroplating solution for electroplating the nickel tungsten alloy is greater than or equal to 7; The thickness of the nickel underlayer is 5-30 μm, the thickness of the copper layer is 10-30 μm, the thickness of the nickel intermediate layer is 3-10 μm, and the thickness of the nickel tungsten alloy surface layer is 15-30 μm; The preparation method of the titanium-based iridium tantalum oxide coating anode comprises the following steps: Step one A solution containing a tantalum source A is brushed on a titanium base, and then sintering is performed, and the brushing-sintering process is repeated 2-5 times, the sintering temperature is 600-620 ℃, the holding time of the last sintering is 1-2 h, and the holding time of the other sintering is 20-30 min; a tantalum-coated titanium base is obtained; Step two An iridium tantalum oxide coating solution is brushed on the tantalum-coated titanium base, and then sintering is performed, and the brushing-sintering process is repeated to obtain the titanium-based iridium tantalum oxide coating anode; The iridium tantalum oxide coating solution contains a tantalum source B, an iridium source and a zirconium source; In the iridium tantalum oxide coating solution, the mass ratio of tantalum to iridium is 6-7:4-5; In the iridium tantalum oxide coating solution, the tantalum source B is pentachloride tantalum, the iridium source is chloroiridate acid hexahydrate, and the zirconium source is zirconium chloride; In the iridium tantalum oxide coating solution, the addition amount of zirconium chloride is 2%-5% of the total molar amount of pentachloride tantalum and chloroiridate acid hexahydrate.

2. The method for preparing high corrosion resistant nickel-copper-nickel-nickel tungsten multilayer coating according to claim 1, characterized in that: The pretreatment process of the steel substrate comprises the following steps: the steel substrate is sequentially subjected to pre-oil removal, water cleaning, sand blasting, water cleaning, electrochemical oil removal, hot water washing, water cleaning, electrochemical activation and water cleaning.

3. The method for preparing high corrosion resistant nickel-copper-nickel-nickel tungsten multilayer coating according to claim 1, characterized in that: The electroplating solution for the first electroplating nickel comprises the following components: nickel sulfate 200-500 g / L, nickel chloride 30-50 g / L and boric acid 30-50 g / L; The first time electroplating nickel, using nickel anode or titanium iridium anode, temperature is 40-60℃, current density: 2-6A / dm 2 , pH 3.0-4.

5.

4. The method according to claim 1, wherein the method is characterized by: The electroplating solution for the electroplating copper comprises the following components: copper pyrophosphate 30-80 g / L, pyrophosphate 300-500 g / L and ammonium citrate 5-30 g / L, The electroplating copper is carried out by using pure copper plate as anode, temperature is 20-40℃, current density is 0.5-2A / dm 2 , pH is 7.0-9.0, and electroplating time is 40-120min. The electroplating solution for the second electroplating nickel comprises the following components: nickel sulfate 200-500 g / L, nickel chloride 30-50 g / L and boric acid 30-50 g / L; The second time electroplating nickel, using nickel anode or titanium iridium anode, temperature is 40-60℃, current density: 2-6A / dm 2 , pH 3.0-4.5, electroplating time is 5-12min.

5. The preparation method of the nickel-copper-nickel-nickel tungsten multilayer plating layer according to claim 4, characterized in that: In step one, the solution containing the tantalum source A is a pentachloride tantalum solution, and the mass fraction of pentachloride tantalum in the pentachloride tantalum solution is 10-15%; In step two, the process for obtaining the iridium tantalum oxide coating solution is as follows: pentachloride tantalum, chloroiridate acid hexahydrate and zirconium chloride are added into a mixed solvent of hydrochloric acid and n-butanol, and ultrasonic treatment is performed for 30-60 min to obtain the iridium tantalum oxide coating solution; In the iridium tantalum oxide coating solution, the mass fraction of n-butanol is 60%-75%, and the mass fraction of HCl is 5%-15%. In step two, the iridium-tantalum oxide coating solution is brushed on the tantalum-coated titanium substrate, and then sintered, and the brushing-sintering is repeated for 10-15 times, the temperature of the last sintering is 450-520 DEG C, the holding time of the last sintering is 1-2 h, the temperature of the rest sintering is 450-530 DEG C, and the holding time of the rest sintering is 10-30 min.

6. The method according to claim 4, wherein the method is characterized by: In the titanium substrate-iridium-tantalum oxide coating anode, the mass fraction of tantalum is 13%-56%, and the mass fraction of iridium is 7%-20%.

7. The method according to claim 1, wherein the method is characterized by: The electroplating solution for electroplating nickel-tungsten alloy comprises the following components: nickel sulfate 10-40 g / L, sodium tungstate 15-50 g / L, sodium citrate 30-80 g / L, citric acid 10-40 g / L, and phosphorous acid 10-40 g / L; The temperature is 50-80℃, the current density is 5-15A / dm 2 , the pH is 7.0-8.0, and the plating time is 30-60min.

8. The method according to claim 1, wherein the method is characterized by: The temperature of the heat treatment is 180-520 DEG C, and the time of the heat treatment is 1-4 h.

9. A high corrosion resistant nickel-copper-nickel-nickel tungsten multilayer coating prepared according to the method of any one of claims 1-8, characterized in that: The nickel-copper-nickel-nickel tungsten multilayer coating refers to a nickel bottom layer, a copper layer, a nickel intermediate layer and a nickel tungsten alloy surface layer which are sequentially plated on the surface of a steel substrate from inside to outside. The thickness of the nickel bottom layer is 5-30 mu m, the thickness of the copper layer is 10-30 mu m, the thickness of the nickel intermediate layer is 3-10 mu m, and the thickness of the nickel tungsten alloy surface layer is 15-30 mu m.

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