Brush plating solution and brush plating process for repairing tungsten alloy electroplated layer

Abstract

The invention discloses a brush plating solution and a brush plating process for repairing a tungsten alloy electroplated coating, and the preparation process of the brush plating solution comprises the following steps: adding sodium tungstate, sodium citrate, citric acid, nickel sulfate and sodium hypophosphite into deionized water, heating, stirring and dissolving, and adjusting the pH value to 7.0-9.0 to obtain a basic solution; the method comprises the following steps: cleaning SiC particles with deionized water, settling, filtering, adding the settled and filtered SiC particles into a basic solution, adding deionized water, and stirring at a constant volume to obtain the brush plating solution. According to the method, SiC particles are added into the basic solution to be doped and co-deposited into the brush plating layer, good polishing and composite strengthening effects can be achieved, the plating layer which has good corrosion resistance and abrasion resistance, has the hardness reaching 650 HV or above and is flat, smooth and compact is obtained, the method capable of conducting on-site local repairing on the tungsten alloy is obtained, operation is easy, efficiency is improved, and the method is suitable for large-scale popularization and application. And the components and performance of the coating are equivalent to those of a common nickel-tungsten alloy coating, and the service life of a product is not affected.

Description

Technical Field

[0001] The invention relates to the technical field of brush plating, and in particular to a brush plating liquid and a brush plating process for repairing a tungsten alloy electroplating layer. Background Art

[0002] Tungsten alloys include alloys composed of two or three of Fe, Ni, W, and P obtained by electrodeposition, especially nickel-tungsten based binary or multi-element alloys. Because of their superior coating performance, excellent corrosion resistance and wear resistance, and environmental friendliness, they can effectively replace chrome plating and are widely used in the fields of oil production, surface protection of hydraulic machinery, and decorative plating.

[0003] However, during the use of workpieces, such as in oil fields, tungsten alloy coated oil casing, sucker rods and other products will experience partial wear during downhole operations, causing local defects and thus causing the workpiece to be scrapped. If they continue to be used downhole, the products will suffer from local pitting in the downhole medium, thus affecting the overall life of the product and the safety of the pipe column. At the same time, during the electroplating process of the workpiece, problems such as local peeling, plating leakage, pinholes and insufficient size may occasionally occur, resulting in workpiece non-conformity. Conventional surface repair methods such as brushing organic coatings or paints cannot achieve the anti-corrosion effect of tungsten alloys, so users often use new parts for replacement and return damaged parts to the factory for reprocessing, which is costly and inefficient. There is an urgent need for a simple on-site repair method to solve this problem.

[0004] Brush plating is a commonly used local repair solution, often used to repair local damage or dimensional deviation of workpieces. It is an effective way to solve product failures and extend product service life. There are many types of brush plating in common use, but there is no brush plating process that is specifically used for repairing tungsten alloy coatings with similar composition and performance. Tungsten alloy coatings have been verified through a large number of tests to have excellent corrosion resistance and wear resistance in complex working conditions in oil and gas fields and marine environments. Compared with conventional nickel plating, chromium plating, zinc plating and other coatings, the comprehensive performance advantages are obvious. Among them, tungsten content is an important factor affecting the performance of the coating. Commonly used high tungsten content alloy coatings (tungsten content above 5%, especially above 12%) are prepared in neutral or alkaline plating solutions. In order to ensure the density and good performance of the coating, the plating speed used in electroplating is relatively low. The use of electroplating plating solution for brush plating cannot meet the purpose of rapid repair. Summary of the invention

[0005] The technical problem to be solved by the present invention is that there is no simple and effective method to repair the tungsten alloy coating on the surface of a workpiece at the use site. The purpose is to provide a brush plating solution and a brush plating process for repairing the tungsten alloy electroplating layer, so as to obtain a coating with good corrosion resistance and wear resistance, a hardness of more than 650HV of the tungsten alloy coating, a flat, smooth and dense coating, and a method for on-site local repair of tungsten alloy, which is simple to operate, improves efficiency and reduces costs.

[0006] The first object of the present invention is to provide a brush plating solution for repairing tungsten alloy electroplating layers, which is prepared by the following method:

[0007] Add sodium tungstate, sodium citrate, citric acid, nickel sulfate, and sodium hypophosphite to deionized water, heat and stir to dissolve, and adjust the pH value to 7.0-9.0 to obtain a basic solution;

[0008] The SiC particles are washed with deionized water, filtered after sedimentation, and the SiC particles after sedimentation and filtration are added into the basic solution, and deionized water is added to make up the volume and stirred to obtain a brush plating solution.

[0009] In the present invention, sodium tungstate, sodium citrate, citric acid, nickel sulfate, and sodium hypophosphite are mixed and adjusted to an alkaline system to obtain a basic solution, and then SiC particles are added to the basic solution for doping and co-deposition into the coating, which can play a good composite strengthening role, and the ultra-high hardness of SiC is used to further improve the wear resistance of the coating, and the hardness of the original tungsten alloy coating is reached above 650HV, the hardness of the obtained brush-plated coating is high, and the SiC particles also have a polishing effect during the brush plating process, and the obtained brush-plated coating is flat and smooth. The sodium hypophosphite used in the brush plating solution has a strong chemical reduction effect, which can significantly improve the plating rate during brush plating, and cooperates with SiC to improve the density of the coating at a faster brush plating rate, so as to avoid the graying phenomenon of the coating, and make the coating smoother and denser.

[0010] In some optional embodiments, the plating solution contains sodium tungstate at a concentration of 20 to 60 g / L, sodium citrate at a concentration of 20 to 80 g / L, citric acid at a concentration of 20 to 50 g / L, nickel sulfate at a concentration of 10 to 60 g / L, sodium hypophosphite at a concentration of 2 to 20 g / L, and SiC particles at a concentration of 5 to 40 g / L.

[0011] In some optional embodiments, the base plating solution contains 30-50 g / L sodium tungstate, 40-60 g / L sodium citrate, 20-40 g / L citric acid, 30-50 g / L nickel sulfate, 5-10 g / L sodium hypophosphite, and 10-30 g / L SiC particles.

[0012] The sodium hypophosphite used in the present invention has a strong chemical reduction effect, which can significantly improve the plating rate during brush plating. The higher the content of sodium hypophosphite, the faster the plating speed, but the tungsten content in the coating will be significantly reduced. Therefore, it is preferred to control the content of sodium hypophosphite to 5-10g / L to ensure the tungsten content in the coating. If the amount of SiC particles added is too low, the friction coating effect will not be achieved. If it is too high, the plating speed and the roughness of the coating will be affected, and the decomposition of sodium hypophosphite will be accelerated, which will reduce the stability of the plating solution. Therefore, it is preferred to control the amount of SiC particles added to 10-30g / L.

[0013] In some optional embodiments, the particle size of the SiC particles is 0.5-5 μm, and ammonia water is used to adjust the pH value in the basic solution. Selecting the particle size of the SiC particles to be 0.5-5 μm can have a good friction coating effect, and does not affect the plating speed and the roughness of the coating, and does not accelerate the decomposition of sodium hypophosphite, and does not affect the stability of the brush plating solution.

[0014] The second object of the present invention is to provide a brush plating process for repairing tungsten alloy electroplating layers, wherein the brush plating liquid as described in any of the above items is used for brush plating, and the brush plating layer formed after brush plating is composed of the following contents: SiC: 3-15wt%, P: 3~10wt%, W: 5~25wt%, and Ni: the remainder.

[0015] In some optional embodiments, the hardness of the brush-plated layer formed after brush plating is 650-1100 Hv.

[0016] The brush plating process of the present invention can obtain a brush-plated layer with a bright surface and good corrosion resistance. The composition is similar to that of the commonly used nickel-tungsten alloy coating, avoiding the influence of galvanic corrosion. The hardness of the original tungsten alloy coating is above 650HV, and the brush plating can be directly performed on the workpiece to improve the corrosion resistance and wear resistance of the workpiece. It can also be used to repair defects of the tungsten alloy coating during electroplating. This process can realize on-site repair of defects generated during the use of tungsten alloy-plated products. Since tungsten alloy products are generally baked or heat-treated before leaving the factory, the coating has a high hardness. The hardness and wear resistance of the composite tungsten alloy coating reinforced by the brush-plated SiC particles in the present invention are closer to the tungsten alloy layer on the surface of the product, and no post-processing is required to achieve the optimal repair effect, reducing the number of processes and improving efficiency.

[0017] In some optional embodiments, the following steps are performed:

[0018] Heat the brush plating solution to 55-85°C;

[0019] Pre-treat the parts to be repaired. The pre-treatment process includes: grinding, degreasing, activation, and cleaning;

[0020] Use a brush pen to dip into the heated brush plating liquid to perform brush plating on the pre-treated repaired parts;

[0021] After brush plating, rinse and blow dry.

[0022] In some optional embodiments, during the pretreatment process, firstly, different types of sandpaper are used to grind and shape the surface defects of the part to be brush plated in order from coarse to fine, until the part to be brush plated and the surrounding coating are in a smooth transition state, the coarse sandpaper is used for grinding and flattening, and the fine sandpaper is used for polishing;

[0023] Then use degreasing agent to clean, water to wash and dilute acid to activate;

[0024] Then rinse with water and proceed with brush plating.

[0025] In some optional embodiments, the brush plating power supply is a high-frequency switching power supply, and voltage stabilization is set during brush plating, the voltage is set at 4 to 15 V, and the brush plating speed is 60 to 80 μm / h.

[0026] In some optional embodiments, the anode material used for brush plating is a 316 stainless steel plate or an iridium tantalum oxide electrode plate;

[0027] The anode plate is made into a plate, semicircle or rod shape that can fit tightly to the brush-plated part of the workpiece to be repaired. A round rod of the same material is welded in the middle of the back of the anode plate as a conductive handle, and the anode is wrapped with cotton cloth. The conductive handle is connected to a copper wire to form a brush pen for brush plating.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] (1) The present invention adopts sodium tungstate, sodium citrate, citric acid, nickel sulfate, and sodium hypophosphite to mix and adjust to an alkaline system to obtain a basic solution, and then SiC particles are added to the basic solution for doping and co-deposition into the coating, which can play a good composite strengthening role, and the ultra-high hardness of SiC is used to further improve the wear resistance of the coating, and the hardness of the original tungsten alloy coating is above 650HV, and the hardness of the obtained brush-plated coating is high. SiC particles also have a polishing effect during the brush plating process, and the obtained brush-plated coating is flat and smooth. The sodium hypophosphite used in the brush plating solution has a strong chemical reduction effect, which can significantly improve the plating rate during brush plating, and cooperates with SiC to improve the density of the coating at a faster brush plating rate, so as to avoid the graying phenomenon of the coating, make the coating smoother and denser, and form a high-tungsten content alloy coating with good performance on the surface of the workpiece by brush plating.

[0030] (2) The brush plating process provided by the present invention adopts the above-mentioned brush plating solution, and the obtained brush plating layer has a bright surface and good corrosion resistance. The composition is similar to the commonly used nickel-tungsten alloy plating with a high tungsten content, avoiding the influence of galvanic corrosion. The hardness of the original tungsten alloy plating layer is above 650HV, and the brush plating can be directly performed on the workpiece to improve the corrosion resistance and wear resistance of the workpiece, and can also be used to repair the defects of the tungsten alloy plating layer during electroplating.

[0031] (3) The brush plating process of the present invention can realize on-site repair of defects generated during the use of tungsten alloy plated products. Since tungsten alloy products are generally baked or heat treated before leaving the factory, the coating hardness is high. The hardness and wear resistance of the composite tungsten alloy coating reinforced by SiC particles brush-plated in the present invention are closer to the tungsten alloy layer on the surface of the product. No post-processing is required to achieve the optimal repair effect, thereby reducing the number of steps and improving efficiency.

[0032] (4) The brush plating process of the present invention is carried out in an alkaline plating solution, which has low corrosiveness. Commonly used stainless steel materials can be used as anodes, which are simple to manufacture and low in cost. Of course, in order to avoid anode dissolution and consumption, the present invention recommends 316 stainless steel and iridium tantalum tungsten oxide anodes with better corrosion resistance.

[0033] (5) The brush plating process of the present invention adopts a wide voltage range. Although the concentration of metal particles in the plating solution is not high, due to the friction of the particles, the coating is not easily burned under high voltage, which is beneficial to improving the plating speed and repair efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0035] Figure 1 A schematic structural diagram of a brush pen for brush plating provided in one embodiment of the present invention;

[0036] Figure 2 A schematic structural diagram of a brush pen for brush plating provided in another embodiment of the present invention;

[0037] Figure 3 A schematic structural diagram of a brush pen for brush plating provided by another embodiment of the present invention;

[0038] Figure 4 This is a scanning electron microscope image of the tungsten alloy brush-plated layer obtained after brush plating in Example 1 of the present invention;

[0039] Figure 5This is a comparison diagram of the test structures of the corrosion test performed after brush plating in Example 1 of the present invention;

[0040] Figure 6 This is a graph showing the morphology of the coating after the sample is bent after brush plating in Example 1 of the present invention;

[0041] Figure 7 This is a test diagram of coating hardness at different temperatures after brush plating in Example 1 of the present invention;

[0042] Figure 8 This is a scanning electron microscope image of the tungsten alloy brush-plated layer obtained after brush plating in Example 2 of the present invention;

[0043] Fig. 9 This is a diagram showing the inner wall of the oil pipe after brush plating in Example 2 of the present invention;

[0044] Fig.10 This is a diagram showing the outer wall of the oil pipe after brush plating in Example 3 of the present invention;

[0045] Fig.11 This is a friction coefficient curve of the NiWP-SiC and tungsten alloy coatings after brush plating in Example 3 of the present invention. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The illustrative embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0047] In order to solve the problem that the existing process cannot perform on-site local repair of the tungsten alloy electroplating layer, the present invention adopts a brush plating solution and a brush plating process to solve the above problem. The following technical solutions are specifically adopted:

[0048] The present invention first provides a brush plating solution, and the preparation process of the brush plating solution is as follows:

[0049] First add deionized water, then add sodium tungstate, sodium citrate, citric acid, nickel sulfate, sodium hypophosphite, heat and stir to dissolve, adjust the pH value to 7.0-9.0, and obtain a basic solution. In addition, wash the SiC particles with deionized water, filter after sedimentation, and repeat 3 times; then add the washed particles to the basic solution, add deionized water to the fixed volume and stir, and then heat and brush plate;

[0050] In the formed brush plating solution, the mass of sodium tungstate per 1L of brush plating solution is 20-60g, the mass of sodium citrate is 20-80g, the mass of citric acid is 20-50g, the mass of nickel sulfate is 10-60g, the mass of sodium hypophosphite is 2-20g, and the mass of SiC particles is 5-40g. Further, in the brush plating solution, the concentration of sodium tungstate is 30-50g / L, the concentration of sodium citrate is 40-60g / L, the concentration of citric acid is 20-40g / L, the concentration of nickel sulfate is 30-50g / L, the concentration of sodium hypophosphite is 5-10g / L, and the amount of SiC particles added is 10-30g / L.

[0051] Furthermore, the particle size of the SiC particles is 0.5 to 5 μm, and ammonia water is used to adjust the pH value of the basic solution.

[0052] The present invention further provides a brush plating process, using the above brush plating solution for brush plating, and the specific brush plating process is as follows:

[0053] (1) Heat the above brush plating solution to 55-85°C;

[0054] (2) Pre-treatment of the repaired parts: grinding, degreasing, activation, and cleaning;

[0055] (3) Brush plating: After the repaired parts are pre-treated, a brush is used to dip into the brush plating liquid heated in (1) to perform brush plating on the pre-treated repaired parts; after the brush plating is completed, rinse and blow dry.

[0056] Furthermore, in (2), firstly, different types of sandpaper are used from coarse to fine (120#-400#-800#) to grind and repair the surface defects of the part to be brush plated in sequence until the part to be brush plated and the surrounding coating present a smooth transition state, the coarse sandpaper is used for grinding and flattening, and the fine sandpaper is used for polishing; then, a degreaser is used for cleaning, water washing and dilute acid activation; then, water washing is carried out to clean, and then brush plating can be carried out.

[0057] Furthermore, in (3), the speed of the brush pen relative to the workpiece and the brush plating voltage are determined according to the size of the workpiece to be brush plated and the brush plating area. The process parameters are selected so as to maintain the maximum brush plating current while preventing the brush plating surface from becoming gray.

[0058] The anode material used for brush plating is 316 stainless steel plate or iridium tantalum oxide electrode plate. The anode is made into a plate, semicircle or rod shape that can fit tightly according to the shape of the brush-plated part of the workpiece, and then a round rod of the same material is welded in the middle of the back as a conductive handle. The conductive handle consists of a handle and a conductive rod (i.e., the connection point of the wire). The anode is then wrapped with cotton cloth, and the conductive handle is connected to a copper wire to make a brush pen for brush plating. When brush plating, connect the brush pen to the positive pole of the power supply with a copper wire, and connect the workpiece to be plated with a copper wire to the negative pole of the power supply. Turn on the power supply, adjust the voltage to 4-15V, and then start the power supply. Dip the brush pen in the plating solution, close to the part of the workpiece to be plated, move back and forth about 10 times, dip the brush pen in the plating solution again and repeat this action. Design the continuous brush plating time according to the thickness requirements of the repaired coating. The average plating speed of brush plating can reach 60-80μm / h.

[0059] Furthermore, the brush-plated layer formed after brush plating is composed of the following substances: SiC: 3-15wt%, P: 3-10wt%, W: 5-25wt%, Ni: balance. The hardness of the formed brush-plated layer is 650-1100Hv, achieving the anti-corrosion and wear-resistant performance of the original plating layer.

[0060] The present patent application is described in more detail below.

[0061] Example 1: Brush plating of flat sample

[0062] (1) Flat specimen brush plating: suitable for brush plating protection or defect repair on the flat surface of the product.

[0063] (2) Brush pen production: Use 316 stainless steel flat plate as anode. The width of the flat plate is close to the width of the brush plating part. Weld the conductive handle. The shape is as shown in the attached figure. Figure 1 , wrap the anode with cotton cloth, and finally wrap it tightly with cotton thread and connect the wire to make a brush pen suitable for flat brush plating.

[0064] (3) Preparation of brush plating solution: According to the formula of brush plating solution - 30 g / L sodium tungstate, 60 g / L sodium citrate, 20 g / L citric acid, 50 g / L nickel sulfate, 10 g / L sodium hypophosphite, prepare brush plating solution, adjust pH to 8.0 with ammonia water, add 10 g / L 5 μm SiC particles to the plating solution after washing, stir to constant volume, heat to 75 ° C, and stir the solution continuously by magnetic or mechanical means to keep the particles suspended.

[0065] (4) Clean and level the brush-plated area:

[0066] Use 400# or 800# water sandpaper to grind the area to be plated flat and smooth.

[0067] (5) Degreasing, cleaning and activation

[0068] Use 2-3% metal cleaning agent solution to repeatedly scrub the brush-plated parts of the workpiece, and after washing with clean water, the surface will form a uniform water film. Then use cotton cloth dipped in dilute sulfuric acid to repeatedly scrub and activate for 2 minutes, and rinse with water.

[0069] (6) Selection of brush plating voltage

[0070] Voltage range: 4-15V. Start brush plating from low voltage, gradually increase the voltage, and adjust the voltage to the maximum while ensuring the bright coating to improve brush plating efficiency. If the brush-plated coating is gray or black, stop brush plating, use sandpaper to polish the coating until it is semi-bright, speed up the brush pen or reduce the voltage, and then continue brush plating.

[0071] (7) Brush plating method

[0072] The brush pen is dipped in the brush plating liquid and moves back and forth at a speed of 0.2 to 0.5 m / s for rotary brush plating.

[0073] (8) Grinding and leveling during brush plating

[0074] Normally brush plating for 10 minutes, use 400# water sandpaper to polish the brush-plated parts, and properly adjust the movement direction and strength of the brush pen to make the brush-plated layer naturally connected with the surrounding unplated parts, flat and smooth. After 40 minutes of brush plating, if the coating is white, use 800# and 1500# sandpaper to polish or polish until it is bright.

[0075] (9) After brush plating, rinse with water and blow dry to form a NiWP-SiC coating.

[0076] Example 1 Results:

[0077] The plate after brush plating is flat and smooth, with no obvious signs of repair. The thickness of the brush plating layer is 40-50μm. The brush plating layer is observed by scanning electron microscope, and the microscopic morphology is shown. Figure 4 ,Depend on Figure 4 It can be seen that the coating surface is flat and SiC particles are uniformly doped in the coating. The coating composition is detected to be SiC: 8wt%, P: 6wt%, W: 8wt%, and Ni balance.

[0078] After CASS salt spray corrosion test, there is no rust for 96 hours. See the photos before and after corrosion. Figure 5 .

[0079] After brush plating, the sample was bent and the coating did not fall off. Figure 6 The results show that the coating of the plate after brush plating has good bonding with the workpiece surface. Due to the high hardness of the coating, the coating hardness is about 650HV in the plating state and can reach 1100HV after heat treatment. The coating hardness at different temperatures is shown in Figure 7 The coating is very brittle and cracks when bent.

[0080] Example 2: Brush plating repair of the inner wall of the oil casing pipe mouth

[0081] (1) Product failure: The tungsten alloy coating on the inner surface (inner arc surface) of the casing is partially peeling

[0082] (2) Brush pen production: Use iridium tantalum oxide electrode plate to bend into a shape close to the curvature of the inner surface of the casing as the anode. The width of the anode is close to the width of the brush plating part. Weld the conductive handle. The shape is as shown in the attached figure. Figure 2 , wrap the anode with cotton cloth, and finally wrap it tightly with cotton thread, connect the wire, and make a brush pen suitable for brush plating on concave or inner arc surface.

[0083] (3) Preparation of brush plating solution: Prepare brush plating solution according to the formula of brush plating solution - 40 g / L sodium tungstate, 60 g / L sodium citrate, 20 g / L citric acid, 40 g / L nickel sulfate, 7 g / L sodium hypophosphite. Adjust pH to 7.5 with ammonia water. Add 20 g / L 0.5 μm SiC particles to the plating solution after washing with water. Stir to constant volume and heat to 75 °C. Stir the solution continuously by magnetic or mechanical means to keep the particles suspended.

[0084] (4) Clean and level the brush-plated area:

[0085] Use 120# corundum sandpaper and 400# water sandpaper to grind the peeling parts, especially the edges, to make them smooth.

[0086] (5) Degreasing, cleaning and activation

[0087] Use 2-3% metal cleaning agent solution to repeatedly scrub the brush-plated parts of the workpiece, and after washing with clean water, the surface will form a uniform water film. Then use a clean cotton cloth dipped in dilute sulfuric acid to repeatedly scrub and activate for 2 minutes, and rinse with water.

[0088] (6) Selection of brush plating voltage

[0089] Voltage available range: 4-8V. Start brush plating from low voltage, gradually increase the voltage, and adjust the voltage to the maximum while ensuring the bright coating to improve brush plating efficiency. If the brush-plated coating turns gray or black, stop brush plating, use sandpaper to polish the coating until it is semi-bright, reduce the voltage, and then continue brush plating.

[0090] (7) Brush plating method

[0091] The brush moves back and forth left and right at the part to be plated at a speed of 0.1-0.2m / s.

[0092] (8) Grinding and leveling during brush plating

[0093] Normally brush plating for 10 to 15 minutes, use 800# water sandpaper to polish the brush-plated parts, especially the edges, and properly adjust the movement direction and strength of the brush pen to make the brush-plated layer naturally connected with the surrounding un-brush-plated parts, smooth and flat, without gaps or steps, and then continue brush plating. The brush plating time is about 50 minutes.

[0094] (9) Post-processing

[0095] If the brush-plated layer is inconsistent with the original plating layer in color, it can be polished with 1500# sandpaper, and then the workpiece can be wiped dry with cotton cloth and then it can be used as a finished product for subsequent processing or packaging.

[0096] Example 2 Results:

[0097] The microstructure of the brush-plated layer is shown in Figure 8 , the surface is flat and the SiC particles are evenly distributed.

[0098] There is no obvious sign of repair on the inner wall of the repaired casing mouth, the brush plating thickness is 40-50μm, and the plating hardness is 670Hv.

[0099] The repaired parts were tested for porosity using the iron reagent method and corrosion test using 5% NaCl solution. The test results showed that the coating porosity was 0, indicating that the coating was dense and completely covered the damaged parts. The corrosion test lasted for 96 hours without rust. Fig. 9 .

[0100] The brush-plated layer was tested for bonding strength using the 300°C thermal shock method, and there was no peeling. The repair was qualified.

[0101] Example 3: Brush plating repair of the outer wall of the oil pipe

[0102] (1) Product failure: local coating damage on the outer surface of the oil pipe

[0103] (2) Brush pen production: Use 316 stainless steel plate to bend into a shape close to the curvature of the outer wall of the oil pipe as the anode. The width of the anode is close to the width of the brush plating part. Weld the conductive handle. The shape is as shown in the attached figure. Figure 3 , wrap the anode with cotton cloth, and finally wrap it tightly with cotton thread, connect the wire, and make a brush pen suitable for brush plating on concave or inner arc surface.

[0104] (3) Preparation of brush plating solution: According to the formula of brush plating solution - 50 g / L sodium tungstate, 40 g / L sodium citrate, 20 g / L citric acid, 30 g / L nickel sulfate, 5 g / L sodium hypophosphite, prepare brush plating solution, adjust pH to 7.5 with ammonia water, add 30 g / L 3 μm SiC particles to the plating solution after washing, stir to constant volume, heat to 75 ° C, and stir the solution continuously by magnetic or mechanical means to keep the particles suspended.

[0105] (4) Clean and level the brush-plated area:

[0106] Use 120-mesh sandpaper and 400- and 800-mesh water sandpaper to grind the damaged area and the interface with the original coating to make it smooth.

[0107] (5) Degreasing, cleaning and activation

[0108] Use metal cleaning agent solution to repeatedly scrub the brush-plated parts of the workpiece, and after washing with clean water, the surface will form a uniform water film. Then use cotton cloth dipped in dilute sulfuric acid to repeatedly scrub and activate for 2 minutes, and rinse with water.

[0109] (6) Selection of brush plating voltage

[0110] The power supply voltage range is 4-12V. Use a brush pen to dip into the plating solution and start brush plating from low voltage, gradually increase the voltage, and adjust the voltage to the maximum while ensuring the bright coating to improve the efficiency of brush plating. If the brush-plated coating is gray or black, stop brush plating, use sandpaper to polish the coating until it is semi-bright, speed up the brush pen or reduce the voltage, and then continue brush plating.

[0111] (7) Brush plating method

[0112] The brush moves back and forth on the part to be repaired at a speed of 0.2 to 0.5 m / s.

[0113] (8) Grinding and leveling during brush plating

[0114] Normally brush plating for 10 to 15 minutes, use 800# water sandpaper to polish the brush-plated parts, especially the edge of the damaged parts, and properly adjust the movement direction and strength of the brush pen to make the brush-plated layer naturally connected with the surrounding un-brushed parts, smooth and flat, without gaps or steps. Continue brush plating. The brush plating time is about 40 minutes.

[0115] (9) Post-processing

[0116] If the brush-plated layer is inconsistent with the original plating layer in color, it can be polished with 1500# sandpaper or mechanically polished, and then the oil pipe can be cleaned.

[0117] Example 3 Results:

[0118] There is no obvious sign of repair on the repaired oil pipe. The thickness of the brush-plated layer is 30-50μm. The porosity of the brush-plated part was tested with iron reagent and the result was 0, indicating that the coating is dense and completely covers the damaged part. Fig.10 .

[0119] A 5% NaCl solution brush corrosion test was carried out on the repaired part, and no rust was found after 96 hours, indicating good corrosion resistance.

[0120] The hardness of the coating is about 690HV. The wear resistance of the brush-plated NiWP-SiC and tungsten alloy coating samples is compared and tested using a friction and wear tester. The friction coefficient curve is shown in Fig.11 The average friction coefficients are 0.422 and 0.438 respectively, which proves that the wear resistance is similar. The corrosion resistance and wear resistance of the brush-plated repaired parts are similar to those of normal qualified products, and do not affect the service life of the oil pipe.

[0121] The above specific implementation methods further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific implementation methods of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A brush plating solution for repairing tungsten alloy electroplating layer, characterized in that: Prepared by the following method: Add sodium tungstate, sodium citrate, citric acid, nickel sulfate, and sodium hypophosphite to deionized water, heat and stir to dissolve, and adjust the pH value to 7.0-9.0 to obtain a basic solution; The SiC particles are washed with deionized water, filtered after sedimentation, and the SiC particles after sedimentation and filtration are added into the basic solution, and deionized water is added to make up the volume and stirred to obtain a brush plating solution.

2. A brush plating solution for repairing tungsten alloy electroplating layer according to claim 1, characterized in that: The plating solution contains sodium tungstate at a concentration of 20 to 60 g / L, sodium citrate at a concentration of 20 to 80 g / L, citric acid at a concentration of 20 to 50 g / L, nickel sulfate at a concentration of 10 to 60 g / L, sodium hypophosphite at a concentration of 2 to 20 g / L, and SiC particles at an added amount of 5 to 40 g / L.

3. The brush plating solution for repairing tungsten alloy electroplating layer according to claim 1, characterized in that: The plating solution contains 30-50 g / L sodium tungstate, 40-60 g / L sodium citrate, 20-40 g / L citric acid, 30-50 g / L nickel sulfate, 5-10 g / L sodium hypophosphite, and 10-30 g / L SiC particles.

4. The brush plating solution for repairing tungsten alloy electroplating layer according to claim 1, characterized in that: The particle size of the SiC particles is 0.5-5 μm, and ammonia water is used to adjust the pH value of the basic solution.

5. A brush plating process for repairing tungsten alloy electroplating layer, characterized in that: The brush plating liquid as claimed in any one of claims 1 to 4 is used for brush plating, and the brush plating layer formed after brush plating consists of the following substances: SiC: 3-15wt%, P: 3-10wt%, W: 5-25wt%, and Ni: the remainder.

6. A brush plating process for repairing tungsten alloy electroplating layer according to claim 5, characterized in that: The hardness of the brush-plated layer formed after brush plating is 650-1100 Hv.

7. A brush plating process for repairing tungsten alloy electroplating layer according to claim 5, characterized in that: The following steps are used: Heat the brush plating solution to 55-85°C; Pre-treat the parts to be repaired. The pre-treatment process includes: grinding, degreasing, activation, and cleaning; Use a brush pen to dip into the heated brush plating liquid to perform brush plating on the pre-treated repaired parts; After brush plating, rinse and blow dry.

8. A brush plating process for repairing tungsten alloy electroplating layer according to claim 7, characterized in that: During the pretreatment process, firstly, different types of sandpaper are used to grind and repair the surface defects of the part to be plated from coarse to fine, until the part to be plated and the surrounding coating are in a smooth transition state. The coarse sandpaper is used for grinding and flattening, and the fine sandpaper is used for polishing. Then use degreasing agent to clean, water to wash and dilute acid to activate; Then rinse with water and proceed with brush plating.

9. A brush plating process for repairing tungsten alloy electroplating layer according to claim 7, characterized in that: The brush plating power supply is a high-frequency switching power supply. The voltage is set to be stabilized during brush plating, the voltage is set at 4 to 15V, and the brush plating speed is 60 to 80μm / h.

10. A brush plating process for repairing tungsten alloy electroplating layer according to claim 7, characterized in that: The anode material used for brush plating is 316 stainless steel plate or iridium tantalum oxide electrode plate; The anode plate is made into a plate, semicircle or rod shape that can fit tightly to the brush-plated part of the workpiece to be repaired. A round rod of the same material is welded in the middle of the back of the anode plate as a conductive handle, and the anode is wrapped with cotton cloth. The conductive handle is connected to a copper wire to form a brush pen for brush plating.

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