A nickel-tungsten alloy electrodeposition solution and a nickel-tungsten alloy electrodeposition method

Abstract

The present invention provides a nickel-tungsten alloy electrodeposition solution and an electrodeposition process. The nickel-tungsten alloy electrodeposition solution is prepared by dissolving nickel sulfate, sodium tungstate, sodium pyrophosphate, a brightener, and a stabilizer in deionized water. The nickel-tungsten alloy electrodeposition solution has excellent corrosion resistance and wear resistance, and the service life of the electrodeposition solution is long, the production cost is reduced, and the electrodeposited nickel-tungsten alloy coating is bright and dense.

Description

Technical Field

[0001] The invention belongs to the technical field of surface engineering, and in particular relates to a nickel-tungsten alloy electrodeposition solution and a nickel-tungsten alloy electrodeposition method. Background Art

[0002] The research on electrodeposition of tungsten and iron group elements can be traced back to 1948 when Lietzke et al. (MHLietzke, MLHolt, CODEPOSITION OF TUNGSTEN AND IRON FROM AN AQUEOUS AMMONIACAL CITRATEBATH, Journal of the Electrochemical Society, 94 (1948) 252-261) proposed a method for preparing tungsten and iron alloys by electrodeposition in a citric acid-ammonia solution. Currently, most literature reports that nickel-tungsten alloys are prepared from citric acid-ammonia aqueous solutions and optimized. Allahyarzadeh et al. have made a good summary of this (MH Allahyarzadeh, M. Aliofkhazraei, ARRezvanian, V. Torabinejad, ARS Rouhaghdam, Ni-W electrodeposited coatings: Characterization, properties and applications, Surface & Coatings Technology, 307 (2016) 978-1010). Nickel-tungsten alloy electrodeposition is generally considered to be an alternative technology to hexavalent chromium electroplating. However, it is found in the production process that with the increase of use time, the coating will have problems such as pinholes and reduced hardness, which will cause the plating solution to be scrapped or need to be regenerated. The reason is that it is caused by the electrolysis products of organic matter. The life of the plating solution is generally less than 500 ampere hours / liter (or 500Ah / L), resulting in high production costs and limited application and promotion.

[0003] Pyrophosphoric acid is an inorganic complexing agent, and its decomposition product is phosphate, which has no effect on the electroplating process and is a long-life nickel-tungsten alloy electrodeposition system. Krasikov studied the structure of the nickel-tungsten alloy obtained in the pyrophosphoric acid system. The solution included nickel sulfate, sodium tungstate, potassium pyrophosphate and ammonium sulfate, but did not contain additives. The tungsten content in the coating was 31.3-32.2wt% (AVKrasikov, VLKrasikov, MAMarkov, Structural Features of Ni-W Alloy Deposited from Pyrophosphate Electrolyte, Russian Journal of Applied Chemistry, 93 (2020) 1688-1695.). Changwei Su et al. also studied the electrodeposition of nickel-tungsten alloy in the pyrophosphoric acid system. Additives were used in their system, but their composition was not disclosed.

[0004] Additives are a key component in the electrodeposition process formula. Excellent additives can improve the performance of the coating without affecting the stability of the solution. Ensorn OMI has disclosed a sulfur-containing additive that can improve the ductility of nickel-tungsten alloy coatings (application number CN99804415.6). It is mainly a type of sulfonamide compound, but the coating is not bright enough.

[0005] Therefore, it is an urgent problem to obtain a nickel-tungsten alloy electrodeposition solution with bright coating after electroplating, long service life, low production cost and stable quality. Summary of the invention

[0006] In order to solve the above problems, the purpose of the present invention is to provide a nickel-tungsten alloy electrodeposition solution, which has a long service life, a bright electrodeposition coating, stable quality and low production cost.

[0007] Another object of the present invention is to provide a nickel-tungsten alloy electrodeposition method.

[0008] In order to achieve the above-mentioned purpose, the present invention provides a nickel-tungsten alloy electrodeposition solution, which consists of nickel sulfate, sodium tungstate, sodium pyrophosphate, a brightener and a stabilizer; wherein the molar concentration of nickel sulfate is 0.02-0.2 mol / L, the molar concentration of sodium tungstate is 1-2 times that of nickel sulfate, the molar concentration of sodium pyrophosphate is 1.5-2.5 times that of nickel sulfate, the concentration of 1,4-butynediol is 0.010-0.200 g / L, the concentration of inositol is 0.005-0.100 g / L, and the pH value of the solution is 7.5-9.5.

[0009] The present invention also provides a nickel-tungsten alloy electrodeposition method, wherein the nickel-tungsten alloy electrodeposition solution is heated to 40-65°C and kept warm, stainless steel is used as an anode, and a DC power supply is used to adjust the current density of the cathode workpiece to 1-10A / dm 2 Electrodeposition was performed.

[0010] Since different workpieces have different requirements for the thickness of the electrodeposited nickel-tungsten alloy in different application scenarios, the electrodeposition time is determined according to the specific situation.

[0011] The nickel-tungsten alloy electrodeposition solution provided by the present invention utilizes an inorganic complexing agent instead of an organic acid complexing agent to perform nickel-tungsten alloy electrodeposition, thereby avoiding the problem of adverse effects of organic matter decomposition on the coating, and further solving the problem of short service life of the nickel-tungsten alloy electrodeposition plating solution; 1,4-butynediol and inositol are added to the plating solution, thereby solving the problems of cracks and slow deposition speed of the nickel-tungsten alloy electrodeposition coating in a pyrophosphate system, and the two are used in combination to obtain a nickel-tungsten alloy coating with bright appearance, high plating speed and stable quality.

[0012] The beneficial effects of the present invention are:

[0013] The invention provides a nickel-tungsten alloy electroplating solution and a nickel-tungsten alloy electroplating method. The electroplated coating obtained by electroplating the nickel-tungsten alloy electroplating solution is bright, dense and crack-free, and has a fast deposition speed. The current efficiency is 35-70%, which is much higher than the current efficiency of 15% of the existing electroplating chromium. After a long-term electroplating experiment is carried out for 3000h under the condition of 1A current in 1000mL of the nickel-tungsten alloy electroplating solution, the quality of the coating is stable and does not change, indicating that the plating solution is stable and does not decompose. The life of the plating solution is above 3000Ah / L, and the plating solution is suitable for large-scale application. The plating solution temperature is 40-65°C, which is lower than 60-80°C of a citric acid system. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The electron microscope picture of the nickel-tungsten alloy after the nickel-tungsten alloy electrodeposition solution provided by the present invention is used for electrodeposition.

[0015] Figure 2 The graph is a curve showing the change in hardness of the nickel-tungsten alloy with temperature after the nickel-tungsten alloy electrodeposition solution provided by the present invention is used for electrodeposition.

[0016] Figure 3 The figure is an XRD curve of the nickel-tungsten alloy after electrodeposition using the nickel-tungsten alloy electrodeposition solution provided by the present invention.

[0017] Figure 4 This is a SEM image (1000×) of a nickel-tungsten alloy coating obtained after using the nickel-tungsten alloy electrodeposition solution provided by the present invention at 3000 Ah / L. DETAILED DESCRIPTION

[0018] The embodiments of the present invention will be described in detail and comprehensively below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0019] The raw materials used in the following examples are all commercially available products.

[0020] Example 1

[0021] Preparation of electrodeposition solution: Add 0.2 mol sodium pyrophosphate, 0.15 mol sodium tungstate, and 0.1 mol nickel sulfate into 800 mL of deionized water and stir to dissolve. Adjust the pH of the solution to 8.0 with ammonia water, then add 0.05 g / L 1,4-butynediol and 0.02 g / L inositol and adjust the volume to 1000 mL.

[0022] Heat the prepared electrodeposition solution to 55°C and keep it warm. Use stainless steel as the inert anode and the workpiece to be electrodeposited as the cathode. The workpiece is a 30*60cm rectangular iron sheet. Control the system current density to 3A / dm 2 After 2 hours, a nickel alloy coating was obtained. The coating thickness was measured by a micrometer to be 24 μm. The deposition rate under this condition was calculated to be 12 μm / h. The nickel alloy coating had a bright appearance and a silvery-white metallic luster.

[0023] The microstructure of the coating was observed using a FEI Navo450 field emission electron microscope (EM). Figure 1 As shown, from Figure 1 It can be seen that the coating surface is flat and has no cracks. The coating composition is measured by the energy dispersive spectrometer of the electron microscope, and the nickel content is 52.9wt% and the tungsten content is 34.6wt%.

[0024] The coating was heat treated at temperatures of 200, 300, 400, 500, 600, and 700°C. The hardness of the coating after heat treatment was measured. The results are as follows: Figure 2 As shown in the figure, the vertical axis Microhardness is the microhardness, the horizontal axis T is the temperature, and the Annealed Time is the annealing time. Figure 2 It can be seen that the hardness of nickel-tungsten alloy can be increased from 510HV in the plated state to 1100HV (400℃). The increase in hardness indicates that nickel-tungsten alloy has better wear resistance. The crystal structure analysis was performed using XRD. The results are as follows: Figure 3 As shown in FIG. 1 , wherein the ordinate Intensity represents the intensity and the abscissa 2θ represents the diffraction angle. Figure 3It can be seen that below 300°C, the nickel-tungsten alloy only presents a wide and short diffraction peak near 2θ=44.5°, indicating an amorphous structure. As the temperature increases, the diffraction peak becomes stronger and narrower, and the nickel-tungsten alloy undergoes crystallization. The transformation from amorphous to nanocrystalline is the reason for the increase in hardness.

[0025] The plating solution was continued to be used, and the amount of additional addition was calculated according to the composition and weight of the coating, as well as the analysis data of the plating solution. After continuous use of 3000Ah / L, the coating was tested and the surface was bright, with a deposition rate of 11μm / h. The microscopic morphology of the coating was observed under a scanning electron microscope at 1000 times magnification, and the results were as follows: Figure 4 As shown. Figure 4 It can be seen that the coating surface is smooth and has no cracks. The energy spectrum shows that the nickel content in the coating is 61.3wt% and the tungsten content is 30.5wt%, indicating that the coating quality and composition are relatively stable.

[0026] Example 2

[0027] On the basis of Example 1, the amount of nickel sulfate was changed to 0.01 or 0.2 mol, the amount of sodium pyrophosphate was twice that of nickel sulfate, the concentration of sodium tungstate remained unchanged, and the electrodeposition process remained unchanged. Bright nickel-tungsten alloy was also obtained, but its deposition rate changed, 4 μm / h in a solution of 0.01 mol nickel sulfate and 13 μm / h in a solution of 0.2 mol nickel sulfate. It can be seen that when the concentration of nickel sulfate becomes less than 0.1 mol / L, the deposition rate changes significantly; when the concentration of nickel sulfate becomes greater than 0.1 mol / L, the deposition rate tends to be stable.

[0028] This is because the deposition rate in electroplating is generally controlled by concentration polarization and electrochemical polarization. When the main salt concentration is very low, deposition is limited by concentration polarization. Increasing the concentration can significantly increase the deposition rate. However, when the main salt concentration rises to a certain level, the influence of electrochemical polarization dominates, and continuing to increase the concentration has limited effect on the deposition rate.

[0029] Example 3

[0030] Based on Example 1, only the amount of sodium tungstate was changed to 0.1 mol or 0.2 mol, and other conditions remained unchanged, and bright nickel-tungsten alloy was also obtained, and the deposition rate was 12 μm / h, indicating that the concentration of sodium tungstate has no effect on brightness and deposition rate.

[0031] Example 4

[0032] Based on the bath composition and electrodeposition process conditions of Example 3, the electrodeposition current density was changed to 7 A / dm 2After 2 hours of electrodeposition, a bright nickel-tungsten alloy coating was obtained. The coating thickness was measured by a micrometer to be 32 μm, and the deposition rate under this condition was calculated to be 16 μm / h. This shows that increasing the current density will not have an adverse effect on the coating appearance, but can increase the electrodeposition rate.

[0033] However, since the higher the current density, the higher the energy consumption, and too high current density will cause defects such as rough and white coating, the higher the better is not necessarily true. The current density range used in the present invention is the current density range that the process can adapt to.

[0034] Example 5

[0035] Based on the bath components and electrodeposition process conditions of Example 4, the process pH value was changed to 9.0. After 2 hours of electrodeposition, a bright nickel-tungsten alloy coating was obtained. The coating thickness was measured by a micrometer to be 37 μm, and the deposition rate under this condition was calculated to be 18.5 μm / h. It shows that increasing the process pH value will not have an adverse effect on the appearance of the coating, and increasing the pH has an improving effect on the plating speed. However, from the perspective of process implementation, the pH value should not be too high. Too high ammonia volatilization in the plating solution will cause serious volatilization, affecting the working environment. In addition, when pH>9.5, the brittleness of the coating increases, affecting the performance of the coating.

[0036] Example 6

[0037] Based on the plating solution composition and electrodeposition process conditions of Example 3, the process temperature was changed to 65°C. After 2 hours of electrodeposition, a bright nickel-tungsten alloy coating was obtained. The coating thickness was measured by a micrometer to be 25 μm, and the deposition rate under this condition was calculated to be 12.5 μm / h. This shows that within a certain temperature range, the process temperature has no significant effect on the apparent generation and deposition rate of the coating.

[0038] It can be seen from the above embodiments that the present invention provides a nickel-tungsten alloy electrodeposition solution, in which the brightener 1,4-butynediol is added to make the nickel plating bright, but the nickel-tungsten alloy coating obtained in the inorganic complexing agent system has cracks and the deposition rate is significantly reduced. After introducing inositol as a stabilizer, the above shortcomings can be changed. After long-term use at 3000Ah / L, the coating quality is stable, the life of the plating solution is significantly extended, and it has broad application prospects.

[0039] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A nickel-tungsten alloy electrodeposition solution, characterized in that: The invention is prepared by dissolving nickel sulfate, sodium tungstate, sodium pyrophosphate, a brightener and a stabilizer in deionized water; wherein the molar concentration of nickel sulfate is 0.02-0.2 mol / L, the molar concentration of sodium tungstate is 1-2 times that of nickel sulfate, the molar concentration of sodium pyrophosphate is 1.5-2.5 times that of nickel sulfate, the brightener is 1,4-butynediol, the concentration of 1,4-butynediol is 0.010-0.200 g / L, the stabilizer is inositol, the concentration of inositol is 0.005-0.100 g / L, and the pH value of the solution is 7.5-9.

5.

2. The method for preparing a nickel-tungsten alloy electrodeposition solution according to claim 1, characterized in that: The method comprises the following steps: adding sodium pyrophosphate, sodium tungstate and nickel sulfate into deionized water, stirring and dissolving; adjusting the pH value of the solution to 7.5-9.5 with ammonia water, adding 1,4-butynediol and inositol, and then fixing the volume with deionized water.

3. A nickel-tungsten alloy electrodeposition method, characterized in that: The nickel-tungsten alloy electrodeposition solution as claimed in claim 1 is heated to 40-65°C and kept warm, stainless steel is used as the anode, the workpiece to be electrodeposited is used as the cathode, and the current density of the DC power supply is 1-10A / dm 2 Electrodeposition was performed.

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