Preparation method of zinc-nickel alloy coating

Abstract

The invention discloses a preparation method of a zinc-nickel alloy coating. A formula of a plating solution comprises zinc chloride, nickel sulfate hexahydrate, sodium hydroxide, sodium potassium tartrate tetrahydrate, trisodium citrate, potassium citrate, triethanolamine, tetraethylenepentamine, a primary brightener and a secondary brightener. A double-acid compound complexing agent is used for replacing a traditional single-acid complexing agent, and a plating layer can have a finer crystal structure by compounding a basic plating solution to electroplate a zinc-nickel alloy, so that the plating layer with more excellent corrosion resistance is obtained; the stability of metal ions in an electroplating solution is improved, the conductivity and uniformity of the electroplating solution are improved, the quality of a plating layer can be remarkably improved, the corrosion resistance and hardness of the plating layer are improved, pores in the plating layer are reduced, and the protection capability on a matrix is enhanced.

Description

Technical Field

[0001] The invention relates to the field of metal surface treatment, in particular to a double acid compound complexing agent electroplating process method. Background Art

[0002] Zinc-nickel alloy electroplating has better corrosion resistance and environmental protection performance than traditional electroplating, which helps to reduce the impact on the environment and also provides better product surface protection. In addition, the development of zinc-nickel alloy electroplating technology also meets the current requirements for clean production and green manufacturing, and helps to promote the sustainable development of the electroplating industry. Zn-Ni alloy coatings can be used not only for traditional corrosion mitigation, but also for other applications such as electrocatalysis. An effective method is to add complexing agents to the electroplating solution. Different complexing agents can have different effects on the coating. Some complexing agents can improve the stability of metal ions in the electroplating solution, improve the conductivity and uniformity of the electroplating solution, and thus produce a dense and uniform coating. Sometimes, in order to obtain a coating with excellent performance and maintain a suitable reaction deposition rate, multiple complexing agents are often used in combination to complement each other and achieve better comprehensive results. The electroplating solution that often uses a double acid complexing agent in the gold plating process can significantly improve the quality of the coating and obtain a dense coating structure. This fine coating structure not only improves the corrosion resistance and hardness of the coating, but also reduces the pores in the coating and enhances the protection of the substrate. In contrast, the coating surface morphology obtained by the traditional single-acid complexing agent electroplating solution is uneven and has a large number of micropores, which affects the overall performance of the coating. Therefore, the use of double acid complexing agents has significant advantages in the electroplating industry. It not only improves the performance of the coating, but also reduces the environmental risks in the production process, and promotes the electroplating industry to develop in a more environmentally friendly and efficient direction. Summary of the invention

[0003] In order to solve the above problems, the present invention provides a technical solution: a method for preparing a zinc-nickel alloy coating, characterized in that the plating solution formula includes: zinc chloride, nickel sulfate hexahydrate, sodium hydroxide, potassium sodium tartrate, trisodium citrate, potassium citrate, triethanolamine, tetraethylene pentamine, primary brightener, secondary brightener; the electroplating process parameters are as follows: temperature 23-27°C, plating solution pH: 12, cathode current density 1A / dm², activation time 30s, electroplating time 10 minutes; the compound complexing agent formula: potassium sodium tartrate 6.44g / L, trisodium citrate 20.14g / L, potassium citrate 22.21g / L, triethanolamine 10.22g / L, tetraethylene pentamine 12g / L; the plating solution preparation process is as follows: S1. Add potassium sodium tartrate, trisodium citrate, potassium citrate, triethanolamine, and tetraethylenepentamine to beaker A, and add deionized water to dissolve; S2. Dissolve nickel sulfate hexahydrate in deionized water and slowly add it to beaker A after dissolution; S3. Add sodium hydroxide to beaker B, add deionized water to dissolve, and stir until the solution is clear; S4. Dissolve zinc oxide in deionized water, stir until clear, slowly add to beaker B, and continue stirring until the solution is clear; S5. Slowly add the solution in beaker B into beaker A while stirring, and then add primary brightener and secondary brightener; stir the mixed solution evenly.

[0004] The invention uses a double acid compound complexing agent in a zinc-nickel alloy electroplating process. Compared with the conventional zinc-nickel alloy plating using a single acid complexing agent, the coating has better corrosion resistance and a longer service life of the zinc-nickel alloy. Potassium sodium tartrate in the double acid compound complexing agent helps control the growth of crystal grains when used as a complexing agent, thereby obtaining a finer crystal grain structure and improving the flatness of the coating. Meanwhile, grain refinement can make the coating denser, reduce pores and defects, and thus improve the corrosion resistance and wear resistance of the coating.

[0005] Sodium citrate, another component of the double acid complexing agent, can maintain pH stability as a complexing agent, prevent metal salt precipitation, and reduce the concentration of free metal ions, so as to obtain a coating with good bonding, low stress, and strong corrosion resistance. At the same time, sodium citrate can form a stable complex with zinc and nickel ions in the solution, which helps to maintain the uniform distribution of metal ions, thereby reducing the generation of pores. The electroplating of zinc-nickel alloy with a double acid complexing agent with a reasonable proportion improves and optimizes the flatness and corrosion resistance of the coating, reduces the porosity, and greatly promotes the development of excellent performance of zinc-nickel alloy coatings.

[0006] The invention patent "A zinc-nickel alloy electroplating process" (CN202311600677) discloses a zinc-nickel alloy electroplating process. The basic plating solution formula contains only a single acid complexing agent, while the complexing agent used in the present invention is a double acid compound complexing agent. Compared with the single acid complexing agent, the electroplated coating has better corrosion resistance, better flatness, and lower porosity; the invention patent "A zinc-nickel alloy electrochemical deposition solution, deposition layer, and preparation method thereof" (CN202211235196) proposes a method of using sodium citrate as a complexing agent to complex metal ions to form a stable complex, close the deposition rate of nickel ions and zinc ions, and promote alloy synthesis. The formula only uses sodium citrate as a complexing agent. Compared with the present invention, which uses trisodium citrate and potassium sodium tartrate to form a complexing agent, the coating of the present invention has better flatness and corrosion resistance, lower porosity, and the performance of the zinc-nickel alloy coating plated by the present invention is better.

[0007] The present invention adds a double acid complexing agent into the basic plating solution, which improves the stability of metal ions in the electroplating solution, improves the conductivity and uniformity of the electroplating solution, thereby producing a dense and uniform effect, can significantly improve the quality of the plating layer, improve the corrosion resistance and hardness of the plating layer, reduce the pores in the plating layer, and enhance the protection ability of the substrate.

[0008] The specific electroplating process is: substrate degreasing → water washing → pickling and rust removal → water washing → pickling and rust removal → water washing → activation → electroplating → water washing → blow drying and testing.

[0009] The electroplating solution formula is a zinc-nickel alloy plating solution formula: zinc chloride 10g / L, nickel sulfate hexahydrate 12g / L, sodium hydroxide 100g / L, potassium sodium tartrate 6.44g / L, trisodium citrate 20.14g / L, potassium citrate 22.21g / L, triethanolamine 10.22g / L, tetraethylenepentamine 12g / L, primary brightener 12g / L, secondary brightener 12g / L, pH 12.0, temperature 23-27°C, cathode current density 1A / dm².

[0010] Preferably, the four water washes are pure cold water washes.

[0011] The formula of the composite complexing agent used in the passivation process is: 6.44 g / L potassium sodium tartrate, 20.14 g / L trisodium citrate, 22.21 g / L potassium citrate, 10.22 g / L triethanolamine, 12 g / L tetraethylene pentamine, pH 12.0, temperature 25°C.

[0012] The preparation method of double acid complexing agent is: a. Pour the calculated amount of potassium sodium tartrate into a small amount of water and stir to fully dissolve; b. Pour the calculated amount of trisodium citrate into a small amount of water and stir to fully dissolve it; c. Pour the calculated amount of potassium citrate into a small amount of water and stir to fully dissolve it; d. Pour the calculated amount of triethanolamine into a small amount of water and stir to fully dissolve it; e. Pour the calculated amount of tetraethylenepentamine into a small amount of water and stir to fully dissolve it; f. Mix ae solution and stir to dissolve until clear.

[0013] Compared with the prior art, the present invention has the following beneficial effects: using a double acid compound complexing agent to replace the traditional single acid complexing agent, the compound basic plating solution for electroplating zinc-nickel alloy can make the coating have a finer crystal structure, thereby obtaining a coating with better corrosion resistance; improving the stability of metal ions in the electroplating solution, improving the conductivity and uniformity of the electroplating solution, which can significantly improve the quality of the coating, improve the corrosion resistance and hardness of the coating, reduce the pores in the coating, and enhance the protection ability of the substrate. DETAILED DESCRIPTION

[0014] The invention provides a technical solution: a method for preparing a zinc-nickel alloy coating, characterized in that a plating solution formula comprises: zinc chloride, nickel sulfate hexahydrate, sodium hydroxide, potassium sodium tartrate, trisodium citrate, potassium citrate, triethanolamine, tetraethylene pentamine, a primary brightener, and a secondary brightener; the electroplating process parameters are as follows: temperature 23-27°C, plating solution pH: 12, cathode current density 1A / dm², activation time 30s, and electroplating time 10 minutes; the compound complexing agent formula: potassium sodium tartrate 6.44g / L, trisodium citrate 20.14g / L, potassium citrate 22.21g / L, triethanolamine 10.22g / L, and tetraethylene pentamine 12g / L; the plating solution preparation process is as follows: S1. Add potassium sodium tartrate, trisodium citrate, potassium citrate, triethanolamine, and tetraethylenepentamine to beaker A, and add deionized water to dissolve; S2. Dissolve nickel sulfate hexahydrate in deionized water and slowly add it to beaker A after dissolution; S3. Add sodium hydroxide to beaker B, add deionized water to dissolve, and stir until the solution is clear; S4. Dissolve zinc oxide in deionized water, stir until clear, slowly add to beaker B, and continue stirring until the solution is clear; S5. Slowly add the solution in beaker B into beaker A while stirring, and then add primary brightener and secondary brightener; stir the mixed solution evenly.

[0015] Embodiment 1:

[0016] a. Use sandpaper to smooth the sample; b. Rinse the sample with deionized water; c. Add 6.44 g of sodium potassium tartrate, 20.14 g of trisodium citrate, 22.21 g of potassium citrate, 10.22 g of triethanolamine, and 12 g of tetraethylene pentamine to beaker A, and dissolve in 200 mL of deionized water; d. Dissolve 12 g of nickel sulfate hexahydrate in 50 mL of deionized water and slowly add to beaker A after dissolution; e. Add 100g of sodium hydroxide to beaker B, add 200mL of deionized water to dissolve, and stir until the solution is clear; f. Dissolve 10g zinc oxide in 100mL deionized water, stir until the solution is clear, slowly add to beaker B, and continue stirring until the solution is clear; g. Slowly add the solution in beaker B to beaker A under stirring, and then add 12mL primary brightener and 12mL secondary brightener; h. The mixed solution was fixed to 1000 mL and stirred to mix evenly; i. Take Q235 steel plate as cathode plate and perform pretreatment according to the steps of substrate degreasing → water washing → pickling and rust removal → water washing → pickling and rust removal → water washing → activation; j. The electroplating time is 10 minutes, turn on the power, and use 1A / dm² electroplating.

[0017] Comparative Example 1:

[0018] a. Add 12g of complexing agent to beaker A and dissolve it in 200mL of deionized water; then dissolve 10g of nickel sulfate in 50mL of deionized water and slowly add it to beaker A after dissolution; b. Add 100 g of sodium hydroxide to beaker B and dissolve it in 200 mL of deionized water, stirring until the solution is clear; c. Dissolve 12g zinc oxide in 100mL deionized water, stir until suspension, slowly add to beaker B, and continue stirring until the solution is clear; d. Slowly add the solution in beaker B to beaker A while stirring, and then add 8 mL of additive; e. Take Q235 steel plate as cathode plate, and perform pretreatment according to the steps of substrate degreasing → water washing → pickling and rust removal → water washing → grinding → water washing → weak etching → water washing; f. Set the pulse power supply parameters: the first set of pulse parameters is pulse width 300ms, cycle 1000ms, frequency 1000Hz, working time 15ms, total electroplating time 10 minutes, turn on the power, and use 1A / dm² electroplating; g. After electroplating, wash with water and passivate in the passivation solution for 15 seconds. After taking out, stop for 10 seconds and then wash with water twice. After drying, obtain the sample.

[0019] Comparative Example 2: a. Sequentially weigh 16 g of sodium citrate, 12 g of citric acid, 0.04 g of sodium dodecyl sulfate, 0.12 g of vanillin, 20 g of nickel sulfate and 12 g of zinc sulfate (all reagents used were analytical grade) and dissolved in 100 mL of deionized water. The pH value of the deposition solution was between 6 and 6.5. The prepared solution was stirred and ultrasonicated for later use. b. Use the solution prepared in step a as the deposition solution, the high-temperature alloy after cleaning and polishing pretreatment as the working electrode, the platinum sheet as the counter electrode, and the saturated calomel electrode as the reference electrode to form a three-electrode system, ensure that the distance between the working electrode and the platinum sheet is 2 cm, use a temperature control device to control the temperature of the deposition solution at 25°C ± 1°C, and the deposition potential is controlled at -1.15V to -1.3V (relative to the saturated calomel electrode), and apply magnetic stirring for 30 minutes to obtain a zinc-nickel alloy deposition layer.

Claims

1. A method for preparing a zinc-nickel alloy coating, characterized in that: The plating solution formula includes: zinc chloride, nickel sulfate hexahydrate, sodium hydroxide, potassium sodium tartrate, trisodium citrate, potassium citrate, triethanolamine, tetraethylene pentamine, primary brightener, secondary brightener; the electroplating process parameters are as follows: temperature 23-27°C, plating solution pH: 12, cathode current density 1A / dm², activation time 30s, electroplating time 10 minutes; the compound complexing agent formula: potassium sodium tartrate 6.44g / L, trisodium citrate 20.14g / L, potassium citrate 22.21g / L, triethanolamine 10.22g / L, tetraethylene pentamine 12g / L; the plating solution preparation process is as follows: S1. Add potassium sodium tartrate, trisodium citrate, potassium citrate, triethanolamine, and tetraethylenepentamine to beaker A, and add deionized water to dissolve; S2. Dissolve nickel sulfate hexahydrate in deionized water and slowly add it to beaker A after dissolution; S3. Add sodium hydroxide to beaker B, add deionized water to dissolve, and stir until the solution is clear; S4. Dissolve zinc oxide in deionized water, stir until clear, slowly add to beaker B, and continue stirring until the solution is clear; S5. Slowly add the solution in beaker B into beaker A while stirring, and then add primary brightener and secondary brightener; stir the mixed solution evenly.