Nickel plating method based on eutectic solvent

Abstract

The invention relates to the technical field of metal electroplating, in particular to a nickel plating method based on a deep-eutectic solvent, which comprises the following steps: firstly, pretreating a metal workpiece, then immersing the metal workpiece into a special electrolyte which takes a choline chloride and ethylene glycol deep-eutectic solvent as a substrate and contains nickel salt and an additive, and electroplating under the protection of inert atmosphere, and finally obtaining a nickel-plated product. According to the invention, a traditional aqueous solution system is completely abandoned, and the problems of replacement reaction and hydrogen embrittlement during active metal electroplating are fundamentally solved. The technology is low in cost, environmentally friendly, safe and easy and convenient to operate, the ultrahigh binding force of the plating layer and the base body is achieved on active metal base bodies such as magnesium alloy and titanium alloy, and a new technical scheme is provided for surface protection and functionalization of key components in the fields of IC semiconductors, new energy automobiles and the like.

Description

Technical Field

[0001] This invention relates to the field of metal electroplating technology, and more specifically to a nickel plating method based on a eutectic solvent. Background Technology

[0002] Nickel plating is widely used due to its excellent corrosion resistance, wear resistance, and decorative properties. However, traditional aqueous electroplating faces significant challenges for reactive metals such as magnesium, aluminum, and titanium, and their alloys. Because these metals have very negative standard electrode potentials, a violent displacement reaction occurs immediately upon immersion in the aqueous plating solution, generating a loose, poorly bonded displacement layer that leads to subsequent peeling and flaking of the plating. Furthermore, aqueous electroplating inevitably involves hydrogen evolution, which can cause hydrogen embrittlement and damage materials such as high-strength steel.

[0003] However, ionic liquid electroplating technology is still in the laboratory stage, and the following bottlenecks exist before it can be applied industrially: (1) High cost: Many high-performance ionic liquids are difficult to synthesize and expensive; (2) Immature process: The stability of the plating solution, the solubility of metal ions, and the electroplating process parameters (temperature, current density) lack systematic research, making it difficult to obtain a plating layer with stable quality; (3) Difficulty in controlling coating performance: The additive system that is mature in aqueous solution may fail in ionic liquid. How to effectively control the internal stress, brightness and crystal morphology of the coating is a major problem.

[0004] Therefore, developing an ionic liquid nickel plating method that is relatively low-cost, has stable processes, and can produce high-quality coatings is of great significance for expanding the application boundaries of nickel plating technology. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a nickel plating method based on a eutectic solvent.

[0006] The specific technical solution is as follows: A nickel plating method based on a eutectic solvent involves first pretreating the workpiece, then electroplating with the eutectic solvent, followed by post-treatment. The method specifically includes the following steps: (1) Workpiece pretreatment: First, mechanical grinding is used to grind the surface of the workpiece to remove the oxide scale. Then, ultrasonic cleaning is performed to remove the oil. Next, depending on the material of the workpiece, a suitable weak acid solution is selected for short-term acid pickling and activation, and then the workpiece is quickly transferred. (2) Eutectic solvent electroplating: The pretreated workpiece is used as the cathode, and the high-purity nickel plate is used as the anode. The workpiece is immersed in a special electrolyte. High-purity nitrogen or argon is introduced above the electrolytic cell to remove oxygen and moisture. At a certain temperature, a certain cathode current density is applied, and electroplating is performed for a period of time. (3) Post-treatment: After electroplating, the workpiece is taken out, cooled to room temperature in an inert atmosphere, the workpiece surface is cleaned, and then dried.

[0007] The ultrasonic cleaning and degreasing process described in step (1) uses acetone or ethanol.

[0008] The electroplating conditions described in step (2) are: applying a cathode current density of 0.5-3.0 A / dm² at a temperature of 60-90°C for 30-120 minutes.

[0009] In step (3), anhydrous ethanol or deionized water is used to clean the surface of the workpiece.

[0010] Step (3) may be followed by step (4) heat treatment: heat treatment of nickel-plated workpiece at 200-400℃ for 30-120 minutes, followed by furnace cooling to eliminate internal stress and improve the adhesion between the plating and the substrate.

[0011] The eutectic solvent electrolyte used for nickel plating is composed of the following components: Eutectic solvent base: formed by heating a mixture of choline chloride and ethylene glycol in a molar ratio of 1:2; Main salt: nickel chloride hexahydrate (NiCl2·6H2O) 0.2-0.6 mol / L; Additive: glycerol 10-30 mL / L; Stress reliever: sodium saccharin 1-5 g / L.

[0012] Compared with the prior art, the present invention has the following beneficial technical effects: This invention overcomes the shortcomings of existing aqueous electroplating technologies and expensive ionic liquids, providing a low-cost, high-adhesion nickel plating method based on a eutectic solvent with no risk of hydrogen embrittlement. The solvent of this invention is a type of organic solvent composed entirely of ions, which is liquid at or near room temperature and possesses unique properties such as high thermal stability, extremely low vapor pressure, and a wide electrochemical window (typically >3V). Electroplating in an ionic liquid fundamentally avoids the intervention of water, thereby eliminating displacement reactions and hydrogen embrittlement, and making electroplating of active metals possible. Many conventional ionic liquids (such as imidazoles) are complex to synthesize, difficult to purify, and expensive, limiting their large-scale industrial application. Eutectic solvents, as a low-cost ionic liquid-like system composed of hydrogen bond donors and acceptors, with readily available raw materials and good biodegradability, are an ideal alternative to traditional ionic liquids.

[0013] The specific advantages of this invention are as follows: (1) Extremely low cost: The low eutectic solvent is prepared by using readily available and inexpensive raw materials such as choline chloride and ethylene glycol. The overall cost is far lower than that of traditional imidazole plasma liquids, and it has the potential for large-scale industrial application. (2) Environmental protection and safety: The eutectic solvent has good biodegradability, its toxicity is much lower than that of cyanide and many organic solvents, its vapor pressure is low, and the production process is environmentally friendly; (3) Breakthrough substrate applicability: It inherits the advantages of non-aqueous electroplating and can successfully obtain nickel plating with high adhesion on active metals such as magnesium, aluminum and titanium, without the risk of hydrogen embrittlement. (4) Wide process window and easy operation: The electrolyte is easy to prepare and has good stability. The required electroplating temperature is relatively low (compared with high-temperature ionic liquids), reducing energy consumption and operation difficulty; (5) Excellent coating quality: By optimizing the formula and process, a nickel coating with fine crystals, uniformity and low internal stress can be obtained. Attached Figure Description

[0014] Figure 1 This is a process flow diagram of the nickel plating method based on a eutectic solvent according to the present invention. Detailed Implementation

[0015] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings, but the scope of protection of the present invention is not limited to the specific embodiments and accompanying drawings. Example 1

[0016] Figure 1 The figure shows a process flow diagram of the nickel plating method based on a eutectic solvent according to the present invention. Taking a magnesium alloy workpiece as an example, the workpiece is first pretreated, then electroplated using a eutectic solvent, and then post-treated. The specific steps include the following: (1) Workpiece pretreatment: First, mechanical grinding is used to grind the surface of the workpiece to remove the oxide scale. Then, ultrasonic cleaning with acetone for 10 minutes is used to remove oil. The workpiece is then activated by immersion in an ethanol solution containing 5% citric acid for 30 seconds and then quickly transferred. (2) Eutectic solvent electroplating: First, a special electrolyte is prepared, consisting of the following components: a eutectic solvent base: choline chloride and ethylene glycol are mixed in a molar ratio of 1:2 and heated and stirred until a homogeneous and transparent liquid is formed; then, the main salt: nickel chloride hexahydrate (NiCl2·6H2O) 0.2mol / L, the additive: glycerol 10mL / L, and the stress reliever: sodium saccharin 1g / L are added; then, the pretreated workpiece is used as the cathode, and the high-purity nickel plate is used as the anode, and the workpiece is immersed in the special electrolyte. High-purity nitrogen is introduced above the electrolytic cell to remove oxygen and moisture. At a temperature of 60℃, a cathode current density of 0.5A / dm² is applied, and electroplating is performed for 30 minutes. (3) Post-treatment: After electroplating, the workpiece is taken out, cooled to room temperature under an inert atmosphere, cleaned with anhydrous ethanol, and then dried. (4) Optional heat treatment: The nickel-plated workpiece is heat-treated at 200°C for 30 minutes, followed by furnace cooling. This eliminates internal stress and improves the adhesion between the plating and the substrate. Example 2

[0017] The difference from Example 1 is that in step (1), ultrasonic cleaning and degreasing are performed using ethanol, and the acid pickling activation time is 10 seconds. The electroplating conditions in step (2) are: argon gas is introduced above the electrolytic cell, and a cathode current density of 2.0 A / dm² is applied at a temperature of 80°C for 100 minutes. The special electrolyte is composed of the following components: eutectic solvent base: choline chloride and ethylene glycol are mixed and heated in a molar ratio of 1:2; main salt: nickel chloride hexahydrate (NiCl2·6H2O) 0.4 mol / L; additive: glycerol 20 mL / L; stress reliever: sodium saccharin 3 g / L; in step (3), the surface of the workpiece is cleaned with deionized water; in step (4), the nickel-plated workpiece is heat-treated at 400°C for 120 minutes to eliminate internal stress and improve the adhesion between the plating layer and the substrate. Example 3

[0018] The difference from Example 1 is that the electroplating conditions in step (2) are: applying a cathode current density of 3.0 A / dm² at a temperature of 90°C for 120 minutes; the special electrolyte consists of the following components: eutectic solvent base: choline chloride and ethylene glycol mixed in a molar ratio of 1:2 and heated; main salt: nickel chloride hexahydrate (NiCl2·6H2O) 0.6 mol / L; additive: glycerol 30 mL / L; stress reliever: sodium saccharin 5 g / L. Furthermore, the heat treatment in step (4) is not performed.

Claims

1. A nickel plating method based on a eutectic solvent, characterized in that, First, the workpiece undergoes pretreatment, followed by electroplating with a eutectic solvent, and then post-treatment, specifically including the following steps: (1) Workpiece pretreatment: First, mechanical grinding is used to grind the surface of the workpiece to remove the oxide scale. Then, ultrasonic cleaning is performed to remove the oil. Next, depending on the material of the workpiece, a suitable weak acid solution is selected for short-term acid pickling and activation, and then the workpiece is quickly transferred. (2) Eutectic solvent electroplating: The pretreated workpiece is used as the cathode, and the high-purity nickel plate is used as the anode. The workpiece is immersed in a special electrolyte. High-purity nitrogen or argon is introduced above the electrolytic cell to remove oxygen and moisture. At a certain temperature, a certain cathode current density is applied, and electroplating is performed for a period of time. (3) Post-treatment: After electroplating, the workpiece is taken out, cooled to room temperature in an inert atmosphere, the workpiece surface is cleaned, and then dried.

2. The nickel plating method based on a eutectic solvent according to claim 1, characterized in that: The ultrasonic cleaning and degreasing process described in step (1) uses acetone or ethanol.

3. The nickel plating method based on a eutectic solvent according to claim 1, characterized in that: The electroplating conditions described in step (2) are: applying a cathode current density of 0.5-3.0 A / dm² at a temperature of 60-90°C for 30-120 minutes.

4. The nickel plating method based on a eutectic solvent according to claim 1, characterized in that: In step (3), anhydrous ethanol or deionized water is used to clean the surface of the workpiece.

5. The nickel plating method based on a eutectic solvent according to claim 1, characterized in that: Step (3) may be followed by step (4) heat treatment: heat treatment of nickel-plated workpiece at 200-400℃ for 30-120 minutes, followed by furnace cooling to eliminate internal stress and improve the adhesion between the plating and the substrate.

6. The nickel plating method based on a eutectic solvent according to claim 1, characterized in that: The eutectic solvent electrolyte used for nickel plating is composed of the following components: Eutectic solvent base: formed by heating a mixture of choline chloride and ethylene glycol in a molar ratio of 1:2; Main salt: nickel chloride hexahydrate (NiCl2·6H2O) 0.2-0.6 mol / L; Additive: glycerol 10-30 mL / L; Stress reliever: sodium saccharin 1-5 g / L.

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