Process method for improving brightness of amorphous Ni-P coating

Abstract

The invention discloses a process method for improving the brightness of an amorphous Ni-P coating. The process method comprises the steps of metal substrate pretreatment, plating solution preparation and chemical plating, the pretreatment of the metal substrate comprises the following steps: grinding and polishing the metal substrate, cleaning and drying to obtain a to-be-plated metal substrate; the plating solution comprises the following components: 10-50 g / L of nickel sulfate hexahydrate, 1-10 g / L of nickel acetate tetrahydrate, 20-50 g / L of trisodium citrate dihydrate, 1-20 g / L of potassium sodium tartrate tetrahydrate, 0.1-1.5 g / L of lauryl sodium sulfate, 20-60 g / L of ammonium acetate and 10-45 g / L of sodium hypophosphite, and the pH value of the plating solution is 6-7; and putting the to-be-plated metal substrate serving as a cathode and a Ni sheet serving as an anode into the plating solution, and electrifying to obtain the chemically-plated metal substrate. The chemical plating solution is simple in component, free of heavy metal ions and environmentally friendly; the surface of the plating layer is flat, compact and free of obvious air holes in the microcosmic aspect, and shows the mirror surface bright effect in the macroscopic aspect.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology, and in particular to a process method for improving the brightness of amorphous Ni-P coatings. Background Technology

[0002] In surface treatment technology, electroless plating is simpler to use than electroplating equipment, requires no power supply, and consumes less energy. Furthermore, the electroless plating coating is obtained through a self-catalytic reaction within the workpiece itself, resulting in better adhesion, more uniform coating thickness, and significantly better conformability than electroplating. Therefore, electroless plating technology is widely used in surface treatment of parts across various fields.

[0003] Ni-P layers are widely used in many fields such as chemical engineering, machinery, aerospace, and electrical electronics. However, with the development of technology, many fields not only require electroless Ni-P plating to have better functionality but also higher decorative properties. Therefore, bright Ni-P coatings have attracted great attention.

[0004] Research on bright Ni-P coatings has been reported. Xiao Xin (Optimization of Bright Electroless Nickel-Phosphorus Alloy Plating Process for Aluminum and Aluminum Alloys [J]. Materials Protection, 2011, 44(03):64-67+91.) proposed the following process: 25-35 g / L nickel sulfate hexahydrate, 25-40 g / L sodium hypophosphite, 15-25 mL / L lactic acid, 8-12 g / L sodium citrate, 15 g / L sodium acetate trihydrate, 40-50 mg / L inorganic salts (compounded from lead acetate, potassium iodate, cadmium sulfate, cerium sulfate, bismuth sulfate, copper sulfate, etc.), 10 mg / L 2-ethylhexyl sulfate, 0.4 g / L saccharin, 5-10 mg / L PPS, 5-10 mg / L DEP, pH 4.4-4.8, temperature 80-90℃. This process can obtain a high-brightness coating, but the electroless plating temperature is high and the plating solution has poor stability. Furthermore, brighteners have complex compositions and contain heavy metals such as lead and cadmium, which are detrimental to environmental protection.

[0005] CN106048568B discloses an environmentally friendly electroless nickel plating method. The method uses carbon steel, aluminum alloy, or similar materials as a substrate, and a base solution of nickel sulfate hexahydrate, sodium hypophosphite, sodium acetate trihydrate, citric acid monohydrate, and lactic acid as a base solution. Benzoimidazole is added as a stabilizer, and a mixture of potassium iodide and copper sulfate is used as a brightener. This plating solution can achieve a bright plating effect, but the brightness is not ideal. It is worth noting that this invention requires the separate preparation of solutions A, B, and C according to specific requirements, followed by tank preparation, making the process very complex. Furthermore, the main salt and brightener need to be replenished every half hour during the electroless plating process, further complicating the process.

[0006] CN110029333A discloses a high-brightness Ni-P electroless plating solution. The solution is used for electroless plating on aluminum alloys and has the following formula: nickel sulfate hexahydrate 16-80 g / L, sodium hypophosphite 20-60 g / L, complexing agent 12-48 g / L (the complexing agent is at least one of citric acid monohydrate and sodium acetate trihydrate), accelerator glycine 2-20 g / L, stabilizer thiourea 0.6-10.0 mg / L, and composite brightener 6-100 mg / L (the composite brightener contains at least two components of N,N-diethylpropynylamine, propynyl ethoxylate, or bismuth sulfate). This process can obtain a uniform, smooth, dense, and mirror-bright Ni-P coating. However, this electroless plating requires two zinc immersion treatments, making the process complex, and the operating temperature is high. The plating solution is unstable, and the surface morphology of the obtained samples has problems such as cellular protrusions and textures, resulting in an uneven surface.

[0007] Existing bright coatings suffer from problems such as complex composition, the presence of multiple heavy metals, poor stability, and uneven morphology. To address these issues, a process method for improving the brightness of amorphous Ni-P coatings is proposed. Summary of the Invention

[0008] To solve the above-mentioned technical problems, the present invention provides a Ni-P coating that is flat and dense on a microscopic scale, without cellular protrusions or pores, and exhibits a mirror-like gloss on a macroscopic scale.

[0009] According to one aspect of the present invention, a process method for improving the brightness of amorphous Ni-P coatings is provided, the process method comprising metal substrate pretreatment, plating solution preparation, and electroless plating; The metal substrate pretreatment involves grinding, polishing, cleaning, and drying the metal substrate to obtain the metal substrate to be plated. The plating solution has the following composition: nickel sulfate hexahydrate 10~50 g / L, nickel acetate tetrahydrate 1~10 g / L, trisodium citrate dihydrate 35~50 g / L, potassium sodium tartrate tetrahydrate 1~20 g / L, sodium dodecyl sulfate 0.1~1.5 g / L, ammonium acetate 20~60 g / L, sodium hypophosphite 10~45 g / L, and the pH of the plating solution is 6~7. The chemical plating process involves placing the metal substrate to be plated as the cathode and the Ni sheet as the anode in the plating solution, and then applying an electric current to perform the chemical plating to obtain the chemically plated metal substrate.

[0010] Furthermore, the metal substrate is a Cu substrate or a 20# steel substrate.

[0011] Furthermore, the composition of the plating solution is as follows: nickel sulfate hexahydrate 40~60 g / L, nickel acetate tetrahydrate 5~10 g / L, trisodium citrate dihydrate 40~50 g / L, potassium sodium tartrate tetrahydrate 10~20 g / L, sodium dodecyl sulfate 0.1~0.5 g / L, ammonium acetate 40~60 g / L, sodium hypophosphite 10~25 g / L, and the pH of the plating solution is 6.

[0012] Furthermore, the power supply voltage used for the electroless plating is 0.5~4V; The energizing time is 1~10s; The electroless plating time is 0.2~4 hours; The electroless plating temperature is 60~70℃.

[0013] Furthermore, the surface of the chemically plated metal substrate is smooth and dense, without cellular protrusions or pores.

[0014] Furthermore, the thickness of the coating on the chemically plated metal substrate is 1~80 μm, and the coating is amorphous.

[0015] Furthermore, the Ni content in the coating of the electroless metal substrate is 75~85 at.%, and the P content is 15~25 at.%.

[0016] Furthermore, the gloss of the chemically plated metal substrate is 495 Gu to 515 Gu.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The chemical plating solution used in the technical solution disclosed in this invention has a simple composition, no heavy metal ions, and is environmentally friendly.

[0018] (2) The chemical plating temperature described in the technical solution disclosed in this invention is 60-70℃, and the energy consumption is low.

[0019] (3) The technical solution disclosed in this invention has a simple process, is easy to operate, and has a good activation effect.

[0020] (4) The amorphous Ni-P coating prepared by the technical solution disclosed in this invention has a smooth and dense surface without pores due to proper control of the plating solution formula, and exhibits a mirror effect on a macroscopic scale; the brightness can reach up to 515 Gu, and the resulting bright Ni-P coating is amorphous. Attached Figure Description

[0021] Figure 1 This is a SEM image of the surface of the Ni-P sample prepared in Comparative Example 3 of this invention. Figure 2The surface morphology of the Ni-P layer prepared by SEO W et al. as described in Comparative Example 3 of this invention is shown (a. 75℃, b. 80℃, c. 85℃). Figure 3 This is a SEM image of the surface of the bright amorphous Ni-P coating prepared in Example 1 of the present invention; Figure 4 These are macroscopic morphology images of the bright amorphous Ni-P coatings prepared in Examples 1-2 of this invention. Figure 5 The XRD pattern of the bright amorphous Ni-P coating prepared in Example 1 of this invention; Figure 6 This is a SEM image of the Ni-P coating prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0023] Unless otherwise specified, the reagents and substrates used in the embodiments and comparative examples of this invention were all obtained through purchase.

[0024] Example 1 Step 1, Pretreatment: Grind and polish the metal substrate (Cu plate), and ultrasonically clean it to obtain the Cu substrate to be plated; Step 2, Plating solution preparation: Nickel sulfate hexahydrate 40 g / L, nickel acetate tetrahydrate 10 g / L, trisodium citrate dihydrate 50 g / L, potassium sodium tartrate tetrahydrate 10 g / L, sodium dodecyl sulfate 0.1 g / L, ammonium acetate 40 g / L, sodium hypophosphite 25 g / L, adjust pH to 6; Step 3, chemical plating: The plating solution described in Step 2 is placed in a constant temperature heater, and the temperature is controlled at 60℃. The Cu substrate to be plated obtained in Step 1 is used as the cathode, and the Ni sheet is used as the anode. It is placed in the plating solution, and the power supply voltage is set to 0.5V to activate for 1 second. The chemical plating continues for 0.5 h to obtain a chemically plated Cu substrate. The surface of the substrate has a Ni-P amorphous coating. The composition of the coating is Ni 79 at.%, P 21 at.%, and the coating thickness is 4.2 μm. The surface morphology of the coating is as follows. Figure 3 (Scanning electron microscopy characterization image) and Figure 4 As shown in the macroscopic image, the brightness of the Cu substrate with the coating is 495 Gu.

[0025] Comparative Example 1 The difference from Example 1 is that in step 2, the plating solution uses 30 g / L of trisodium citrate dihydrate. Trisodium citrate dihydrate is a complexing agent. With less complexing agent in the plating solution, there are more free main salt ions and reducing agents during the electroless plating reaction, resulting in a more vigorous reaction. Therefore, the surface of the electroless Ni-P plating layer is uneven and shows textures, such as... Figure 6 As shown.

[0026] Comparative Example 2 The difference from Example 1 is that the plating solution in step 2 uses 40 g / L sodium hypophosphite. Sodium hypophosphite is a reducing agent; a high concentration of reducing agent in the plating solution leads to a vigorous electroless plating reaction, resulting in numerous protrusions and textures on the surface of the electroless Ni-P plating layer.

[0027] Example 2 The difference from Example 1 is that the metal substrate mentioned in steps 1 and 3 is a 20# steel substrate, while the remaining steps are consistent with Example 1, resulting in a 20# steel substrate after chemical plating. The macroscopic morphology of the plating layer is shown in the figure below. Figure 4 As shown, the results indicate that the coating has a gloss level of 515 Gu on the steel substrate.

[0028] Comparative Example 3 CN 110029333 A discloses a high-brightness Ni-P electroless plating solution. The solution formulation is as follows: nickel sulfate hexahydrate 16-80 g / L, sodium hypophosphite 20-60 g / L, complexing agent 12-48 g / L (the complexing agent is at least one of citric acid monohydrate and sodium acetate trihydrate), accelerator glycine 2-20 g / L, stabilizer thiourea 0.6-10.0 mg / L, and composite brightener 6-100 mg / L (the composite brightener contains at least two of N,N-diethylpropynylamine, propynyl ethoxylate, or bismuth sulfate). This process can obtain a uniform, smooth, dense, and mirror-bright Ni-P coating. However, this electroless plating requires two zinc immersion treatments, making the process complex, requiring high operating temperatures, and the plating solution is unstable. The resulting coating still exhibits cellular protrusions and textures (such as...). Figure 1 As shown), it is not smooth enough; in previous published research results (Seo W et al.'s "Effect of Ni-P plating temperature on growth of interfacial intermetallic compound in electrolessnickel immersion gold / Sn-Ag-Cu solder joints"), the microstructure of Ni-P coatings mostly exhibits a cellular structure (such as... Figure 2 As shown, the surface morphology of the chemically plated Ni-P layer at different temperatures is (a) 75℃, (b) 80℃ and (c) 85℃.

[0029] Comparative Example 4 CN 106048568 B discloses an environmentally friendly electroless nickel plating method. The method uses carbon steel, aluminum alloy, or other materials as a substrate, and a base solution of nickel sulfate hexahydrate, sodium hypophosphite, sodium acetate trihydrate, citric acid monohydrate, and lactic acid as a base solution. Benzoimidazole is added as a stabilizer, and a mixture of potassium iodide and copper sulfate is added as a brightener. Bright plating can be achieved using this solution, but the brightness is unsatisfactory, with a gloss level of 208 Gs (208 Gu). The electroless plating solution requires the separate preparation of solutions A, B, and C according to requirements, and then the tank preparation is carried out accordingly, making the process very complex. Furthermore, the main salt and brightener need to be replenished every half hour during the electroless plating process, further complicating the electroless plating process.

[0030] The above description is merely a few embodiments of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any modifications or alterations made by those skilled in the art without departing from the scope of the technical solution of the present invention using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A process for improving the brightness of amorphous Ni-P coatings, characterized in that, The process includes metal substrate pretreatment, plating solution preparation, and chemical plating. The metal substrate pretreatment involves grinding, polishing, cleaning, and drying the metal substrate to obtain the metal substrate to be plated. The plating solution has the following composition: nickel sulfate hexahydrate 10~50 g / L, nickel acetate tetrahydrate 1~10 g / L, trisodium citrate dihydrate 35~50 g / L, potassium sodium tartrate tetrahydrate 1~20 g / L, sodium dodecyl sulfate 0.1~1.5 g / L, ammonium acetate 20~60 g / L, sodium hypophosphite 10~45 g / L, and the pH of the plating solution is 6~7. The chemical plating process involves placing the metal substrate to be plated as the cathode and the Ni sheet as the anode in the plating solution, and then applying an electric current to perform the chemical plating to obtain the chemically plated metal substrate.

2. The process method according to claim 1, characterized in that, The metal substrate is a Cu substrate or a 20# steel substrate.

3. The process method according to claim 1, characterized in that, The plating solution has the following composition: nickel sulfate hexahydrate 40~60 g / L, nickel acetate tetrahydrate 5~10 g / L, trisodium citrate dihydrate 40~50 g / L, potassium sodium tartrate tetrahydrate 10~20 g / L, sodium dodecyl sulfate 0.1~0.5 g / L, ammonium acetate 40~60 g / L, sodium hypophosphite 10~25 g / L, and the pH of the plating solution is 6.

4. The process method according to claim 1, characterized in that, The power supply voltage used for the electroless plating is 0.5~4V; The energizing time is 1~10s; The electroless plating time is 0.2~4 hours; The electroless plating temperature is 60~70℃.

5. The process method according to claim 1, characterized in that, The surface of the chemically plated metal substrate is smooth and dense, without cellular protrusions or pores.

6. The process method according to claim 1, characterized in that, The thickness of the coating on the chemically plated metal substrate is 1~80 μm, and the coating is amorphous.

7. The process method according to claim 1, characterized in that, The coating of the electroless metal substrate has a Ni content of 75-85 at.% and a P content of 15-25 at.%.

8. The process method according to claim 1, characterized in that, The gloss of the chemically plated metal substrate is 495~515 Gu.

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