A process for plating thick nickel with no burr and high phosphorus

Abstract

The present application relates to a kind of processes for thickening nickel plating of high phosphorus without burr, specifically comprising metal substrate pretreatment, plating solution preparation, plating solution post-treatment and electroless nickel plating steps. The plating solution composed of sodium phosphate dibasic, nickel sulfate, sodium hypophosphite, sodium fluoride, sodium citrate, propionic acid, bismuth nitrate, chelidamic acid, copper sulfate and sodium dodecyl sulfate is used for electroless nickel plating after compounding with composite stabilizer C. Composite stabilizer C is compounded by stabilizer A and stabilizer B according to a volume ratio of 2:1, wherein stabilizer A is composed of sodium thiosulfate and potassium iodate, and stabilizer B is composed of sodium dodecyl sulfate and ammonium molybdate. The present application overcomes the generation of burr while ensuring the thickening of the coating, and the coating is uniform, low cost, environmentally friendly and durable. The utilization rate of nickel in the plating solution is high, and the service life of the plated part is long.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of high phosphorus thick nickel plating process without burr, specifically belongs to metal surface processing technical field. BACKGROUND

[0002] Low-phosphorus electroless nickel plating process was used in the early application of electroless nickel plating, but the obtained coating is rough, poor adhesion, and the bath stability is poor, easy to decompose and fail, and the life cycle is short. The phosphorus content in the coating of the electroless nickel-phosphorus alloy widely used in industry from the late 1970s to the 1980s is about 8wt%, which is called medium-phosphorus coating. Because it cannot be compared with electroplating, it has been rapidly developed in industrial production. With the progress of science and technology, the medium-phosphorus electroless nickel coating cannot meet the requirements of corrosion resistance under harsh conditions, and the electroless nickel technology begins to develop towards high-phosphorus coating. High-phosphorus electroless nickel coating has amorphous structure, which not only has excellent corrosion resistance and wear resistance, but also has stable non-magnetic, high resistivity, low temperature coefficient and heat resistance, etc. It is a kind of excellent functional coating, widely used in computer hard disk, magnetic shielding equipment, electronic devices, petroleum and chemical pipeline and equipment, automobile parts, etc.

[0003] Electroless nickel plating is a thermodynamically unstable system, and there are often microparticles such as colloidal particles and solid impurities in the bath. These microparticles have high surface activity. After adding stabilizer, the stabilizer will preferentially adsorb microparticles, inhibit the action of microparticles and nickel ions, so that nickel-phosphorus co-deposition only occurs on the surface of the plated substrate material. By adding stabilizer, the stability of the bath is improved, and the utilization rate of nickel ions in the bath is also improved, so that the coating has high hardness, high wear resistance and high corrosion resistance. Moreover, the electroless nickel coating has inherent lubricity and anti-metal wear, which is different from electroplated nickel.

[0004] High-phosphorus electroless nickel is replacing the traditional hard chromium plating process, but it is found that the bath is easy to decompose, the plating speed is slow, the coating is easy to grow burrs when the coating is thick, and the burrs need to be polished repeatedly by hand, which not only wastes materials, but also delays production. Therefore, a new type of stabilizer needs to be developed to improve the utilization rate of nickel ions and eliminate burrs to the greatest extent, and improve the stability and gloss of the coating. SUMMARY

[0005] In view of the above situation, the present application provides a kind of high phosphorus thick nickel plating process without burr.

[0006] The high-phosphorus electroless nickel plating process without burr of the present application comprises the following steps:

[0007] Step 1: metal substrate pretreatment

[0008] After polishing, degreasing and washing the surface of the metal substrate, the surface is activated by hydrofluoric acid, and then washed before use;

[0009] Step 2: Preparation of plating solution

[0010] Per liter of plating solution: sodium phosphate 10-35g, nickel sulfate 20-40g, sodium hypophosphite 0.22-0.25mol, sodium fluoride 0.5-1.5g, sodium citrate 0.1-0.3mol, propionic acid 5mg, bismuth nitrate 6mg, chelidamic acid 2mg, anhydrous copper sulfate 2mg, sodium dodecyl sulfate 2mg; the prepared plating solution is filtered twice to remove impurities;

[0011] Step 3: Post-treatment of plating solution

[0012] According to the volume ratio of 1:500, the composite stabilizer C is added to the plating solution, and then the pH is adjusted to 4.6~4.8, and the water bath is heated to 85~90℃;

[0013] The composite stabilizer C is prepared by mixing stabilizer A and stabilizer B in a volume ratio of 2:1;

[0014] Step 4: Electroless nickel plating

[0015] The metal substrate pretreated in step 1 is placed in the plating solution treated in step 3, and plated for 6 hours or less; then the plated parts are cleaned and dried; during the plating process, the consumed nickel ions in the plating solution are measured by titration every hour, and the nickel ions are supplemented regularly.

[0016] The stabilizer A is composed of sodium thiosulfate and potassium iodate, wherein the concentration of sodium thiosulfate is 0.5-1mol / L, and the concentration of potassium iodate is 5-10mg / L.

[0017] The stabilizer B is composed of sodium dodecyl sulfate and ammonium molybdate, wherein the concentration of sodium dodecyl sulfate is 0.03-0.08mg / L, and the concentration of ammonium molybdate is 0.01-0.05mg / L.

[0018] The beneficial effects of the present application: sodium thiosulfate has strong complexing property, and when compounded with potassium iodate, it not only eliminates instability and retains high complexing property, but also improves the thickness and adhesion of the nickel plating layer, enhances the surface gloss, and generates no burrs. Sodium dodecyl sulfate has good penetration and dispersion performance, and has good stability in a wide range of pH values. The composite stabilizer obtained by compounding sodium dodecyl sulfate and ammonium molybdate can make the plating layer more uniform, increase the film thickness while eliminating the influence of burrs. When the stabilizer A and the stabilizer B are compounded into the composite stabilizer C in a certain proportion, the generation of burrs is overcome while the plating layer is thickened, the plating layer is uniform, the cost is low, the environment is friendly, the service life of the plated parts is long, and the utilization rate of nickel in the plating solution is high. Specific implementation method

[0019] Example 1

[0020] Effect of plating solution with composite stabilizer C added

[0021] Electroless plating process:

[0022] Step 1: Pretreatment of metal substrate

[0023] The surface of the metal substrate was polished, washed with water, blown dry, weighed, chemically degreased, washed with hot water and cold water, and then activated with hydrofluoric acid for 10-15 seconds before being washed with deionized water and used;

[0024] Step 2: Preparation of plating solution

[0025] Per liter of plating solution: sodium dihydrogen phosphate 35g, nickel sulfate 40g, sodium hypophosphite 0.25mol, sodium fluoride 1.5g, complexing agent sodium citrate 0.3mol, propionic acid 5mg, bismuth nitrate 6mg, chelidonate 2mg, anhydrous copper sulfate 2mg, and sodium dodecyl sulfate 2mg; the prepared plating solution was filtered twice to remove impurities;

[0026] Step 3: Post-treatment of plating solution

[0027] The composite stabilizer C was added to the plating solution of Step 2 according to a volume ratio of 1:500, and then the pH was adjusted to 4.6 and heated to 86°C in a water bath;

[0028] The composite stabilizer C is composed of stabilizer A and stabilizer B in a volume ratio of 2:1;

[0029] Step 4: Electroless nickel plating

[0030] The metal substrate pretreated in Step 1 was placed in the plating solution post-treated in Step 3 and plated for 6 hours; then the plated parts were removed, washed and dried; during the plating process, the consumed nickel ions in the plating solution were measured every hour using titration method, and the nickel ions were supplemented regularly.

[0031] The stabilizer B is composed of sodium dodecyl sulfate and ammonium molybdate, wherein the concentration of sodium dodecyl sulfate is 0.08mg / L and the concentration of ammonium molybdate is 0.05mg / L.

[0032] The stabilizer A is composed of sodium thiosulfate and potassium iodate, wherein the concentration of sodium thiosulfate is 1.0mol / L and the concentration of potassium iodate is 10mg / L.

[0033] The results show that the plating layer thickness reaches 80 , and there is no burr.

[0034] Example 2

[0035] Effect of plating solution with single stabilizer ammonium molybdate

[0036] Electroless plating process:

[0037] Step 1: Pretreatment of metal substrate

[0038] The surface of the metal substrate is polished, washed with water, dried, weighed, chemically degreased, washed with hot water and cold water, then activated and washed with deionized water before use.

[0039] Step 2: Preparation of plating solution

[0040] Per liter of plating solution: sodium dihydrogen phosphate 35g, nickel sulfate 40g, sodium hypophosphite 0.25mol, sodium fluoride 0.5g, sodium citrate 0.3mol, propionic acid 5mg, bismuth nitrate 6mg, chelidamic acid 2mg, anhydrous copper sulfate 2mg, sodium dodecyl sulfate 2mg; The prepared plating solution is filtered twice to remove impurities.

[0041] Step 3: Post-treatment of plating solution

[0042] Ammonium molybdate is added to the plating solution of step 2, and then the pH is adjusted to 4.6 and heated to 86°C in a water bath; wherein the concentration of ammonium molybdate in the plating solution is 0.1mg / L;

[0043] Step 4: Electroless nickel plating

[0044] The pretreated metal substrate of step 1 is placed in the post-treated plating solution of step 3 and plated for 6 hours; then the plated parts are removed, washed and dried; During plating, the consumed nickel ions in the plating solution are measured every hour by titration, and the nickel ions are supplemented regularly.

[0045] The results show that the thickness of the plating layer reaches 56 , with burrs.

[0046] Example 3

[0047] Effect of plating solution with stabilizer A

[0048] Electroless plating process:

[0049] Step 1: Pretreatment of metal substrate

[0050] The surface of the metal substrate is polished, washed with water, dried, weighed, chemically degreased, washed with hot water and cold water, then activated and washed with deionized water before use.

[0051] Step 2: Preparation of plating solution

[0052] Sodium dihydrogen phosphate 35 g, nickel sulfate 40 g, sodium hypophosphite 0.25 mol, sodium fluoride 1.5 g, sodium citrate 0.3 mol, propionic acid 5 mg, bismuth nitrate 6 mg, chelidonate 2 mg, anhydrous copper sulfate 2 mg, sodium dodecyl sulfate 2 mg per liter of plating solution; the above prepared plating solution is filtered twice to remove impurities;

[0053] Step 3: Post-treatment of plating solution

[0054] Stabilizer A is added to the plating solution of Step 2, and then the pH is adjusted to 4.6 and heated to 86°C in a water bath.

[0055] The metal substrate pretreated in Step 1 is placed in the plating solution post-treated in Step 3 and plated for 6 hours; then the plated part is taken out for cleaning and drying; during plating, the consumed nickel ions in the plating solution are measured by titration every hour, and the nickel ions are supplemented regularly.

[0056] The results show that the plating layer thickness reaches 58 , without burrs.

[0057] Example 4

[0058] Effect of plating solution with stabilizer B

[0059] Chemical plating process:

[0060] Step 1: Pretreatment of metal substrate

[0061] The surface of the metal substrate is polished, washed with water, blown dry, weighed, chemically degreased, washed with hot water and cold water, then activated, cleaned with deionized water, and ready for use;

[0062] Step 2: Preparation of plating solution

[0063] Sodium dihydrogen phosphate 35 g, nickel sulfate 40 g, sodium hypophosphite 0.25 mol, sodium fluoride 1.5 g, sodium citrate 0.3 mol, propionic acid 5 mg, bismuth nitrate 6 mg, chelidonate 2 mg, anhydrous copper sulfate 2 mg, sodium dodecyl sulfate 2 mg per liter of plating solution; the above prepared plating solution is filtered twice to remove impurities;

[0064] Step 3: Post-treatment of plating solution

[0065] Stabilizer B is added to the plating solution of Step 2, and then the pH is adjusted to 4.6 and heated to 86°C in a water bath.

[0066] The metal substrate pretreated in Step 1 is placed in the plating solution post-treated in Step 3 and plated for 6 hours; then the plated part is taken out for cleaning and drying; during plating, the consumed nickel ions in the plating solution are measured by titration every hour, and the nickel ions are supplemented regularly.

[0067] The results show that the coating thickness reaches 68 No burr.

Claims

1. A process for plating thick nickel on high phosphorus substrates without burr, characterized by: The process comprises the following steps: Step 1: Pretreatment of metal substrate After polishing, degreasing and washing the surface of the metal substrate, activate it with hydrofluoric acid, then wash it again and wait for use; Step 2: Preparation of plating solution Per liter of plating solution: sodium dihydrogen phosphate 10-35g, nickel sulfate 20-40g, sodium hypophosphite 0.22-0.25mol, sodium fluoride 0.5-1.5g, sodium citrate 0.1-0.3mol, propionic acid 5mg, bismuth nitrate 6mg, chelidamic acid 2mg, anhydrous copper sulfate 2mg, sodium dodecyl sulfate 2mg; filter the above prepared plating solution twice to remove impurities; Step 3: Post-treatment of plating solution According to the volume ratio of 1:500, add composite stabilizer C to the plating solution, then adjust the pH to 4.6~4.8, and heat in water bath to 85~90℃; The composite stabilizer C is compounded by stabilizer A and stabilizer B according to the volume ratio of 2:1; Step 4: Electroless nickel plating Put the pretreated metal substrate in step 1 into the plating solution treated in step 3, and plate for 6 hours or less; then take out the plated parts for cleaning and drying; during plating, the consumed nickel ions in the plating solution are measured by titration every hour, and nickel ions are supplemented regularly; The stabilizer A is composed of sodium thiosulfate and potassium iodate, wherein the concentration of sodium thiosulfate is 0.5-1mol / L, and the concentration of potassium iodate is 5-10mg / L; The stabilizer B is composed of sodium dodecyl sulfate and ammonium molybdate, wherein the concentration of sodium dodecyl sulfate is 0.03-0.08mg / L, and the concentration of ammonium molybdate is 0.01-0.05mg / L.