CN106048568B - The method of environmentally friendly chemical nickel plating - Google Patents

Abstract

The invention discloses an environment-friendly electroless nickel plating method. The present invention finds that benzimidazole and potassium iodide-copper sulfate composite have stabilizing effect and brightening effect respectively on citric acid system electroless nickel plating, the present invention uses benzimidazole as the stabilizer of citric acid electroless nickel plating system, potassium iodide and copper sulfate composite Brightener, all raw and auxiliary materials and additives are easy to purchase, the plating process is simple and easy to operate, the plating solution does not contain toxic and harmful heavy metal ions such as Pb ²⁺ and Cd ²⁺ , the coating has high corrosion resistance and brightness, and is an environmentally friendly This type of surface treatment technology can be used to plate nickel-phosphorus alloy coating on the surface of carbon steel, aluminum alloy and other materials, which has potential application prospects and economic benefits. When the invention is used for laboratory plating, the service life of the plating solution can reach 8 metal cycles, the corrosion resistance time of the plating layer in neutral salt spray is more than 48 hours, and the brightness of the plating layer can reach 208Gs.

Description

Environmentally Friendly Electroless Nickel Plating Method

technical field

The invention belongs to the technical field of material science, in particular to an environment-friendly electroless nickel plating method.

Background technique

Electroless nickel plating technology has many advantages such as good corrosion resistance, high hardness, uniform coating, and uniform coating on the surface of parts with complex shapes. It is widely used in aviation, aerospace, automobile manufacturing, chemical and other industries. However, in the traditional electroless nickel plating process, divalent lead ions are often used as stabilizers and divalent cadmium ions as brighteners, so that the plating solution and wastewater contain toxic and harmful heavy metal ions such as Pb ²⁺ , Cd ²⁺ , and subsequent wastewater treatment is a heavy burden. , does not conform to the development trend of green surface treatment technology.

The currently adopted solutions are: add thiourea or its derivatives as stabilizer in the electroless nickel plating solution, and add stannous sulfate as brightener, in order to reduce the content of divalent lead and divalent cadmium in the plating solution as much as possible. However, the above methods mainly have the main problem of low corrosion resistance of the coating (the neutral salt spray corrosion resistance time is less than 48 hours).

Contents of the invention

The object of the present invention is: provide a kind of method of environment-friendly electroless nickel plating, its plating solution does not contain poisonous and harmful heavy metal ions such as Pb ²⁺ , Cd ^{2 +} , and plating solution stability, coating corrosion resistance and brightness The performance is no less than that of the traditional citric acid system electroless nickel plating process, so as to overcome the shortcomings of the existing technology.

The present invention is achieved in that the method for environment-friendly electroless nickel plating comprises the steps:

1) Put the prepared basic plating solution into a constant temperature water bath, stir and heat up to 85-90°C;

2) The plated sheet is polished, degreased, washed, surface activated, and washed again to achieve pretreatment;

3) Put the pretreated plated sheet into the basic plating solution for electroless nickel plating;

4) then immerse the plated sheet through electroless nickel plating in the chromate solution for passivation treatment;

5) The plated sheet after passivation is washed with deionized water and dried, and the electroless nickel plating process is completed.

The configuration of 50L basic plating solution includes the following steps;

a) Dissolve 10-15kg of nickel sulfate hexahydrate in 30-40L of deionized water. After the dissolution is completed, add 4-5kg of citric acid monohydrate, 1.5-2.5L of auxiliary complexing agent and 1-1.5g of stabilizer under stirring , after mixing evenly, dilute to 50L with pure water, and then adjust the pH value to 4.58-4.62 to obtain liquid A;

b) Dissolve 7-9kg of sodium hypophosphite in 30-40L of deionized water. After the dissolution is complete, add 3.5-4kg of crystalline sodium acetate, 3-3.5kg of citric acid monohydrate, and 1.4-1.8L of auxiliary complexing agent under stirring , 1.5-2g stabilizer, 2-3g 2-ethylhexyl sodium sulfate and 13-18g brightener, after stirring and mixing evenly, dilute to 50L with pure water to obtain liquid B;

c) Under stirring, put 14-16kg sodium hypophosphite monohydrate into 30-40L deionized water, add 6-7kg crystalline sodium acetate, 1-2g 2-ethylhexyl sodium sulfate and 6-8g brightener, stir and mix After uniformity, dilute to 50L with pure water to obtain liquid C;

4) Add 5L liquid A and 10L pure water into the plating tank, add 10L liquid B under stirring conditions, mix well and test the pH value to be 4.58-4.62, set the volume to 50L, and heat to the specified temperature for electroless nickel plating operate.

The auxiliary complexing agent is 88% lactic acid by mass percentage, the stabilizer is benzimidazole; the brightener is potassium iodide and copper sulfate, and the mass ratio of potassium iodide and copper sulfate is 8-15:30 ~60; the wetting agent is OP-10.

Perform electroless nickel plating as described in step 3), specifically, heat the basic plating solution in the plating tank to 85-90°C and perform electroless nickel plating operation; Add liquid A and liquid C at a volume ratio of 1-2% of the initial volume of the basic plating solution, and use 1+1 ammonia water to adjust the pH value.

Owing to having adopted above-mentioned technical scheme, compared with prior art, the present invention screens out the stabilizing agent and the brightener that are applicable to citric acid system electroless nickel plating from a large amount of substances, to replace traditional divalent lead ion and cadmium ion, and It has been successfully applied to the actual production of electroless nickel plating on aluminum alloys and achieved good results. Find that benzimidazole and potassium iodide-copper sulfate composite have stabilizing action and brightening effect respectively to citric acid system electroless nickel plating, the present invention uses benzimidazole as the stabilizer of citric acid electroless nickel plating system, and potassium iodide and copper sulfate compound make brightener , all raw and auxiliary materials and additives are easy to purchase, the plating process is simple and easy to operate, the plating solution does not contain toxic and harmful heavy metal ions such as Pb ²⁺ , Cd ²⁺ , the coating has high corrosion resistance and is bright, and is an environmentally friendly surface The treatment technology can be used to plate nickel-phosphorus alloy coating on the surface of carbon steel, aluminum alloy and other materials, which has potential application prospects and economic benefits. When the invention is used for laboratory plating, the service life of the plating solution can reach 8 metal cycles, the corrosion resistance time of the plating layer in neutral salt spray is more than 48 hours, and the brightness of the plating layer can reach 208Gs.

Detailed ways

Embodiments of the invention: a method for environmentally friendly electroless nickel plating,

1. Liquid preparation and tank preparation method

(1) Preparation of liquid A (for tank preparation and addition, based on the preparation of 50L)

Dissolve 12.5kg of nickel sulfate (hexahydrate) in 35L of pure water. After dissolving, add 4.5kg of citric acid (monohydrate), 2.0L of lactic acid (88%), and 1.25g of benzimidazole. Stir and mix well, then add water to 50L , adjust the pH value to 4.60±0.02 with 20% sodium hydroxide solution and 1+1 ammonia water, and save it for later use;

(2) Preparation of liquid B (for tank preparation, calculated on the basis of preparation of 50L)

First dissolve 7.5kg of sodium hypophosphite with about 35L of pure water. After dissolving, add 3.75kg of crystalline sodium acetate, 3.25kg of citric acid (monohydrate), 1.5L of lactic acid, 1.875g of benzimidazole, and 2-ethyl Sodium hexyl sulfate 2.5g, potassium iodide 2.5g, copper sulfate (pentahydrate) 12.5g, stir well and mix evenly, dilute to 50L.

(3) Preparation of liquid C (for addition, the ratio of addition to liquid A is 1:1, based on the preparation of 50L)

Dissolve 15.0kg of sodium hypophosphite (monohydrate) with 35L of pure water. After dissolving, add 6.5kg of crystalline sodium acetate, 1.5g of 2-ethylhexyl sodium sulfate, 1.5g of potassium iodide, and 5.5g of copper sulfate (pentahydrate). After stirring and mixing evenly, set the volume to 50L for later use.

(4) Matching tank (calculated based on the preparation of 50L)

Add 5L of liquid A to the plating tank, then add 10L of pure water, add 10L of prepared liquid B under stirring conditions, mix well and test the pH value (normally around 4.6), adjust to 4.60, and set the volume to 50L.

(5) Plating

The bath can be heated to 87°C for electroless nickel plating. During the plating process, add 375 mL each of liquid A and liquid C and 120 mL of 1+1 ammonia water into the plating tank every 30 minutes.

The auxiliary complexing agent is 88% lactic acid by mass percentage, the stabilizer is benzimidazole; the brightener is potassium iodide and copper sulfate, and the mass ratio of potassium iodide and copper sulfate is 8-15:30 ~60; the wetting agent is OP-10.

2. Bath maintenance

(1) The consumption of metal nickel in the plating solution is supplemented by liquid A, and the consumption of reducing agent (sodium hypophosphite) is supplemented by liquid C. In order to stabilize the composition of the plating solution, it is necessary to regularly (times/2h) analyze the nickel (II) ion concentration, hypophosphite ion concentration and pH value in the plating solution, and adjust the addition of A solution, C solution and ammonia water according to the analysis results. When adding, add liquid A first, then liquid C.

(2) After entering the fourth cycle, due to the accumulation of phosphite, the plating speed will slow down, and the plating speed can be increased by increasing the main salt concentration or temperature, but the temperature must be increased carefully, see Table 1 for details.

(3) When the plating solution stops working, the temperature of the plating solution should be lowered to about 60°C. When it is found that the plating solution becomes thicker due to water volatilization, add pure water to the working volume in time.

(4) The plating solution should be filtered continuously (filtering frequency not less than 2 times/hour) to remove possible fine particles.

(5) The process parameter control reference value of each cycle is as follows:

Table 1 Parameter control table for each cycle

The present invention once carried out scale-up experiment in the factory, and each technical index all reaches expected value.

The invention is suitable for plating nickel-phosphorus alloy coating on the surface of carbon steel, aluminum alloy and other metal materials. Various raw materials and additives are easy to purchase, easy to use, and can greatly reduce the cost of plating. Feasible technology, with good application prospects and economic benefits.

Claims (2)

1. a method for environment-friendly electroless nickel plating, is characterized in that: comprise the steps: 1) Put the prepared basic plating solution into a constant temperature water bath, stir and heat up to 85-90°C; 2) The plated sheet is polished, degreased, washed, surface activated, and washed again to achieve pre-treatment; 3) Put the pre-treated plate into the basic plating solution for electroless nickel plating; 4) Then immerse the electroless nickel-plated plate in the chromate solution for passivation treatment; 5) Wash the passivated plated sheet with deionized water and dry it to complete the electroless nickel plating process; The preparation of 50L basic plating solution includes the following steps; a) Dissolve 10-15kg of nickel sulfate hexahydrate in 30-40L of deionized water. After the dissolution is completed, add 4-5kg of citric acid monohydrate, 1.5-2.5L of auxiliary complexing agent and 1-1.5g of stabilizer under stirring , after mixing evenly, dilute to 50L with pure water, and then adjust the pH value to 4.58-4.62 to obtain liquid A; b) Dissolve 7-9kg of sodium hypophosphite in 30-40L of deionized water. After the dissolution is complete, add 3.5-4kg of crystalline sodium acetate, 3-3.5kg of citric acid monohydrate, and 1.4-1.8L of auxiliary complexing agent under stirring , 1.5-2g stabilizer, 2-3g 2-ethylhexyl sodium sulfate and 13-18g brightener, after stirring and mixing evenly, dilute to 50L with pure water to obtain liquid B; c) Under stirring, put 14-16kg sodium hypophosphite monohydrate into 30-40L deionized water, add 6-7kg crystalline sodium acetate, 1-2g 2-ethylhexyl sodium sulfate and 6-8g brightener, stir and mix After uniformity, dilute to 50L with pure water to obtain liquid C; d) Add 5L liquid A and 10L pure water into the plating tank, add 10L liquid B under stirring conditions, mix well and test the pH value to be 4.58-4.62, set the volume to 50 L, and heat to the specified temperature for chemical plating Nickel operations; The brightener is potassium iodide and copper sulfate, and the mass ratio of potassium iodide to copper sulfate is 8-15:30-60. 2. The method for environment-friendly electroless nickel plating according to claim 1, characterized in that: performing electroless nickel plating described in step 3), specifically, heating the basic plating solution in the plating tank to 85-90 The electroless nickel plating operation is carried out after ℃; add liquid A and liquid C to the plating tank at a volume ratio of 1:1 every 30 minutes during the plating process, and the total volume of liquid A and liquid C added each time is the initial plating solution. 1-2% of the volume, and use 1+1 ammonia water to adjust the pH value.