CN100462485C - Composite brightener for alkaline electroless nickel plating and its application method - Google Patents

Abstract

The invention discloses an alkaline electroless nickel plating composite brightener and a using method thereof. It is based on 1 liter, and it is a composite brightener composed of primary brightener content of 10-20g, secondary brightener content of 25-50g and auxiliary brightener content of 30-52g, and the rest is water. The method of use is to slowly add the composite brightener to the chemical plating solution, and adjust the pH value to 8.0-11.0 with a 5%-10% volume percentage of dilute ammonia solution; the plating temperature is 40-80°C; after degreasing and pickling 1. After immersing the activated parts in the plating solution for 10-150 minutes, a bright nickel plating layer can be obtained on the surface of the parts. The invention can not only significantly improve the brightness of the plating layer, but also help reduce the porosity of the plating layer; the light output is fast, the dispersion ability is good, the stability of the plating solution can be improved, and the service life of the plating solution can be improved. The decomposition products of the brightener do not affect the composition of the plating solution and the The quality of the parts; the coating is dense, the surface stress is low, and the toughness is good.

Description

Composite brightener for alkaline electroless nickel plating and its application method

technical field

The invention relates to the technical field of chemical surface treatment of metal materials, in particular to an alkaline electroless nickel plating composite brightener and a use method thereof.

Background technique

Electroless nickel-phosphorus alloy, as a new type of excellent engineering material, has become the focus of research and development by domestic and foreign scientific research institutes and production enterprises. It is an emerging surface treatment technology that uses oxidation-reduction reaction to deposit a layer of alloy coating on the catalytic surface. The obtained electroless nickel-phosphorus alloy coating has good corrosion resistance and wear resistance, uniform coating thickness and high hardness. , and good imitation, and thus widely used in chemical machinery, aerospace and other fields.

For a long time, the electroless nickel plating process, especially the domestic production process, mainly adopts the acidic Ni-P alloy process with high temperature and dullness. Although its deposition speed is fast and its corrosion resistance is good, it needs high temperature (above 90°C) to Plating requires high energy consumption, poor coating brightness, poor stability of the plating solution, severe self-decomposition of the solution, and incomplete solution of replenishment and regeneration of the solution. Many manufacturers can only adopt one-time plating. The phosphorus content in the coating obtained from the alkaline electroless nickel plating solution is lower than that of the acid plating solution, the gloss is still relatively poor, and the coating porosity is relatively large, so the corrosion resistance is poor, but the solution is relatively stable and easy to operate. Low, some processes can be carried out at room temperature. In order to solve the problem of poor brightness of alkaline electroless nickel plating and expand the industrial application range of alkaline electroless nickel plating, it is very necessary to study a brightener suitable for alkaline electroless nickel plating. Due to the complex composition of the electroless plating bath, there are many influencing factors, and the pH value in the alkaline electroless plating bath is relatively high, so the development of the brightener for alkaline electroless nickel plating must fully consider the various components in the brightener and the various ions in the plating bath. In order to give full play to the advantages of alkaline electroless nickel plating and the effect of brightener, the interaction of the interaction and the influence of high pH value.

Contents of the invention

The object of the present invention is to provide an alkaline electroless nickel plating composite brightener with good brightness and leveling property, fast light output speed and no harm to plating solution components and plated parts quality and its application method.

Alkaline electroless nickel plating composite brightener is calculated in 1 liter. It is composed of primary brightener content of 10-20g, secondary brightener content of 25-50g and auxiliary brightener content of 30-52g, and the rest is composed of water Composite brightener; the primary brightener is saccharin, its content is 10-20g, the primary brightener is composed of saccharin and sodium benzenesulfinate, wherein, the content of saccharin is 5-15g, and the content of sodium benzenesulfinate is 5-15g ; The secondary brightener consists of 1,4-butynediol, pyridine and thiourea, wherein the content of 1,4-butynediol is 5-10g, the content of pyridine is 20-40g, and the content of thiourea is 0.5- 1g; the auxiliary brightener is composed of sodium allyl sulfonate and sodium propyne sulfonate, wherein the content of sodium allyl sulfonate is 30-50g, and sodium propyne sulfonate is 0.5-2g.

The method of using the composite brightener for alkaline electroless nickel plating: Take 2-4ml composite brightener and slowly add it to 1 liter of electroless plating solution, and adjust the pH value to 8.0-11.0 with 5%-10% ammonia solution; the plating temperature is 40-80°C; Immerse the parts after degreasing, pickling and activation treatment in the plating solution for 10-150 minutes, and a bright nickel plating layer can be obtained on the surface of the parts.

Compared with prior art, the present invention has following advantage:

1. It can not only significantly improve the brightness of the coating and increase the leveling of the coating, but also help reduce the porosity of the coating;

2. Fast light emission and good dispersion ability can improve the stability of the plating solution and prolong the service life of the plating solution. The decomposition products of the brightener will not affect the composition of the plating solution and the quality of the plated parts;

3. The coating is dense and flat, with low surface stress and good toughness.

Detailed ways

The present invention adopts alkaline electroless nickel plating solution as the basic formula, and adds a composite brightener compounded by several electroplating nickel intermediates and other additives. The formed coating has a bright mirror surface, fine cells on the surface, and good bonding force of the coating. Surface porosity is low. The plating solution has good stability.

Alkaline electroless nickel plating composite brightener of the present invention is in 1 liter, and it is 10-20g by primary brightener content, and secondary brightener content is 25-50g and auxiliary brightener content is 30-52g, and all the other are Composite brightener composed of water. The primary brightener is saccharin (C ₇ H ₅ NO ₃ S) with a content of 10-20g. The primary brightener is composed of saccharin and sodium benzenesulfinate (C ₆ H ₅ NaO ₂ S), and the content of saccharin is 5 -10g, the content of sodium benzenesulfinate is 5-10g; the secondary brightener consists of 1,4-butynediol (HOCH ₂ CCCH ₂ OH), pyridine (C ₅ H ₅ N) and thiourea ((NH ₂ ) ₂ CS), wherein the content of 1,4-butynediol is 5-10g, the content of pyridine is 20-40g, and the content of thiourea is 0.5-1g; the auxiliary brightener is sodium allyl sulfonate (CH ₂ CHCH ₂ SO ₃ Na) and sodium propyne sulfonate (HC=C-CH ₂ -SO ₃ Na), wherein the content of sodium allyl sulfonate is 30-50g, and the content of sodium propyne sulfonate is 0.5-2g . Slowly add 2-4ml composite brightener to every 1 liter of alkaline electroless nickel plating solution to get a bright electroless nickel plating layer.

Among the above components, the main function of the primary brightener is to refine the grains and reduce the brittleness of the coating. With the increase of the addition amount, the tensile stress of the coating decreases and gradually shifts to compressive stress; the primary brightener can also reduce the sensitivity of the plating solution to metal impurities. Sexuality. According to the electrochemical mechanism of electroless nickel plating, there is a cathode area on the plated parts. When saccharin and sodium benzenesulfinate in the primary brightener are adsorbed in the cathode area of the plated parts, and react to generate a small amount of sulfur, sulfur and nickel will form Co-deposit and interact to form compounds, so that the volume of the deposited layer expands, and the substrate restricts this expansion, generating a compressive stress distribution in the deposited layer, offsetting part of the tensile stress in the deposited layer, and reducing the internal stress of the coating. At the same time, the primary brightener affects the deposition of nickel ions and improves the dispersion ability of the plating solution, thus changing the physical properties of the nickel plating layer, refining the metal crystals and changing the orientation of the crystal plane.

The secondary brightener can make the coating produce obvious luster, but at the same time it brings the tensile stress, brittleness and sensitivity to impurities of the coating. Through reasonable cooperation with the primary brightener, a fully bright coating can be produced. The 1,4-butynediol in the secondary brightener can make the coating produce obvious white luster, but the leveling property is poor, and it can be used in conjunction with sodium propyne sulfonate and sodium allyl sulfonate in the auxiliary brightener , can greatly improve the leveling performance; pyridine itself has good brightness and leveling performance, but in order to prevent or reduce missing plating, a small amount of thiourea is added to cooperate with it; thiourea can prevent or reduce missing plating and improve the resistance to heavy metal impurities Tolerance, thiourea also acts as a stabilizer to stabilize the plating solution within a certain range, but if the amount exceeds a certain amount, the plating speed will be reduced, so the amount used in the electroless nickel plating solution is less. The secondary brightener changes the surface state by adsorbing on the micro-cathode area of the catalytic surface, making hydrogen easy to precipitate, which is conducive to fine crystallization.

The auxiliary brightener only plays an auxiliary role in the brightening of the coating, and has a good dispersion effect, which is beneficial to improving the covering ability of the coating and reducing the sensitivity of the plating solution to metal impurities.

The method of using the above-mentioned brightener: slowly add the prepared brightener into the electroless plating solution according to the regulations, and adjust the pH value to 8.0-11.0 with 5%-10% dilute ammonia solution; heat to 40-80°C; Immerse the degreased, pickled and activated parts in the plating solution for 10-150 minutes, and a mirror-bright nickel layer can be obtained on the surface of the parts.

For coordinating the implementation of the present invention, adopting the alkaline electroless nickel plating solution that has been applied industrially is the basic plating solution, and concrete formula and plating condition are as follows:

Nickel sulfate hexahydrate (NiSO ₄ ·6H ₂ O) 25g/l

Sodium hypophosphite (NaH ₂ PO ₂ ·H ₂ O) 20g/l

Sodium citrate (Na ₃ C ₆ H ₅ O ₇ 2H ₂ O) 11g/l

Ammonium chloride (NH ₄ OH) 50g/l

Use 5%-10% dilute ammonia solution to adjust the pH value of the plating solution.

Prepare 250ml of plating solution according to the above formula, and use 30mm×30mm×3mm 45# steel as the substrate to carry out the test. plating.

According to the brightener type and the composition range of the present invention, prepare the electroless nickel plating composite brightener of the present invention of different components respectively, as shown in the following table 1, add in the above-mentioned basic plating solution and mix homogeneously, then according to the conditions of the claims Plating, the technology of specific embodiment is as shown in table 2.

The plating speed of electroless plating is measured by weighing method, and the porosity of the coating is measured by sticking filter paper. The components of the corrosion solution are potassium ferricyanide 10g/l, sodium chloride 20g/l, and the sticking time is 5min.

Table 1. Formula table of brighteners with different components

Table 2. Plating process table of each embodiment

formula Dosage(ml/l) pH value temperature(℃) Example 1 Recipe 1 2 8.0 40 Example 2 Recipe 1 4 11.0 80 Example 3 Recipe 1 3 9.0 60 Example 4 Recipe 1 3 10.0 70

Example 5 Recipe 2 2 8.0 60 Example 6 Recipe 2 3 10.0 70 Example 7 Recipe 2 4 8.0 50 Example 8 Recipe 3 2 10.0 65 Example 9 Recipe 3 3 8.0 40 Example 10 Recipe 3 4 9.5 70 Example 11 Recipe 4 2 10.0 70 Example 12 Recipe 4 3 11.0 50 Example 13 Recipe 4 4 10.0 60 Example 14 Recipe 5 2 9.0 80 Example 15 Recipe 5 3 8.5 80 Example 16 Recipe 5 4 8.0 80 Example 17 Recipe 6 2 11.0 50 Example 18 Recipe 6 3 11.0 65 Example 19 Recipe 6 4 9.0 40

After plating, evaluate the brightness of the coating and test the plating speed and porosity of the coating as shown in Table 3 below.

Table 3. The coating performance of each embodiment gained

Example Plating Appearance Plating speed(um/h) Coating porosity (pcs/cm²) Without brightener off-white, rough 14.8 2.4 Example 1 Bright white, uniform color, smooth 11.2 0.6 Example 2 Bright, milky white, smooth 14.7 1.2 Example 3 Bright, slightly white, flat 12.8 0.8 Example 4 Bright, slightly white, flat 13.7 1.0 Example 5 Bright, light yellow, uniform color 11.5 0.3 Example 6 Bright, light yellow, uniform color 11.5 0.5 Example 7 Bright, light yellow, uniform color 9.8 0.3 Example 8 Mirror bright, uniform color, smooth 12.6 0.0 Example 9 Mirror bright, uniform color, smooth 9.5 0.1 Example 10 Mirror bright, uniform color, smooth 13.4 0.1 Example 11 Mirror bright, uniform color, smooth 12.3 0.0 Example 12 Mirror bright, uniform color, smooth 10.0 0.0 Example 13 Mirror bright, light yellow, smooth 12.3 0.1 Example 14 Bright, slightly yellowish, flat 13.8 0.2 Example 15 Bright, slightly yellowish, smooth 13.0 0.3 Example 16 Bright, slightly yellowish, smooth 13.6 0.3 Example 17 Mirror bright, uniform color, smooth 9.6 0.0 Example 18 Mirror bright, uniform color, smooth 11.9 0.1 Example 19 Bright, uniform color, smooth 10.6 0.4

As can be seen from Table 3, after adding the brightener of the present invention, the sample surface is brighter and smoother than when no brightener is added, and the color is uniform, and can obviously reduce the porosity of the coating surface, which has a great effect on improving the corrosion resistance of the coating. help.

Claims (4)

1. an alkali compound brightening agent for chemical plating of nickel is characterized in that, in 1 liter, it is to be 10-20g by elementary bright agent content,, second-class brightener content is that 25-50g and auxiliary brightener content are 30-52g, the composite brightening agent that all the other are formed for water; Elementary brightening agent is a soluble saccharin, and its content is 10g or 20g, and perhaps elementary brightening agent is made up of soluble saccharin and benzene sulfinic acid sodium salt, and wherein, soluble saccharin content is 10g, 5g, 15g or 8g, and the benzene sulfinic acid sodium content is 10g, 10g, 5g or 8g; Second-class brightener is by 1, and 4-butynediol, pyridine and thiocarbamide are formed, wherein, 1,4-butynediol content is 5-10g, and pyridine content is 20-40g, and thiocarbamide content is 0.5-1g; Auxiliary brightener is made up of sodium allyl sulfonate and propine sodium sulfonate, and wherein, the allyl sulphonic acid sodium content is 30-50g, propine sodium sulfonate 0.5-2g.

2. the using method of an alkali compound brightening agent for chemical plating of nickel as claimed in claim 1 is characterized in that, gets the 2-4ml composite brightening agent and slowly adds in 1 liter of chemical plating bath, and regulate the pH value to 8.0-11.0 with the ammonia soln of 5%-10%; Plating temperature is 40-80 ℃; To immerse 10-150min in the plating bath through the part of oil removing, pickling, activation treatment, can obtain the nickel layer of light at piece surface.

3. the using method of a kind of alkali compound brightening agent for chemical plating of nickel according to claim 2 is characterized in that, described pH value is 9.0-10.0.

4. the using method of a kind of alkali compound brightening agent for chemical plating of nickel according to claim 2 is characterized in that, described plating temperature is 60-70 ℃.