Electroless Nickel Plating Guide: Advantages, Applications & Differences Between Electrolytic

In the metal surface treatment process, electroless nickel plating is a relatively common treatment process. At present, the application of electroless nickel plating is very extensive. The shadow of electroless nickel plating can be seen in electronic components, mechanical processing, mold, the automobile industry, and other industries. Today, you’re going to learn electroless nickel plating’s advantages, applications and differences between electrolytic nickel plating.

Advantages of electroless nickel plating

1.Thickness uniformity

Uniform thickness and good uniform plating ability are one of the characteristics of electroless nickel plating, which is also one of the reasons for its wide application. Electroless nickel plating avoids the uneven thickness of the electroplated rubber coating due to the uneven current distribution. The thickness of the electroplated coating varies greatly on the whole part, especially on the parts with complex shapes. At the corners of the parts and the parts close to the anode, the coating is thicker, while the coating on the inner surface or the parts far from the anode is very thin, or even can not be plated, This deficiency of electroplating can be avoided by using electroless plating. During electroless plating, as long as the part surface contacts with the plating solution, the components consumed in the plating solution can be supplemented in time, and the coating thickness of any part is basically the same, even the groove, gap and blind hole.

2. There is no problem of hydrogen embrittlement

Electroplating is the use of power to convert nickel cations into metallic nickel and deposit it on the anode. The method of chemical reduction is to reduce nickel cations into metallic nickel and deposit it on the surface of the base metal. The test shows that the inclusion of hydrogen in the coating has nothing to do with the chemical reduction reaction, but has a great relationship with the electroplating conditions. Generally, the hydrogen content in the coating increases with the increase of current density.

In the nickel plating solution, except for a small part of hydrogen generated by the reaction of NiSO4 and H2PO3, most hydrogen is generated by the hydrolysis caused by the electrode reaction when the two poles are energized. In the anode reaction, a large amount of hydrogen is generated. The hydrogen on the cathode and the metal Ni-P alloy precipitate at the same time to form (Ni-P) H, which is attached to the deposition layer. Because of the formation of an excessive amount of atomic hydrogen on the cathode surface, a part of hydrogen is desorbed to form H2, However, if there is no time to desorb, it will remain in the coating.

A part of the hydrogen left in the coating will diffuse into the base metal, while the other part of the hydrogen will gather at the defects of the base metal and the coating to form a hydrogen mass, which has a high pressure. Under the pressure, the defects will cause cracks, and under the stress, the fracture source will be formed, resulting in hydrogen embrittlement fracture. Hydrogen not only penetrates into the base metal, but also into the coating. It is reported that nickel electroplating should be conducted at 400 ℃ × 18h or 230 ℃ × After 48h of heat treatment, the hydrogen in the coating can be basically removed, so it is very difficult to remove hydrogen by electroplating nickel, while it is not necessary to remove hydrogen by electroless nickel plating.

3. The functions of many materials and parts, such as corrosion resistance and high temperature oxidation resistance, are reflected by the surface layer of materials and parts. In general, some chemical nickel coating with special functions can be used to replace the whole solid material prepared by other methods, or the cheap base material chemical nickel plating can be used to replace the parts made of valuable raw materials. Therefore, the economic benefits of chemical nickel plating are very great.

4. It can be deposited on the surface of various materials, such as steel nickel-based alloy, zinc-based alloy, glass, ceramic, plastic, semiconductor and other materials, thus creating conditions for improving the performance of these materials.

5. It does not need the DC motor or control equipment required for general electroplating, and the heat treatment temperature is low. As long as the temperature is below 400 ℃ and the heat preservation time is different, different corrosion resistance and wear resistance can be obtained. Therefore, it does not have the problem of heat treatment deformation, and is especially suitable for processing some parts with complex shape and surface requirements of wear and corrosion resistance.

Applications of electroless nickel plating

Chemical nickel plating treatment is to use chemical nickel plating solution to coat a layer of nickel on the metal surface to prevent the contact between corrosive substances and the metal substrate, protect the metal substrate, and achieve the effect of surface rust prevention. Electroless nickel plating can effectively improve the performance of electronic products.

After electroless nickel plating, metal products and components can be significantly improved in terms of wear resistance and corrosion resistance. Especially in mechanical hard disk, pcb circuit board, resistance components, metal components, etc., the components after electroless nickel plating can effectively improve corrosion resistance, wear resistance and other properties.

Electroless nickel plating can effectively improve the service life of mechanical manufacturing parts. The mechanical parts, such as transmission chain, gear, hydraulic shaft and so on, which have been chemically plated with nickel can effectively improve their wear resistance and corrosion resistance, and obtain a longer service life.

Difference between electroless nickel plating and electrolytic nickel plating

1. The difference between electroless plating and electroplating in principle is that electroplating requires additional current and anode, while electroless plating depends on the autocatalytic reaction on the metal surface.

2. The electroless nickel coating is extremely uniform. As long as the plating solution can be soaked and the solute exchange is sufficient, the coating will be very uniform and can almost achieve the effect of profiling.

3. Electroplating can not be used for full-surface plating of some workpieces with complex shapes, but chemical plating has been used for plating of workpieces with any shape.

4. The electroless nickel coating with high phosphorus content is amorphous, and there is no crystal gap on the coating surface, while the electrodeposited coating is a typical crystalline coating.

5. Because of the applied current, the plating speed is faster than that of chemical plating, and the plating of the same thickness should be completed earlier than that of chemical plating.

6. The adhesion of electroless plating is generally higher than that of electroplating.

7. Because most of the electroless plating uses food-grade additives and does not use harmful substances such as cyanide, electroless plating is more environmentally friendly than electroplating.