Electroless Plating(Chemical Plating) vs Electroplating
The principle difference between electroless plating and electroplating is that electroplating requires additional current and anode, while electroless plating depends on the autocatalytic reaction on the metal surface.
The electroless nickel coating is very uniform, as long as the material can be soaked and the solute exchange is sufficient, the coating will be very uniform and can almost achieve the effect of profiling.
Electroplating can not be plating the whole surface of some workpieces with complex shapes, but electroless plating can plate workpieces of any shape.
The electroless nickel coating with high phosphorus is amorphous, there is no crystal gap on the surface of the coating, and the electroplating layer is a typical crystalline coating.
Electroplating is because of the external current, so the plating rate is much faster than electroless plating, electroplating of the same thickness should be completed ahead of time.
The adhesion of the electroless coating is generally higher than that of the electroplated coating.
Electroless plating is more environmentally friendly than electroplating because most of them use food-grade additives and do not use harmful substances such as cyanide.
At present, electroless plating has only one color of pure Ni-P alloy on the market, and electroplating can achieve many colors.
Electroless nickel plating is a method to obtain the coating by the self-catalytic reaction on the surface of the material by using metal salt and a reducing agent.
So far.
Electroless nickel plating is one of the fastest-growing surface treatment processes abroad, and it has the widest range of applications.
The rapid development of electroless nickel plating is determined by its superior process characteristics.
I. technological characteristics of electroless nickel plating.
1. Uniform thickness
uniform thickness and good uniform plating ability are one of the major characteristics of electroless nickel plating, and it is also one of the reasons for its wide application. Electroless nickel plating avoids the uneven thickness of electroplated coating caused by uneven current distribution, and the thickness of electroplated coating varies greatly in the whole part, especially on the parts with complex shapes, and the coating is thicker at the edges of the parts and near the anode.
The inner surface or far away from the anode coating is very thin, or even can not be plated, the use of electroless plating can avoid this deficiency of electroplating.
During electroless plating, as long as the surface of the part is in contact with the plating bath, the components consumed in the bath can be replenished in time, and the coating thickness of any part is basically the same, even if grooves, gaps, and blind holes are the same.
2. There is no problem with hydrogen embrittlement.
Electroplating can convert nickel cations into metal nickel and deposit them on the anode by means of chemical reduction. the experimental results show that the entrainment of hydrogen in the coating has nothing to do with the chemical reduction reaction, but has a lot to do with the electroplating conditions. the hydrogen content in the coating usually increases with the increase of current density. In a nickel plating bath, except a small part of hydrogen is produced by NiSO4 and H2PO3 reaction, most hydrogen is produced by hydrolysis caused by electrode reaction when the two poles are electrified. In the anodic reaction, hydrogen on the cathode precipitates with metal Ni-P alloy at the same time to form (Ni-P) H, which is attached to the deposition layer. Due to the formation of excess atomic hydrogen on the surface of the cathode, part of it is desorbed to form H2.
If there is no time for desorption, it remains in the coating, and part of the hydrogen left in the coating diffuses into the matrix metal, while the other part accumulates to form a hydrogen mass at the defects of the matrix metal and the coating, which has very high pressure. Under the action of pressure, the defects lead to cracks, and under the action of stress, a fracture source is formed, which leads to hydrogen embrittlement fracture.
Hydrogen permeates not only into the matrix metal but also into the coating. it is reported that electroplated nickel can basically remove hydrogen from the coating after heat treatment at 400 °℃ × 18h or 230 °℃ × 48h, so it is very difficult for electroplating nickel to remove hydrogen. however, electroless nickel plating does not need hydrogen removal.
3. The economic benefit of electroless nickel plating is very great
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 electroless nickel plating layers with special functions can be used to replace the whole solid materials prepared by other methods, and cheap matrix materials can also be used to replace parts made of valuable raw materials. Therefore, the economic benefit of electroless nickel plating is very great.
4. It can be deposited on the surfaces of various materials
It can be deposited on the surfaces of various materials, such as steel-nickel-based alloys, zinc-based alloys, glass, ceramics, plastics, semiconductors, and so on, thus creating conditions for improving the properties of these materials.
5. It does not need the DC motor or control equipment
It does not need the DC motor or control equipment needed for general electroplating, and the heat treatment temperature is low, as long as different corrosion resistance and wear resistance can be obtained after different holding times below 400 °C. Therefore, it does not have the problem of heat treatment deformation. it is especially suitable for processing parts with complex shapes and wear resistance and corrosion resistance.
6. The thickness of the chemical deposition layer can be controlled
The thickness of the chemical deposition layer can be controlled, the process is simple, the operation is convenient, the temperature is low, and the cost is lower than other surface treatment protection, so it is suitable for small and medium-sized factories or small batch production.
The respective advantages of electroplating and electroless plating:
1, process comparison:
the difference between electroless plating and electroplating in principle is that electroplating requires an external current and anode, while electroless plating depends on the autocatalytic reaction on the metal surface.
2, coating comparison:
electroless nickel coating is very uniform, as long as the bath can be soaked and the solute exchange is sufficient, the coating will be very uniform and can almost achieve the effect of profiling.
Electroplating can not be applied to the full surface of some workpieces with complex shapes, but electroless plating can be used to plate workpieces of any shape.
The electroless nickel coating with high phosphorus is amorphous, there is no crystal gap on the surface of the coating, and the electroplating layer is a typical crystalline coating.
3, electroplating speed comparison:
electroplating because of the external current, so the plating speed is much faster than electroless plating, electroplating of the same thickness should be completed ahead of time.
The adhesion of the electroless coating is generally higher than that of the electroplated coating.
4, comparison of the degree of environmental protection:
electroless plating is more environmentally friendly than electroplating because most of them use food-grade additives and do not use harmful substances such as cyanide.
5, color richness comparison:
at present, there is only one color of pure Ni-P alloy on the market, and electroplating can achieve a lot of colors.
6. Engineering and technical comparison:
electroless nickel plating is a method to obtain the coating by the self-catalytic reaction on the surface of the material by using metal salt and a reducing agent.
Up to now, electroless nickel plating is one of the fast-developing surface treatment processes abroad, and it has a wide range of applications.
The rapid development of electroless nickel plating is due to its superior process characteristics.