With the rapid development of rare earth NdFeB permanent magnet materials, the problems in NdFeB electroplating have become increasingly apparent, which has become an important factor restricting its development.
At present, the production of NdFeB electroplating mainly adopts three major processes or combination of galvanizing, "nickel + copper + nickel", and "nickel + copper + chemical nickel" plating, others such as gold plating, silver plating, tin plating, black nickel plating, etc. , Generally, additional plating is applied on the basis of the above three categories.
NdFeB magnets are mostly small workpieces (quality 0.25g ~ 20g), so the electroplating production is mainly based on barrel plating, supplemented by rack plating. However, the barrel plating of NdFeB parts is much more difficult than that of ordinary steel parts.
Difficulties in NdFeB Plating
1. Strong chemical activity of neodymium in NdFeB permanent magnet materials
NdFeB parts will produce hydrogen and corrode even in contact with water, so:
①The acid and alkali should not be too strong in the pre-plating treatment, otherwise the material matrix will be easily corroded, and because of the strong reaction between chlorine and neodymium in hydrochloric acid, hydrochloric acid should not be used;
② Choose a simple salt plating solution (such as watt nickel, potassium chloride zinc plating) when pre-plating or direct plating, it is easy to oxidize the parts and affect the bonding force between the coating and the substrate, and the parts are corroded and the plating solution is polluted;
③ It is difficult to choose a large-sized drum (which will affect the production capacity), otherwise the mixing cycle will have a greater impact and the parts will be severely oxidized.
2. NdFeB magnets are magnetic functional materials
The metal coating will affect its magnetic properties, so how to coordinate the type, combination and thickness of the coating (these properties are related to the corrosion resistance of the coating) and the magnetic properties of the product is the difficulty of NdFeB electroplating.
3. The surface of NdFeB permanent magnet is loose, porous and rough
The microscopic surface area is much larger than the macroscopic surface area, so:
①The surface dirt is not easy to clean, and the burden of pre-plating treatment is heavy;
②When pre-plating or direct plating, it is not possible to choose a complex bath with good bonding force and good corrosion resistance (due to the low current efficiency of the complex bath, it is not easy to deposit on the surface of porous parts), such as alkali copper, alkali zinc, etc. .
4. NdFeB material is brittle
Surfaces are susceptible to damage, so:
①It is more difficult for workers to operate;
②It is difficult to choose a large-sized drum (otherwise, the parts are flipped and easily bumped), which will affect the improvement of labor production efficiency.
The above is some relevant knowledge about NdFeB permanent magnets brought to you by the editor of Magnetic Han. Do you understand all of them? Pay attention to the news column of Shanghai Cihan Electronic Technology Co., Ltd., and take you to know the relevant information about various magnets.