Neodymium Magnets are produced by powder metallurgy process, which is a kind of chemically active powder material with tiny internal pores and cavities, which is easy to be corroded and oxidized in the air. After the material is corroded or component damage, it will cause the attenuation or even loss of magnetic properties over time, thus affecting the performance and life of the whole machine, so strict anti-corrosion treatment must be carried out before use.
At present, Neodymium Magnet anti-corrosion treatment commonly used plating, chemical plating, electrophoresis, phosphating treatment, etc., of which plating as a mature means of metal surface treatment is most widely used.
Neodymium Magnet plating adopts different plating process according to the different environment of product use, and the surface plating is also different, such as zinc plating, nickel plating, copper plating, tin plating, precious metal plating, etc. Generally, zinc plating, nickel plating+copper+nickel, nickel plating+copper+chemical nickel plating are the mainstream three processes. Only zinc and nickel are suitable for direct plating on the surface of NdFeB magnets, so multi-layer plating technology is generally implemented after nickel plating. Now has broken through the NdFeB magnet direct copper plating technology difficulties, direct copper plating and then nickel plating is the development trend, so that the plating design is more conducive to the NdFeB magnet components of the thermal demagnetization indicators to reach the customer needs.
| Plating types | Characteristics and Use Environment |
| Nickel plating | Nickel is a magnetically conductive material, and the plating has a magnetic shielding effect, which has a slightly greater effect on thin products. The plating layer is more resistant to humidity, heat and high pressure accelerated aging test. It is used in atmospheric environments where condensation may occur, for customers who have high requirements for long-term stability of appearance and internal performance. |
| blue-white zinc | Zinc is a non-conducting material, and the coating has better salt spray resistance. The surface of the product is prone to powder generation after long-term use, and there are some limitations to its application. Used in environments where slight corrosion may occur, the coating has only limited corrosion resistance to short-term pollution discoloration. |
| colored zinc | Compared with blue-white zinc, the corrosion resistance is significantly improved and is suitable for use in harsher environments, such as organic corrosive environments. |
| Nickel + Copper + Nickel plating | Compared with single nickel layer, it has better corrosion resistance, but the process is relatively complicated. |
| Nickel + Tin plating | Good appearance and weldability, suitable for electrical contacts where a weldable surface is required. |
| Nickel + Silver Plating | Good appearance and solderability, low contact resistance, poor surface resistance to discoloration. It is suitable for the occasions which are in contact with electricity and require the surface to be weldable. |
| Nickel + gold plating | Good decorative, the surface is not easy to change color, small contact resistance, high cost. It is suitable for the occasions which are in contact with electricity, require the surface to be weldable, and have high requirements for the appearance of decoration. |
The corrosion resistance of different plating layers has certain differences as follows:
| Plating types | Plating code | Typical thickness(um) | Center Salt Spray Test(h) | Damp Heat Test(h) | High-pressure Accelerated Aging Test(h) | |
| Nickel plating (barrel plating) | Ni | 5-20 | 48 | 168 | 48 | |
| Nickel plating (rack plating) | Ni | 5-20 | 16 | 168 | 48 | |
| Nickel-copper-nickel plating (barrel plating) | NiCuNi | 5-20 | 48 | 168 | 48 | |
| Nickel-copper-nickel plating (rack plating) | NiCuNi | 5-20 | 16 | 168 | 48 | |
| Zinc plating | Blue-White Zinc | Zn.L | 4-15 | 24 | / | / |
| Color Zinc | Zn.C | 4-15 | 48 | / | / | |
| Nickel+tin plating | NiSn | 5-20 | 72 | 168 | 96 | |
| Nickel + Silver Plating | NiAg | 5-20 | 72 | 168 | 96 | |
| Nickel + Gold Plating | NiAu | 5-20 | 72 | 168 | 96 | |
| Nickel-Copper-Nickel+Tin Plating | NiCuNiSn | 5-20 | 72 | 168 | 96 | |
| Nickel + Electroless Nickel Plating (Hang Plating) | Ni+AP.Ni | 3-20 | 24 | 168 | 48 | |
| Nickel + Electroless Nickel Plating (Roller Plating) | Ni+AP.Ni | 3-20 | 24 | 168 | 48 | |
| Physical vapor deposition plating of aluminum | PVD.Ai | 2-15 | 24 | 168 | 24 | |
NdFeB magnets are most commonly used in galvanized and nickel plated, they have obvious differences in appearance, corrosion resistance, service life, price and so on:
Polishing difference:
nickel plating is superior to zinc plating in polishing, the appearance is brighter. High requirements for the appearance of the product will generally choose nickel-plated, while some of the magnets are not exposed, the appearance of the product requires a relatively low general galvanized.
Corrosion resistance difference:
zinc is active metal, can react with acid, so the corrosion resistance is poor; nickel-plated surface treatment, its corrosion resistance is higher.
Difference in service life:
Due to different corrosion resistance, the service life of zinc plating is lower than that of nickel plating, which is mainly manifested in the fact that the plating layer on the surface is easy to fall off after a long time of use, leading to the oxidation of the magnet, thus affecting the magnetic properties.
Hardness difference:
nickel plating is higher than zinc plating, in the process of use, you can greatly avoid the collision and other situations, making NdFeB powerful magnets appear to fall off the corner of the phenomenon, cracked, and so on.
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