The magnet are made of powder. It is fragile and easy to oxidation corrosion. If you do not do the surface coating for the magnet, the magnet will be rust in several days. It is easy to make the magnetic powder fall off. The magnetic energy will be reduced. So when you purchase the magnet, you need to consider the surface coating.
Normally the surface coatig is zinc coating, nickel coating, epoxy coating and gold plating.
- Zinc Coating: Low price, rust protection is not as good as nickel coating. It is suitable in dry inhouse environment. The thickness is about 8~15micron. The salt pray effect is not as good as the nickel coating.
- Nickel Coating: The rust protection effect is better than the zinc coating. The surface is bright. It is suitable in industrial environment. However, the nickel coating layer is soft. It is easy to scratch.
- Epoxy Coating: The corrosion resistance is high. It is suitable in the humid and chemical air environment, eg. food processing, water treatment. However, the thickness of the layer is about 30~100micron. It will slightly effect the space between the magnet and workpiece.
- Gold Plating: It will used in special electronics and precise instrument. The cost is high. We do not recomend to use in the industrial attraction environment.
If the thickness of the layer is more than 100 micron, it will increase the space of the magnet and workpice. That will result in the attraction force will reduced. However for some fixture which need high attraction force, we advice that the thickness of the layer should be within 20 micron. In the design, we need reserve the space to make up for the space.
The magnet is easy to chip or crack. When we install the magnet, we advice you to use the fixture to position. That could avoid the dirrectly crash. In the scenario of suffering shear force, we should design the mechanical limitation structure. It could make the magnet only suffering the normal force. It could avoid the magnet resistant lateral shifting by itself.
