1. What is magnet coating?
Magnet coatings are used to reduce the magnet's susceptibility to corrosion and other negative environmental factors that can degrade magnets. Strong magnet coatings are similar to regular paint, but with tiny particles of iron powder mixed in. Rare earth magnetic coating materials include nickel, copper, chromium, gold, black zinc, epoxy resin, etc. The magnet coating is very thin, so it has almost no effect on the magnetic properties of the magnet itself.
2. Why and when do magnets need coating?
The NdFeB surface treatment is not to improve its performance, the surface coating of the NdFeB magnet is mainly for protection. NdFeB strong magnets without surface coating are easy to react with oxygen in the air and oxidize rapidly, so in order to prevent this from happening, we usually carry out electroplating treatment. And the appearance of the strong magnet after electroplating is more beautiful.
3. What are the common magnet coatings on the market?
There are many different magnet coatings for sintered neodymium magnets, but the appropriate coating will depend on the parameters of the application, as well as many other factors such as environment, temperature, durability, and more.
4. Common coating:
nickel:
Nickel is the most common coating on powerful magnets. Now generally three layers are plated, namely nickel-copper-nickel. It protects rare earth magnets from chipping and corrosion in ambient air. However, it cannot be used as a protective coating against moisture, water or salt water. Nickel coating is also a decorative finish, with a glossy finish similar to stainless steel. It has a thickness of 15-25 um and an operating temperature of about 200°C.
The main application areas of nickel-plated NdFeB magnet coatings are motors, medical devices, generators, pumps, sensors, automobiles, etc., as well as several other industries.
Zinc:
Zinc coating provides good adhesion, you can keep an eye on the magnets in the motor, many are galvanized coatings, it is used to protect the magnets from corrosion in the surrounding air and provides mild protection against moisture, water or salt water . However, if the magnet is in a humid environment, it is not a suitable choice. It has a thickness of 4-10 um and a maximum operating temperature of about 120°C. Zinc coatings are mainly used in low temperature applications and where a little protective barrier is required.
Epoxy resin:
Unlike gold, zinc and nickel, epoxy magnet coatings act as an excellent barrier to salt, ambient air, water or moisture. But it's slightly more expensive than the first three alternatives. Although it scratches easily and is 15-30 um thick, it has good adhesion to steel with magnetic glue. Epoxy coatings are mainly used in the marine, electrical, sensor, automotive and consumer goods industries.
Gold plating:
Gold-plated coatings are used as FDA-approved medical coatings for in vivo use, and it is used as an undercoat for Ni-Cu-Ni. Like the nickel coating, it helps protect the magnets from corrosion in the ambient air, but can also provide mild protection from moisture, water or salt water. Gold is thin (about 0.1-1um) so it may perform poorly in salt spray tests as most gold coatings are made to be thin. Its maximum operating temperature is about 200°C.
Injection/Plastic:
Dies and tools are required for this coating. It is an excellent protective layer for rare earth magnets against breakage, shock and corrosion. It can be used for the coating of medium and large magnets. Note that small magnets cannot be coated with plastic. They act as a good protective coating against salt water, moisture or water.
The color of plastic can be dyed almost any color. Common thicknesses of coatings are between 1 and 2 mm. The maximum operating temperature usually depends on the type of ABS plastic selected. It is used in healthcare, education, consumer products, etc.
5.Summarize:
The coating of NdFeB strong magnet has two main functions: protecting the magnet and beautiful appearance. However, the magnetic properties of the magnet cannot be changed, and the durability will be improved. Common coatings: nickel-plated, zinc-plated, gold-plated, epoxy resin, injection molding/plastic, and of course other coatings. GME supports customization. ODM&OEM are welcome.