1. What is a magnet coating?
Magnet coating is used to reduce the sensitivity of magnets to corrosion and other negative environmental factors that may cause magnet degradation. Strong magnet coating is similar to ordinary paint, but is mixed with small iron powder particles. Rare earth magnetic coating materials include nickel, copper, chromium, gold, black zinc, epoxy resin, etc. The coating of the magnet is very thin, so it has almost no effect on the magnetic properties of the magnet itself.
2. Why and when do magnets require coating?
The surface treatment of Nd-Fe-B is not to improve its performance. The coating on the surface of Neodymium magnet mainly plays a protective role. Neodymium iron boron strong magnets without surface coatings are prone to react with oxygen in the air and rapidly oxidize. Therefore, to prevent this from happening, we usually undergo electroplating treatment. And the appearance of the strong magnet after electroplating treatment is more beautiful.
3. What are the common magnetic coatings on the market?
There are many different magnet coatings for sintered Neodymium magnet, but the appropriate coating will depend on the application parameters, as well as many other factors such as environment, temperature, durability, etc.
Common plating:
1. Nickel
Nickel is the most common coating on powerful magnets. Nowadays, it is generally plated with three layers, namely nickel copper nickel. It can protect rare earth magnets from fragmentation and corrosion in the 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 bright appearance similar to the color of stainless steel. It has a thickness of 15-25 um and a working temperature of approximately 200 ° C.
The main application areas of nickel plated neodymium iron boron magnetic coatings are motors, medical devices, generators, pumps, sensors, automobiles, and several other industries.
2. Zinc
Zinc coating provides good adhesion, and you can pay attention to the magnets in the motor. Many of them are galvanized coatings, which are used to protect the magnets from corrosion in the surrounding air and provide mild moisture, water, or salt water protection. 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 approximately 120 ° C. Zinc coatings are mainly used for low-temperature applications and areas that require some protective barriers.
3. Epoxy resin
Unlike gold, zinc, and nickel, epoxy magnet coatings can serve as excellent barriers to salt, ambient air, water, or moisture. But it is slightly more expensive than the first three alternatives. Although it is easy to scratch and has a thickness of 15-30 um, it has good adhesion to steel with magnetic adhesive. Epoxy coatings are mainly used in the industries of ships, motors, sensors, automobiles, and consumer goods.
4. Gold plating
The gold-plated coating is used as an FDA approved medical coating for in vivo use, as a base coating for Ni Cu Ni. Like nickel coatings, it helps protect magnets from corrosion in the ambient air, but can also provide mild moisture, water, or salt water protection. The thickness of gold is very thin (about 0.1-1um), so its performance in salt spray testing may be poor, as most gold coatings are designed for thinness. Its maximum operating temperature is approximately 200 ° C.
5. Injection molding/plastic
This coating requires molds and tools. It is an excellent protective layer for rare earth magnets, which can prevent damage, impact, and corrosion. Can be used for coating medium to large magnets. Please note that small magnets cannot be coated with plastic. They can serve as good protective coatings against salt water, moisture, or water.
The color of plastic can be dyed into almost any color. The common thickness of the coating is between 1 and 2 millimeters. The maximum operating temperature usually depends on the type of ABS plastic selected. It is used for healthcare, education, consumer goods, etc.
Summary:
The coating of neodymium iron boron strong magnets mainly serves two purposes: to protect the magnet and to have a beautiful appearance. However, the magnetic performance of the magnet cannot be changed, which will improve its durability. Common coatings: nickel plating, zinc plating, gold plating, epoxy resin, injection molding/plastic, and of course, there are other coatings. We will gradually introduce them to you later.
