What is a magnet coating? What is the role of strong magnet coating?

The magnet coating is used to reduce the sensitivity of the magnet to corrosion and other negative environmental factors that may degrade the magnet. The strong magnet coating is similar to ordinary paint, except that tiny particles of iron powder are mixed in. Rare earth magnetic coating materials include nickel, copper, chromium, gold, black zinc, epoxy resin and so on. The coating of the magnet is so thin that it has almost no effect on the magnetic properties of the magnet itself.

A, what is the magnet coating?

The magnet coating is used to reduce the sensitivity of the magnet to corrosion and other negative environmental factors that may degrade the magnet. The strong magnet coating is similar to ordinary paint, except that tiny particles of iron powder are mixed in. Rare earth magnetic coating materials include nickel, copper, chromium, gold, black zinc, epoxy resin and so on. The coating of the magnet is so thin that it has almost no effect on the magnetic properties of the magnet itself.

B,Why and when do magnets need to be coated?

Ndfeb surface treatment is not to improve its performance, neodymium magnet surface coating mainly plays a protective role. 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 electroplated after the strong magnet appearance more beautiful.

C, what are the common magnet coating 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, etc.
Common coating:

1. The nickel

Nickel is the most common coating on powerful magnets. It is now commonly plated in three layers, namely nickel - copper - nickel. It protects rare earth magnets from fragmentation and corrosion in ambient air. However, it should not 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 an operating temperature of about 200°C.
The main application fields of nickel-plated NdFeb magnet coating are motor, medical instrument, generator, pump, sensor, automobile, and other industries

2. The zinc

Zinc coating provides good adhesion, you can look at the magnets in the motor, many are galvanized coating, it is used to protect the magnet from corrosion in the surrounding air, and to provide mild protection from moisture, water or salt water. However, if the magnet is in a humid environment, it is not a suitable choice. Its thickness is 4-10 um and its maximum operating temperature is about 120°C. Zinc coating is mainly used for low temperature applications and where a little protective barrier is needed.

3. Epoxy resin

Unlike gold, zinc and nickel, epoxy magnet coatings can act as excellent barriers to salt, ambient air, water or moisture. But it is 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, motor, sensor, automotive and consumer goods industries.

4.Gold-plated

The gold-coated coating is used as an FDA-approved medical coating for in vivo use, and it is used as a base coating for Ni-Cu-Ni. Like the nickel coating, it helps protect the magnet from corrosion in ambient air, but can also provide mild protection against moisture, water, or saltwater. The thickness of gold is very thin (about 0.1-1um), so it may perform poorly in salt spray tests because most gold coatings are made to be thin. Its maximum operating temperature is about 200°C.

5. Injection molding/plastic

This coating requires molds and tools. It is an excellent protective layer for rare earth magnets against breakage, impact and corrosion. It can be used for coating of medium and large magnet. Please note that small magnets cannot be coated with plastic. They serve as a good protective coating against saltwater, moisture, or water.
Plastic can be dyed 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 in healthcare, education, consumer goods, etc.

Conclusion:

The coating of NdFeb strong magnet has two main functions: to protect the magnet and to have a beautiful appearance. But can not change the magnetic properties of the magnet, will improve the durability. Common coatings: Nickel, zinc, gold, EPOXY, injection/plastic, and of course others.