Neodymium is easy to react to oxygen and oxidizes quickly if untreated. That's why all neodymium magnets are covered with a protective coating, which is so thin that it doesn't have any impact on the adhesive force of the magnet. Here are some common options to choose from. 

How to choose the suitable platings? 
Depending on the coating, the color of the magnet surface will be different, the corrosion resistance will be different, and the service life will also vary. Therefore, when buying a magnet, you can choose different coatings according to the working environment of the magnet. If the working environment of the neodymium magnet is harsh, you can choose the coatings that are more resistant to corrosion, such as polymer materials and epoxy resins, and vice versa.