NdFeB magnets are susceptible to corrosion. The 'Fe' in the name stands for Iron, and it rusts! Many of our magnets come with a Nickel, Zinc, Gold or Epoxy coating to protect them from moisture. If the coating is damaged (frequently the case with surplus magnets) the magnet could rust if exposed to water or humidity. If this is a concern to you, you can easily add another layer of protection by dipping the magnet in epoxy or plastic coating.