Rare earth permanent magnet NdFeB (Neodymium-Iron-Boron) is a new kind of magnetic material developed in the 1980's with excellent magnetic characteristics (high energy product and high coercive force etc.) and relatively low cost. It is getting to replace the traditional magnets of hard ferrite, AlNiCo and SmCo in many fields such as electro-accoustic devices, electric motors, sensors/transducers, instruments and meters, auto industry, petro-chemical industry and magnetic health-care products etc. NdFeB magnets are very powerful. They have a higher Maximum Energy Product, (BH)max, than SmCo magnets. (BH)max of NdFeB can easily reach 30 MGOe and even goes up to 52 MGOe. NdFeB magnets can replace SmCo magnets in most cases, especially where operating temperature is less than 80°C. The temperature stability of NdFeB is not as good as SmCo magnets. Magnetic performance of NdFeB magnets will deteriorate rapidly above 200°C. Compared to SmCo magnets, the corrosion and oxidation resistance of NdFeB is relatively low. Therefore, A surface coating is usually applied on NdFeB magnets. Zinc or nickel coating is common used as a protective layer. Other materials such as gold, brass, tin or polymer (epoxy) are also used for this purpose.