Phosphate Coated Neodymium Magnet

Corrosion products on the metal surface have a certain protective effect which can hinder the contact between the metal matrix and the corrosive medium in the operating ambient. Such protective coating generated on metal matrix is commonly known as chemical conversion coating or conversion coating. Conversion coating could be generated either by spontaneously obtained in the natural environment or prepared under controlled. Unlike electroplating, electrophoresis, or organic coating process, conversion coating is the direct reaction products of metal matrix during pure chemical or electrochemical reaction. Phosphate coating is a common conversion coating which possess a long history. For sintered Neodymium magnet, phosphating process is referred to put magnets in the aqueous solution of dihydric phosphate and thus form a hydrated phosphate protective coating on surface. Phosphate coated Neodymium magnet is typically grey or dark grey. Phosphate coating has a porous structure and also insoluble in water, therefore, it can modify hygroscopicity and corrosion resistance of sintered Neodymium magnet and able to tackle short-term corrosion resistance demand and specific applications with low protective requirements. Phosphate coated Neodymium magnet can be classified to room temperature, middle temperature, and high-temperature type. Room temperature phosphate coating shows poor corrosion and moisture resistance. Middle temperature phosphate coating has moderate corrosion resistance and suitable for rust protection or priming. High temperature phosphate coating exhibit better corrosion resistance, heat resistance, binding force, and hardness in comparison with the first two options.

Phosphate Coated Neodymium Magnet-1