Nd-Fe-B permanent magnet (king of magnets) is widely used in different technical fields with broad application prospects, for comparing to other magnet material, neodymium magnet has higher remanence, magnetic coercivity and the best magnetic energy product.
While the neodymium-Iron-Boron magnet has a wide range of applications with its excellent magnetic properties and low cost, its poor corrosion resistance is a major drawback.
Under static immersion experiment at room temperature, corrosion speed of neodymium samples is measured 0.188g/m2.h in 3% sodium chloride solution, while the corrosion rate of carbon steel 0.119g/m2.h.
Meanwhile, electrochemical performance experiment result proves that neodymium permanent magnets are more susceptible to corrosion than carbon steel, but the electrochemical properties of both are similar to a certain degree.
Many of the scholars and researchers at home and abroad believe that Nd-Fe-B is a powder metallurgy products. Because of the difference between Nd phase, boron-rich phase, neodymium-Iron-Boron potentials, corrosion of Nd-Fe-b is mainly reflected as intergranular corrosion based on electrochemistry. Therefore, it is an eternal theme to ensure that the Neo magnets are not affected by corrosion and ensure that the magnetic properties of Nd-Fe-B magnet do not loss.
Corrosion of Nd-Fe-B permanent magnet is mainly dealt with by plating of nickel, zinc, phosphate, epoxy and others are the main solutions to problem of Corrosion problem. But blackening phenomenon of neodymium-Iron-Boron is seldom seen in reports. Hereby we will discuss black conversion film for NdFeB magnets based on the mechanism of iron and steel blackening.
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