Corrosion Behavior of NdFeB Magnets in Different Aqueous Solutions

Sintered NdFeB magnets possess excellent magnetic properties, but behave passively in alkaline and saline media and are susceptible to corrosion in acidic environments. The corrosion behavior of NdFeB magnets in industrial environments: potassium hydroxide (KOH), perchloric acid (HClO₄) and sodium chloride (NaCl), was investigated by immersion and electrochemical tests. The immersion test concluded that the most corrosive electrolyte of the three studied was HClO₄. Electrochemical tests showed that the NdFeB sample without magnetic order had better corrosion resistance. Metallographic microscopy and scanning electron microscopy support the obtained corrosion data. X-ray photoelectron spectroscopy indicates that the main elements on the surface of the analyzed sample (Nd, Fe, B) are in the oxidized state after corrosion.

Keywords:
NdFeB magnets; corrosion; X-ray diffraction; scanning electron microscopy; energy dispersive X-ray analysis; X-ray photoelectron spectroscopy