Corrosion behavior of NdFeB sintered magnets in HNO3-HF acid mixture solution

Corrosion behavior of NdFeB magnet in HNO3-HF solutions was investigated using open circuit potential and polarization measurements and impedance technique. Results showed that the additions of HF increased open circuit potential, corrosion potential and film/inductive/charge transfer resistance, but decreased corrosion current density of magnet. The HF effects on the corrosion performance were closely related to the formation of NdF3 corrosion products on magnet surface, in turn which depended on its content. Also the corrosion mechanism of magnet was discussed on the basis of structural observation, composition and EIS analyses.