Investigation on the corrosion resistance of Nd-Fe-B magnets used in dentistry coated with phosphate conversion and silane coatings

Abstract

The aim of this work is to evaluate the effectiveness of corrosion protection due to two different surface treatments: a phosphate conversion and a nonfunctional silane (BTSE) layer on commercial sintered Nd-Fe-B magnets used in dentistry by electrochemical methods. The electrochemical tests were performed in a phosphate buffered solution (PBS) at neutral pH. The corrosion behavior was monitored by means of electrochemical impedance spectroscopy (EIS) and anodic potentiodynamic polarization curves. Scanning electron microscopy and Energydispersive spectroscopy (SEM-EDS) analyses were used to monitor coating deposition. The results indicated a good performance of the phosphate layer, whereas the BTSE layer did not improve the corrosion resistance of the magnets. Impedance results evidenced the occurrence of diffusion-controlled phenomenon, likely linked to the presence of pores in the magnet microstructure.