The effect of gallium addition on the corrosion resistance of a Pr-Fe-Co-B-Nb permanent magnet alloy

Abstract

The effect of gallium addition (0.5 wt. %) on the corrosion resistance of a Pr-FeCo-B-Nb permanent magnet alloy has been investigated. The electrochemical behavior was assessed using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The electrochemical tests were carried out during 30 days using a naturally aerated 0.02M Na2HPO4 solution at room temperature as electrolyte. The specimens were annealed for 20h at 1100ºC prior to immersion in the electrolyte. The results pointed towards a beneficial effect of Ga addition on the resistance of the surface film to breakdown. The surface film was formed upon immersion in the phosphate solution used as test medium. In this solution, the corrosion resistance of both alloys tested, either with or without Ga, increased with time of immersion due to the continuous growth of the phosphate film on their surfaces.

The effect of gallium addition (0.5 wt. %) on the corrosion resistance of a Pr-FeCo-B-Nb permanent magnet alloy has been investigated. The electrochemical behavior was assessed using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The electrochemical tests were carried out during 30 days using a naturally aerated 0.02M Na2HPO4 solution at room temperature as electrolyte. The specimens were annealed for 20h at 1100ºC prior to immersion in the electrolyte. The results pointed towards a beneficial effect of Ga addition on the resistance of the surface film to breakdown. The surface film was formed upon immersion in the phosphate solution used as test medium. In this solution, the corrosion resistance of both alloys tested, either with or without Ga, increased with time of immersion due to the continuous growth of the phosphate film on their surfaces.