Hydrogen Absorption by Co-Substituted Nd-Fe-B High Coercivity Magnetic Material

Abstract

The present paper aims at explanation of the advantageous role of partial substitution of iron by cobalt in Nd-Fe-B magnet for distinct inhibition of mechanically assisted corrosion phenomena. The hydrogen uptake by Nd16Fe76B8 and Nd16Fe56Co20B8 sintered materials have been compared with the use of charge/discharge method in terms of the alloys corrosion behavior in strong alkaline solution. For initial cycles, the hydrogen discharge capacity of Co-containing alloy is 5-10 times lower than that for the Nd16Fe76B8 reference alloy. After 6-7 cycles both alloys reveal comparable hydrogen capacity. Also the plots of polarization curves testify to comparable corrosion resistance for both materials. The unusual resistance of Nd16Fe56Co20B8 sinter to pulverization should be ascribed to strong inhibition of hydrogen absorption at initial steps of corrosion process.