CORROSION-RESISTANCE OF THE FE-AL-C PERMANENT-MAGNET ALLOY

The correlation between corrosion behaviour rate of hard magnetic Fe-A I-C alloys and their microstructure and phase composition is presented . Potentiokinetic polarization curves of the tested material in acid ( pH = 1 and 2) and neutral (pH=7) sulphate solutions have been measured . For open-circuit condition, kinetic curves of etching of the samples in 0.5 M H2SO4 have been determined. The resistance of the tested mag nets against atmospheric corrosion has been evaluated using a salt-spr ay test. The atmospheric corrosion rate is 1.5-2 times slower than tha t found for Nd-Fe-B type magnets. The Fe-Al-C alloys show good corrosi on resistance in neutral environments and corrode at rates comparable to that of white cast-iron in acid environments. (C) 1998 Published by Elsevier Science Limited. All rights reserved.