AN ELECTROCHEMICAL INVESTIGATION OF DISSOLUTION OF ND-FE-B MAGNETS IN ACID-SOLUTION UNDER CATHODIC POLARIZATION

The effect of cathodic polarization, pH value of sulphate solution and stirring rate on the kinetics of dissolution of Nd15Fe77B8 magnets in magnetized and demagnetized states have been studied. With the increase of cathodic polarization the rate of dissolution increases. The reason for this abnormal dissolution is hydrogenation and mechanical degradation of the magnet surface. The abnormal dissolution rate increases linearly with the square root of the H2 evolution current density. Nd-Fe-B magnets in the magnetized state, as compared to demagnetized one, undergo lower abnormal dissolution. Independently of magnetization state the surface of the magnets deteriorates strongly after the cathodic exposure.