Abstract
Corrosion characters of Nd-Fe-B-sintered magnets in remanence states in sulfuric acid (H2SO4), phosphoric acid (H3PO4), sodium hydroxide (NaOH), and sodium chloride (NaCl) solutions have been investigated, respectively. Experimentally, the study was carried out with weight-loss and electrochemical potentiodynamic polarization tests. As the results showed, electrochemical reaction mechanism of Nd-Fe-B-sintered magnets in different solutions was not changed by the remanence state. But, corrosion of the magnets was accelerated in H2SO4 and NaCl solutions, owing to the formation of an occluded corrosion cell with self-catalyzing effect. In H3PO4 and NaOH solutions, however, Nd-Fe-B-sintered magnets were passivated and corrosion was decelerated. The remanence state changed the electric double-layer structure on the magnet/electrolyte interface, which was responsible for the production of the magneto overpotential and the change of electrochemical corrosion rate of Nd-Fe-B-sintered magnets.
