The effect of absorbed hydrogen on the corrosion behavior of sintered NdFeB magnet

Abstract

The absorption of hydrogen by NdFeB magnet has been investigated by using the electrochemical charging technique at constant cathodic current density Ic ranging from 0 to 4 mA/cm2. Open circuit potential measurements (OCP) and polarization curves were carried out to study the corrosion behavior of the charged NdFeB magnet in 0.01 mol/L NaCl solution. The results showed that hydrogen had a strong influence on the corrosion of NdFeB magnet. The open circuit potential became gradually negative due to the hydrogen incorporation into the NdFeB magnet. The corrosion resistance was reduced gradually with the increasing cathodic current density Ic. The surface structure and the morphology of the charged NdFeB magnet were examined by XRD and SEM. The results revealed that the effect of the absorbed hydrogen focused mostly on accelerating the exfoliation corrosion of Nd2Fe14B matrix grain.

Magnetic Materials: Novel Monitors of Long-Term Evolution of Engineered Barrier Systems

“…Reacted Nd-Fe-B magnets scatter along a clear trend from the PSD field into the multi-domain (MD) field. Corrosion in this magnet type leads to the formation of a complex mixture of fine grained Nd-Fe-B hydrides around unreacted Nd-Fe-B [24][25][26][27], which leads to a net superparamagnetic behaviour ( Figure 3) and precipitation of Nd and Fe oxyhydroxides adjacent to the corroded magnets. This produces the drastic decrease of the main hysteresis parameters observed in Figure 8, marking the transition from a magnetocrystalline-single-domain (SD) material to a superparamagnetic material (MD) with increasing corrosion from the unreacted magnet to the reacted alloy.…”

Corrosion resistance of the NdFeB coated with AlN/SiC bilayer thin films by magnetron sputtering under different environments

“…Magnetic sputtering coating technique is the low temperature and friendly environment, so it can replace the electroplating for preparing NdFeB protective coating. Al, Ti/Al and Ni/Al coatings have been deposited on NdFeB by thermal evaporation [12,13], however, it has not been reported that AlN/SiC bilayer films are prepared on NdFeB by magnetron sputtering. AlN has the excellent mechanical properties and thermostability, and its lattice constant and thermal expansion coefficient are between the NdFeB and SiC, so it can improve the adhesion strength between the SiC film and the NdFeB substrate.…”