Comparison of the corrosion behavior of die-upset and sintered NdFeB magnets

Author

Ma, B.M. ; Lee, D. ; Smith, B. ; Gaiffi, S. ; Owens, B. ; Bie, H. ; Warren, G.W.

Author_Institution

Magnequench Technol. Centre, Research Triangle Park, NC, USA

Volume

37

Issue

4

fYear

2001

fDate

7/1/2001 12:00:00 AM

Firstpage

2477

Lastpage

2479

Abstract

Corrosion rates for sintered NdFeB magnets are compared with NdFeB magnets prepared from melt spun material (hot pressed and die upset). Corrosion rates were determined by standard electrochemical methods in 0.9 M Na₂SO₄, at pH 2.4 and 4.4. Autoclave tests correlated quite well with corrosion rates measured electrochemically in the more aggressive pH electrolyte. The more aggressive pH 2.4 electrolyte is more representative of the conditions occurring in the autoclave tests. The hot pressed and die upset magnets exhibit significantly lower corrosion rates than sintered magnets. The reduction in corrosion rate is probably due to smaller grain size and diminished amounts of Nd-rich material

Keywords

boron alloys; corrosion; ferromagnetic materials; grain size; hot pressing; iron alloys; melt spinning; neodymium alloys; permanent magnets; sintering; NdFeB; NdFeB sintered magnet; autoclave test; die upset; electrochemical corrosion; electrolyte pH value; grain size; hot pressing; melt spinning; potentiodynamic polarization; Composite materials; Corrosion; Grain boundaries; Grain size; Iron; Magnetic materials; Magnets; Materials testing; Neodymium; Pressing;

fLanguage

English

Journal_Title

Magnetics, IEEE Transactions on

Publisher

ieee

ISSN

0018-9464

Type

jour

DOI

10.1109/20.951208

Filename

951208