SOME CORROSION ELECTROCHEMICAL PROPERTIES OF THE ND-FE-B TYPE MAGNETIC MATERIAL

1 LASEK Stanislav
Co-authors:
1 SKOTNICOVÁ Kateřina 2 BYRTUS Marek 2 HLINKA Josef
Institutions:
1 VŠB – Technical University of Ostrava, Faculty of Metallurgy and Materials Engineering, Regional Materials Science and Technology Centre, Av. 17. listopadu 15, 70833 Ostrava-Poruba, Czech Republic, e-mail: stanislav.lasek@vsb.cz
2 VŠB – Technical University of Ostrava, Faculty of Metallurgy and Materials Engineering, Department of Material Engineering, Av. 17. listopadu 15, 70833 Ostrava-Poruba, Czech Republic
Conference:
24th International Conference on Metallurgy and Materials, Hotel Voronez I, Brno, Czech Republic, EU, June 3rd - 5th 2015
Proceedings:
Proceedings 24th International Conference on Metallurgy and Materials
Pages:
1558-1564
ISBN:
978-80-87294-58-1
ISSN:
2694-9296
Published:
12th January 2015
Proceedings of the conference were published in Web of Science and Scopus.
Metrics:
329 views / 139 downloads
Abstract

Research in the field of magnetic materials based on Nd-Fe-B is focused on the improvement of certain magnetic characteristics by alloying of suitable elements (Co, Dy, Pr, Cu), extending the thermal stability of these permanent magnets, improving their corrosion resistance and the creation of nano-structure modifications. Magnets based on Nd-Fe-B are susceptible to corrosion, especially in humid atmospheres. The corrosion resistance of these magnets is a function of the structure, temperature, degree of environment humidity and Nd-rich phase reactivity. The paper is focused on determining and comparing the corrosion resistance of magnetic material NdPr-FeM-B (produced by powder metallurgy, M = Cu,Co,Al) in several environments. For comparative purposes, unalloyed carbon steel (C ≤ 0.1 wt.%) was tested under the same conditions. On the basis of electrochemical polarization measurements there were determined polarization curve, corrosion characteristics and parameters (corrosion potential, polarization resistance, pitting potentials, etc.) of mentioned selected materials in aqueous solutions (Na2SO4, NaH2PO4, NaCl). Salt spray test was also performed with these materials. The heterogeneous structure of magnetic material and uneven and/or localized corrosion was observed using microscopy. In the sodium chloride solution, a higher corrosion resistance reached steel in comparison with the magnet, in sodium sulfate solutions the results were not clear (depending on the pH, surface condition). The magnetic material exhibited a much higher resistance in the solution of NaH2PO4 in comparison with the corrosion resistance in other test solutions.

Keywords: magnetic material, Nd-Fe-B, corrosion resistance, polarization test

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