The effect of aeration on the corrosion process of magnetized Nd-Fe-B magnets
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2004
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INTERNATIONAL WORKSHOP ON HIGH PERFORMANCE MAGNETS AND THEIR APPLICATIONS, 18th
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Resumo
The effects of aeration upon the corrosion process of magnetized Nd-Fe-B based sintered magnets
have been studied. The tests were carried out in naturally aerated and in deaerated 3.5 (wt.%)
sodium chloride solutions at various testing times by electrochemical impedance spectroscopy (EIS)
and potentiodynamic polarization methods. In deaerated solution the magnets exhibit higher
impedance values (one order of magnitude) than in aerated one. Bode phase angle diagrams
obtained in the former solution presented a single broad time constant, indicating the existence of a
single process in the investigated frequency range; moreover, the impedance behaviour was
maintained fairly constant from 5 days of immersion throughout the rest of the testing period. On
the other hand, the sample immersed in the aerated solution presented a constant and slow
diminution of the impedance all long the immersion time. In this case, Bode phase angle diagrams
presented a HF shoulder interpreted as the influence of the magnetic field on the transport of oxygen
to the interface. Larger icorr values and more noble potentials were also obtained for the magnet in
aerated solution. In the presence of oxygen, the corrosive attack penetrated deeply into the
specimens and, consequently, the magnetic properties diminished with immersion time. The
magnetic properties most influenced by corrosion were the remanence (Br) and the maximum
energy product (BHmax).
Como referenciar
OLIVEIRA, M.C.L.; FARIA JUNIOR, R.N.; ANGELO, J.D.; COSTA, I.; MELO, H.G. The effect of aeration on the corrosion process of magnetized Nd-Fe-B magnets. In: INTERNATIONAL WORKSHOP ON HIGH PERFORMANCE MAGNETS AND THEIR APPLICATIONS, 18th, 2004, Annecy, Franca. Proceedings... Disponível em: http://repositorio.ipen.br/handle/123456789/17515. Acesso em: 21 May 2024.
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