Corrosion assessment of Nd–Fe–B alloy with Co addition through impedance measurements

• Published in: Journal of alloys and compounds Vol. 408; pp. 1373 - 1376
• Main Authors: Sunada, Satoshi, Majima, Kazuhiko, Akasofu, Yasuhiro, Kaneko, Yuji
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2006
• Subjects: Charge transfer resistance; Corrosion resistance; Immersion test; Nd-Fe-B magnet; Nyquist plot; Corrosion resistance; Immersion test; Nyquist plot; Charge transfer resistance; Nd-Fe-B magnet
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2005.04.039

Effect of Co addition on improving the corrosion resistance of Nd 11.8Fe 82.3− x Co x B 5.9 specimens with different x ( x = 0, 2.5, 5.0, 7.5, 10.0) have been investigated through the electrochemical method including the impedance measurement. With increasing amount of Co content the natural electrode potential shifted to nobler side. The Nyquist plot showing a semi circle in which frequency increases in counter clockwise direction was obtained. From the result it was clarified that the diameter of the semi circle corresponding to the charge transfer resistance, R ct, became larger with increasing Co content, which indicates the improvement of the corrosion resistance for the Nd 11.8Fe 82.3− x Co x B 5.9 specimens by Co addition because the R ct is inversely proportional to the corrosion rate. Judging from these results it is suggested that the impedance measurement is one of the effective methods to obtain the information of corrosion behavior for the Nd 11.8Fe 82.3− x Co x B 5.9 specimens.