日本金属学会誌

J. Japan Inst. Metals, Vol. 49, No. 3 (1985),
pp. 217-223

Effects of Additive Ru on the Corrosion Resistance of Magnetic Fe Powders

Seiichi Asada1 and Masahiro Kitada1

1Central Research Laboratory, Hitachi Ltd., Kokubunji

Abstract:

The effects of additive Ru on the corrosion resistance of magnetic Fe powders are investigated. Fe and Fe-Ru powders are prepared from acicular fine α -FeOOH powder by hydrogen reduction. The corrosion resistance of the powders is evaluated by the saturation magnetization loss in a humid air atmosphere (333 K, 90% relative humidity). The coercivity, the saturation magnetization and the squareness ratio of Fe-5 at%Ru powder are similar to those of Fe powder. Moreover, the saturation magnetization loss of Fe-5 at%Ru powder is only one fourth of that of Fe powder, when these powders are exposed to the atmosphere for 540 ks (150 h).
To clarify the effects of additive Ru on the corrosion resistance, corroded and uncorroded sputtered Fe-Ru thin films are also investigated with Auger electron spectroscopy and anodic polarization technique. A Ru-enriched layer is formed by selective oxidation of Fe near the Fe-Ru thin film surface. The natural anodic potential of the alloy film increases slightly with an increase in Ru concentration. It is thought that these relate to the improvement of the Fe powder corrosion resistance by additive Ru.


(Received 1984/9/10)

Keywords:

iron powder, iron-ruthenium powder, corrosion resistance, coercivity, saturation magnetization, squareness ratio, sputtered thin film, Auger electron spectroscope, anodic polarization


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