J. Japan Inst. Metals, Vol. 28, No. 11 (1964),
pp. 684-688

Study on Anodic Behavior of Iron and Iron Oxides

Tatsuo Maekawa¹ and Nobuo Nakajima¹

Abstract:

Anodic behaviors of pure iron and its oxides in acid and alkaline solutions were investigated to clarify the significance of passivation potential and other oxidizing potential of iron. The anodic polarization curve of pure iron indicated four current peaks at the potentials of about -0.1, 0.3, 0.6 and 1.4 V in 1 N H₂SO₄, and -0.9, -0.8, -0.4 and 0∼0.4 V(vs S.C.E.) in 1 N KOH, respectively. The anodic polarization curves of FeO_1.05, FeO_1.1 and Fe₃O₄ indicated three, two and one peaks, respectively. And the potentials of the peaks of the oxides agreed with those of pure iron. From these anodic behaviors of oxides, it was suggested that the four potentials at the current peaks in the potential-current curve show four redox potentials of Fe/FeO_1.05, FeO_1.05/FeO_1.1, FeO_1.1/Fe₃O₄, and Fe₃O₄/Fe₂O₃. These potentials were also confirmed from the measurements of potential decay curves of iron and its oxides. It was concluded that the passivation potential of iron in 1 N H₂SO₄ solution corresponded with the redox potential of FeO_1.05/FeO_1.1, where as the passivation potential in 1 N KOH solution corresponded with the redox potential of Fe/FeO_1.05 or FeO_1.05/FeO_1.1.

(Received 1964/5/25)

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