Electrochemical reduction and re‐oxidation behavior of α, β, and γ‐iron oxy‐hydroxide films on electrodes

Abstract

To clarify the effect of rust on the corrosion of steel exposed to an atmosphere containing chloride, the electrochemical reduction and re‐oxidation behavior of α, β, and γ‐FeOOH is studied. Films are formed on gold electrodes and are electrochemically reduced at several potentials, thus simulating the corrosion potential under wet and dry conditions. The current flowing through the β‐FeOOH is the highest among the three films. The β‐FeOOH is reduced to Fe3−δO4 at a noble potential of less than −300 mV, relative to a standard hydrogen electrode (SHE) and is reductively dissolved to Fe2+ at a noble potential of less than −100 mV (SHE). The formed Fe3−δO4 is not reformed to β‐FeOOH during re‐oxidation. It is found that the β‐FeOOH plays an important role in the cathodic reaction, acting as an oxidant, and can significantly affect the corrosion of steel in the atmosphere.

Effect of Nickel Addition on the Corrosion Resistance of Steel in a Subtropical Seashore Environment

“…The electrochemical reduction characteristics of rust formed on carbon steel and 5% Ni steel were examined using potentiostatic measurements at a potential of -600 mV vs. SSE to selectively reduce β-FeOOH and γ-FeOOH. 16,17) The results are shown in Fig. 9.…”

“…Polarization measurements were performed at a scan rate of 20 mV/min, and potentiostatic measurements of rust reduction were also performed in the same electrolyte. A potential of -600 mV vs. SSE was applied following Doi et al 16) and Sugae et al 17) to selectively reduce βand γ-FeOOH but not α-FeOOH.…”