Anodic behaviour of iron in alkaline solutions

Abstract

Galvanostatic experiments have been made on iron electrodes in hydrogen-poor and hydrogen-saturated alkaline solutions at 20°C. Emphasis was on the active behaviour of iron, but attention was also paid to its passivation.The mechanism of the anodic dissolution of active iron is found to be the same in alkaline as in acid solutions. It is characterized by the dissolution reaction showing a first-order hydroxyl ion dependence and a V/ln i slope of RT/2F. The hydrogen electrode on active iron is found to have a pH-independent cathodic reaction of slope −2RT/F and a second-order hydroxyl ion dependent anodic reaction of slope 2RT/3F (when activation controlled). The passivation curves show clear inflections in the vicinity of the reversible FeO/Fe2O3 and Fe3O4/Fe2O3 potentials.A special discussion is given of the active dissolution reaction on the basis both of the present and of previous results.