Initial Stages of the Anodic Oxidation of Iron in Chloride Solutions

Data have been obtained for the rate of reaction of freshly generated iron surfaces at low potentials with aqueous solutions containing chloride ions. The presence of chloride ions accelerates the formation of the first monolayer of oxidized iron, but with no significant increase in the charge required to form it. The data are interpreted in terms of parallel reaction paths involving water and chloride, respectively, the latter path having a rate constant some one hundred times that of the water path. The first oxidized monolayer on the iron surface consequently contains both Cl⁻ and OH⁻. No evidence was obtained for dissolution directly from the bare metal surface prior to monolayer formation.