The effect of the presence of dissolved ferrous ion (Fe2+(aq)) on surface oxide film growth and conversion on carbon steel in pH 8.4 borate solutions was studied as a function of potential. The results of electrochemical measurements and surface analyses provide a consistent picture of oxide growth and conversion behaviour and the role of Fe2+(aq) on the oxidation. At potentials < -0.4 V-SCE the presence of Fe2+(aq) in solution somewhat suppresses the dissolution of Fe-II, thus reducing the net rate of anodic oxidation, while at potentials > -0.4 V-SCE the presence of Fe2+(aq) at 0.1 mM can substantially increase the rate of formation of gamma-FeOOH on the carbon steel surface via oxidation of Fe2+(aq). (C) 2012 Elsevier Ltd. All rights reserved.