Effect of cathodic pretreatment on the passivation of iron in neutral solution

Abstract

Pure iron specimens anodically oxidized at +600 mV ( vs sce) for one minute were partially reduced with a cathodic current of 10 μA/cm 2 and then reoxidized at the same potential for one hour. The experiment was performed in a boric acid/borate buffer solution at pH = 8.43 at room temperature. Variation in the thickness of the oxide film during the experiment is discussed for an inner Fe 3O 4 and outer γ-Fe 2O 3 layers, with emphasis on the effect of cathodic treatment. In the discussion, the amounts of charges for anodic and cathodic processes and the amount of dissolved Fe 2+ ions during the cathodic reduction are utilized.