Kinetics study of ozone gas enhanced passivation of pure iron

Active Members of Electrochemical Society Passive film was exposed by ozone gas to study the applicability of improving the surface structure such as atomically flat terrace. Because water and/or other minor species were contained in the passive oxide film, it is expected that ozone gas oxidized some of them and help the reconstruction of passive film toward stable crystal phase of oxides. The oxide film thickness increased much faster in ozone gas than in air due to ozone oxidation. The thickness increased remarkably by passivation at 800 mV (Ag/AgCl), but increased slightly in ozone gas and decreased in air due to reconstruction after rapid growth of oxides by the passivation at 800 mV. The thickness decreased by passivation at -350 mV, but increased apparently by ozone exposure. The widest terrace width was obtained by passivation at 800 mV and the subsequent ozone gas exposure. The value was three times larger than that of air-formed oxide film. The terrace width with atomic scale flatness correlated with the corrosion resistance except for the increase in oxides film thickness.