Effect of pH, temperature, and H2O2 on the electrochemical oxidation behavior of iron in perchlorate solutions

Abstract

The effects of pH, temperature, and H2O2 on the electrochemical oxidation behavior of iron were determined in perchlorate solutions. Iron exhibited four distinct oxidation behaviors in perchlorate solutions that had a pH of 3.0. First, the active dissolution potential with two current waves was observed in the range of −0.7 to 0 V. Second, the range of stable passivation was observed between 0 and 0.3 V. Third, unstable passivation was observed in the range of 0.3 to 1.2 V. Finally, pitting corrosion was observed at a potential above 1.2 V. The increase in pH stabilized the passivation of iron, whereas the increase in temperature had a negative influence on both the passivation and pitting behaviors of iron. The presence of H2O2 at concentrations less than 1.45 mM had an adverse effect on the formation of the passive oxide layer. However, H2O2 at concentrations greater than 1.45 mM exerted a beneficial influence on the formation of stable iron oxide in the active dissolution region. In addition, H2O2 mitigated the pitting corrosion of iron regardless of the H2O2 concentration.