The new generation of supercritical cooled water reactors (SCWR) are susceptible to particulate fouling as a result of corrosion product sedimentation. Iron oxides are a major component of corrosion products and are also known to catalyze hydrogen peroxide decomposition. This work aimed to investigate the rate of H2O2 decomposition on the surface of a magnetite bulk electrode by using electrochemical impedance spectroscopy. A magnetite bulk electrode was immersed in a suspension of various concentrations of magnetite particles and initial H2O2 concentration of 10(-2) M. It was observed that the electrochemical response of the magnetite surface (which is partially oxidized to gamma - Fe+3 species) is a function of H2O2 concentration. Therefore, at different time intervals EIS was used to obtain charge transfer resistance as a proxy variable for hydrogen peroxide concentration. These measurements were compared to results obtained by permanganate titration. It was observed that the changes of decomposition current density extracted from the EIS data fitting process for various conditions were in good agreement with the titration results. H2O2 decomposition in the presence of iron oxide particles was found lobe a second-order reaction with rate constants of 0.015 and 0.017 min(-1) g(-1)L (obtained from EIS and titration methods, respectively). (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.003212jes] All rights reserved.