The parallel plate avalanche counter (PPAC) built in our laboratory was used to measure the CEM spectra of iron electrodeposited over a steel substrate. The electron counter was operated with ketone gas inside the ionization chamber, at a pressure of 34 torr, and an applied voltage of 650V, with the purpose of showing the depth profile of CEM spectra. These spectra were measured by selecting the energy range of reemitted electrons. It was demonstrated that the PPAC in this configuration can be used to identify the chemical species formed at different depths from the resonator surface. This method was applied to the oxidation of iron in two different environments.