Effects of hydrogen peroxide on corrosion of stainless steel (II) ; Evaluation of oxide film properties by complex impedance measurement

A high temperature high pressure water loop, which can control H2O2 concentration with minimal oxygen (O2) coexistence, has been fabricated. In order to evaluate the effects of hydrogen peroxide (H2O2) on intergranular stress corrosion cracking. Not only static responses, i.e., electrochemical corrosion potential (ECP), of the stainless steel specimens exposed to H2O2 and O2 at elevated temperatures but also their dynamic responses, i.e., frequency dependent complex impedances (FDCI), were measured. The conclusions obtained by the experiments are as follows. 1. The ECP measured for the SUS 304 specimen exposed to 100ppb H2O2 reached the saturated level in 50h, showed a larger value than the specimen exposed to 200 ppb O2 and kept the same ECP level when the H2O2 concentration was decreased to 10ppb. 2. The FDCI measured for the specimen exposed to 100 ppb H2O2 showed saturation in the low frequency semicircles; this behavior was determined by the electric resistance of the oxide film and caused by saturat...