The effects of dissolved oxygen, hydrogen, and hydrogen peroxide on the corrosion (electrochemical) potentials (ECPs) of type 304 SS and alloy 182 in simulated boiling water reactor (BWR) coolant environments under various water chemistry conditions at 288°C are reported. In oxygenated systems, the measured ECP fell within the range +20 to −600 mV (vs SHE) depending on the O2 concentration. The effect of water flow rate on the ECP was also studied as function of dissolved O2 concentration. Increasing flow rate at constant oxygen concentration increased the ECPs of type 304 SS and alloy 182. The effect of hydrogen peroxide (H2O2) on the ECP of type 304 SS and alloy 182 in pure water was also determined. The authors found that the concentration of oxygen and the ECP increased immediately when H2O2 was injected into the cell. The measured corrosion potentials of both alloys were 200 to 400 mV more positive than for dissolved O2 at similar levels. However, the ECP was lower than that expected theoretically from a mixed potential model (COREPOTENTIAL), which we attribute to thermal decomposition of H2O2. The ECPs of type 304 SS and alloy 182 in water containing various O2/H2/H2O2 combinations were measured and compared with theoretical data from COREPOTENTIAL. The ECPs were lower than expected due to decomposition of H2O2 in the high-temperature environment. Finally, the difference between the ECP of type 304 SS and alloy 182 was negligible (normally < ± 20 mV) under all conditions.