Tritiated water contains radiolytic hydrogen peroxide. The corrosion potential of Inconel 690, as well as the redox potential of tritiated water, taken immediately from a closed storage vessel with a pressure of 9 10 5 Pa radiolytic gases, are in the passive-transpassive regions. After removal from storage, the concentration of tritiated hydrogen peroxide decreases and these potentials are in the passive region showing the importance of the concentration of radiolytic species on passivity and corrosion. Depending on passive potentials and tritiated hydrogen peroxide concentration, the passive oxide layer changes. The thickness increases with the passive potential, then decreases at higher passive potentials or tritiated hydrogen peroxide concentration.