To better understand the phenomena in metal equipment corrosion in tritiated water, a study of the behavior of oxide layers on a cobalt-based stainless superalloy was made in this highly radioactive medium, The oxide characteristics are modified from the corrosion potential, in passivity and up to the passivity and transpassivity limits. The corrosion of oxide sublayers, as exfoliation of the oxide, was shown. This would appear to be due to diffusion of tritiated species in the oxide. These species accumulate at the oxide-alloy interface, thus modifying the number of charge carriers in the oxide.