The effects of hydrogen and applied tensile stress on the passivity of type 304 stainless steel were investigated in borate buffer solutions containing chloride ions. Hydrogen was cathodically charged into specimens by applying a cathodic constant current density. Applied tensile stress is found to have no obvious effect on the breakdown potential of uncharged specimens unless the concentration of chloride ions in the borate buffer solution is high. Hydrogen significantly decreases the breakdown potential. For charged specimens at various tensile stress levels, breakdown potentials are well fitted as a function of charging current density using the second-order exponential decay equation. At a certain charging current density, the breakdown potential and applied tensile stress approximately follow a linear relationship. The slope of the straight line becomes more negative in the intermediate charging current density range than in both low and high current density ranges, indicating that tensile stress has a more obvious promoting effect on the breakdown of passive films formed on specimens charged in this current density range. It was observed that hydrogen increases the anodic current density in the passive range. Applied tensile stress affects the anodic current density in various degrees for the specimens charged at different charging current densities. (C) 2003 The Electrochemical Society.