Double Loop Electrochemical Potentiokinetic Reactivation testing has been employed to experimentally determine the degree of sensitization (DOS) of an austenitic stainless steel subjected to isothermal heat treatment for various times in the temperature range 700–820°C. For the different heat treatment conditions, the chromium concentration profiles across grain boundaries were calculated using the diffusion module in Thermo-Calc^® based on the assumptions that sensitization is caused by grain boundary M₂₃C₆ precipitates and that local multicomponent equilibrium and flux balance exist at the carbide - matrix interface. Comparison of the experimental DOS values and the details of the chromium concentration profiles was used to establish a quantitative depletion factor that predicts sensitization at short annealing times.