Thermodynamic stability of Cr2O3 point defects in aqueous environments is studied using density functional theory (DFT) calculations with varying electrolyte pH and electrode potential. In reducing conditions, the most stable defects are found to be oxygen vacancies, whereas in oxidizing conditions, chromium vacancies are favored. Moreover, oxygen vacancies are shown to form trapping sites for hydrogen and chloride ions. Consequences for the stability of passive films of stainless steels in acidic or chloride containing environments are delineated. Last, possible substitutions of Cr by Fe, Mo and Ni in Cr2O3 passive films are also investigated. (C) 2014 The Electrochemical Society. All rights reserved.