The Pourbaix diagram for HP-13Cr stainless steel (SS) in the aggressive oilfield environment has been revised. Extrapolation of thermodynamics data to elevated temperatures has been performed with the revised model of Helgeson. The area of the corrosion of HP-13Cr SS and the pH value of environment have been calibrated on the Pourbaix diagram using electrochemical measurements and surface analysis. The results indicated that the quinary Pourbaix diagram (Fe-Cr-H2O-Cl--CO2) can be obtained by the overlap of three ternary Pourbaix diagrams, i.e., Fe-Cr-H2O, Fe-Cr-Cl- and Fe-Cr-CO2 and the operational area located in the passivity region composed of Cr2O3 and Cr(OH)(3)(s). (c) 2018 Elsevier Ltd. All rights reserved.