Potential decay behavior of Fe-20Cr alloy was examined by potential decay test, X-ray photoelectron spectroscopy, and Mott-Schottky analysis. The potential decay behaviors characterized by a short plateau followed by 1st decay and a long plateau followed by 2nd decay to an active state were closely associated with the duplex layer structure of passive film. We demonstrate that the short plateau followed by 1st decay is due to rapid dissolution of outer non protective Fe(III) enriched (Fe, Cr) oxide/Cr(III) hydroxide layer, whereas the long plateau followed by 2nd decay is attributed to slow dissolution of inner protective Cr(III) enriched (Fe, Cr) oxide layer. (C) 2018 Elsevier Ltd. All rights reserved.