In previous studies, there has been no consensus on the semiconducting properties of passive films on pure chromium by either photo-electrochemical analysis or Mott-Schottky (MS) analysis. In this work, a knee-point (KP), which is an exotic phenomenon in MS plots for some passive films, was found to be independent of the oxidation of Cr3+ to Cr6+. This shiftable KP was observed for the first time, and a strong correlation between the KP and the corresponding direct-current variation of the film during the MS test was also found. The investigation of the capacitance-time relationship on the aging of passive films provided a rational interpretation of the KP for the film investigated. These findings demonstrated that the film formed on Cr was not an ideal semiconductor, and MS analysis was not applicable to the film. (C) The Author(s) 2017. Published by ECS.