In situ electrochemical tunneling spectroscopy (TS) was used to investigate the electronic properties of n-type semiconductive passive films formed on metals. The tunneling current I-T for Pt, Fe and Ti was measured as a function of distance Z, bias voltage phi(B), and polarization potential phi(P) respectively. A comparison of I-T-phi(B) spectra of Pt and passivated metals showed that the tunneling barrier of the latter is dominated by the space charge layer in the passive film under anodic polarization. There were difficulties in measuring TS in the electrochemical system, such as the limitation of a narrow bias scanning range and the polarization effect of the tip electrode (TE) near the surface of the specimen, On the other hand, a wide range of potential scanning was achieved in I-T-phi(P) measurement because the polarization potential of the TE was kept constant during the phi(P) scan. In I-T-phi(P) spectra of the Ti electrode, formation and annihilation of the depletion layer and dielectric breakdown were clearly observed as a function of the electrode potential.