The aim of this work is to study the evolution in time of the anodic behavior of passive materials and particularly its effect on their corrosion potential in natural waters. The effects of different hydrodynamic and biological conditions, previous formation of passive film, and galvanic coupling, are considered. The ennoblement of the corrosion potential has been related to the aging of the passive film by means of analyses on the equilibrium between cathodic and anodic current in the experimental polarization curve. Based on the results of the study, we can conclude that the evolution of the corrosion potential is due to a weak inhibition of the anodic process rather than an enhancement of the cathodic process.