Electric properties and pitting susceptibility of passive films formed on iron in chromate solution

Electric properties and pitting susceptibility of passive films formed on i ron in 0.01 M Na2CrO4 solution was investigated by using Mott-Schottky anal yses, electrochemical noise analyses and anodic polarization curve measurem ents. It was found that the passive films were very disordered n-type semic onductors with two level donors, shallow and deep. The donor concentrations decreased as the passive film was formed at more positive potentials. The passive films were susceptible to pitting in the solution containing 0.05 M chloride ions. The pitting susceptibility of the passive film was improved as the donor concentration in the passive film decreased. (C) 1999 Elsevie r Science S.A. All rights reserved.