The Influence of the Semiconducting Properties of Passive Films on Localized Corrosion Rates

摘要

A passive film with a high electrical resistance can lead to a small cathodic current and repassivation of metastable pits and crevices. Many passive films behave as semiconductors and cathodic current magnitudes can be related to the semiconducting properties of the films. In this study, Alloy C22 was investigated with Mott-Schottky (MS) tests in neutral and acidic solutions. The passive film forming on Alloy C22 was found to be n-type with measured charge carrier densities and flatband potentials that were frequency dependent. An expression developed by Brug et al.(1) was found to calculate flatband potentials consistent with polarization scans. Using this expression the charge carrier density was calculated to be 10{sup}21cm{sup}(-3) and the flatband potential was found to be pH dependent, but close to the hydrogen redox couple. Alloy's C22's low flatband potential may increase its resistance to stable localized corrosion in ambient environments.