PNNL

Abstract

Models for the corrosion and pitting of passive metals such as aluminum usually involve the migration of point defects through the native oxide film as the rate limiting step. Hydration of the surface oxide could also influence the protective nature of the film. Secondary ion mass spectrometry (SIMS) has been used in conjunction with isotopic labeling to determine the extent and rate of passive film hydration on aluminum. The rates at which oxygen- and hydrogen-contianing species migrate through the film has been determined as a function of temperature and applied potential (cathodic and anodic polarization). The results suggest that defects such as hyroxide ions are prevalent and mobile in the oxide film, influencing the kinetics and mechanisms of corrosion processes.