A Study of the Oxygen Growth Laws of Anodic Oxide Films on Aluminum and Tantalum Using Nuclear Microanalysis of O16 and O18

Abstract

The oxygen growth laws of anodic oxide films on aluminum and tantalum were studied using the nuclear microanalysis of the O¹⁶ and O¹⁸ isotopes. The influence of current density and surface preparation on the growth laws has been demonstrated. The correlation of the results of nuclear microanalysis of O¹⁶ and of coulometric measurements allowed the determination of the dissolution current density during anodic oxidation of aluminum. This dissolution current was shown to be purely electrochemical. The values of the intercepts with the potential axis of the linear growth laws show that the overpotentials at the interfaces are smaller than 0.1V for current densities from some . Measurements of isotopic exchange of oxygen using O¹⁸ as a tracer allowed direct estimation of the oxygen exchange current without applied field. The results show that oxygen transfer at the oxide‐ solution interface, enhanced by field‐induced oxygen vacancies, is responsible for the growth of the anodic film.