Abstract
The kinetics of growth of anodic oxide films in different electrolytic solutions, and in a range 1–32 mA cm−2 of current density has been investigated. By interferometric measurements an increase in the electrical field strength has been measured with increasing film thickness at all current densities and in all solutions. This finding has been attributed to the existence of a mobile ionic space charge. A test of this hypothesis has been made by fitting the 
vs. 
curves on the basis of Fromhold's theory. Nonlinear Tafel plots have been obtained in sulfuric acid and in carbonate solutions while a straight line behavior was observed in sulfamic acid solutions. Lower dielectric constant values also have been measured for films formed in the former two solutions which are known to give incorporation of anions in 
films. No incorporation of anions seems to occur when anodization process is performed in sulfamic acid solutions. Some discrepancies between experimental results and the existing theory have been pointed out.