Abstract
Two kinds of alminum specimens were prepared: 1) chemically polished specimen (CP-specimen) and 2) surface-roughened specimen (PD-specimen) obtained by removing a porous anodic oxide film through dissolution in an H3PO4/CrO3 solution. The change in the surface roughness of CP- and PD-specimens during anodizing in a neutral solution was monitored with in situ atomic force microscopy (AFM) and transmission electron microscopy (TEM) as a function of anode potential. The change in surface roughness was also simulated mathematically, by assuming the Pilling-Bedworth ratio is constant during film growth.
The CP- and PD-specimens had a network structure of ridges with respective heights of 30 and 70nm. The ridge height decreased sharply during the early stage of anodizing and gradually during the late stage. The PD-specimen showed a rough surface even at anode potential, where Ea=150V.
A theoretical simulation of the decrease in the ridge height with the anode potential corresponded well to the experimental results obtained by AFM and TEM.
