Abstract
The capacity of the etched aluminum foil used in electrolytic condensers is determined by its surface area A study was conducted on the initiation and growth of pits in high-purity aluminum foils during DC etching in hot hydrochloric acid, and pit structures after etching were observed by SEM images of resin replicas
(1) The electrode potential during DC etching moved from a period of high potential to one of stability with a transition period of up to 50ms. Pits were initiated during the high-potential period, and pits with facets grew during the stability period
(2) The high-potential and stability periods were reproduced by potentiostatic electrolysis, and the structures of the pits were examined It was found that pits were initiated at an electrode potential of about -400mV vs S.C.E, and pits with facets grew at an electrode potential of about -670mV vs. S C E An attempt was also made to represent the direction of pit growth using fractal dimensions
