Ultrasonic effect on etching tunnel morphology and distribution of aluminum foil

Etching aluminum foil was prepared by electrochemical DC etching under ultrasonic superimposition. Specifically, the relationship of electrochemical behavior, interface behavior and mass transfer enhancement from ultrasound was investigated intensively by chronopotentiometry, potentiodynamic polarization, cyclic voltammetry and electrochemical impedance spectra. Meanwhile, the etching specimens were characterized by SEM, N2 adsorption and XRD patterns measurements. The results showed that ultrasonic agitation inhibited the growth of aluminum oxide film and facilitated pit initiation effectively via increasing the Cl− adsorption on electrolyte/aluminum oxide film interface, and strengthened the inward/outward migration of Cl− and AlCl3 within tunnels by thinning the thickness of diffusion layer and decreasing the electrolyte resistance. Moreover, the double layer capacitance Cdl, pit density, average pit size/tunnel length and its homogeneity are all enhanced under ultrasonic superimposition.