Mechanical attrition assisted DC etching aluminum foils with enhanced capacitance

The aluminum foils for high voltage aluminum electrolytic capacitors were DC etched in HCl–H2SO4 hybrid acids and the effects of in-situ mechanical attrition on the etching were studied in this work. Compared with the conventional etching, the distribution of etch tunnels was, under in-situ mechanical attrition, more uniform with high density of etch pits and long tunnels, which expands the surface area of etched Al electrode and greatly increases its capacitance. This effect is probably due to the mechanical attrition effects which are beneficial for the breakdown of the protective film and reducing concentration polarization in the bulk etchant solutions, inducing higher pit and tunnel density and increasing the survival rate of tunnels.