A process and apparatus are presented for cleaning the tunnels of an electrochemically etched anode foil. The apparatus includes a tank, a fluid inlet and a fluid outlet, and one or more tranducers. The tank is designed to receive a plurality of cartridges, each of the plurality of cartridges having a reservoir and being designed to hold a metal foil. The fluid inlet and fluid outlet are coupled with at least one of the plurality of cartridges, and are designed to introduce and expel, respectively, a liquid from the reservoir within at least one of the plurality of cartridges. The one or more transducers are coupled to at least one wall of each reservoir, the one or more transducers being designed to sonicate the liquid within each reservoir at a frequency less than 300 Hz.