Growth of Tunnels during Aluminum DC Pulse Current Etching

High-purity aluminum foil was etched with DC pulse current in acids solutions at first time. Experiments indicated that tunnels morphology was influenced by current density, pulse duty-cycle and frequency of DC pulse current, tunnels began to grow when the current density reached to 0.8A cm-2, and tunnels grew along three directions to form a netlike construction in the surface of aluminum foil, which increased effectually surface areas of aluminum foil. In addition, when aluminum was etched in the solution of 1 N HCl +0.8 N HNO3,tunnels morphology shows that tunnel does not grow continually during DC pulse current etching, so it is a method to study the mechanism of tunnel growth, for example period of tunnel growth, velocity of tunnel growth. The experimental results are discussed according to tunnels morphology.