Effects of electrodeposited Zn nuclei on tunnel etching behavior of aluminum foil

Zn nuclei were electrodeposited on the surface of aluminum foil to induce tunnel etching. It is proved that the tunnels etched in this way are distributed more uniformly, and both of the merging of tunnels and the reducing of the foil thickness are weakened. These effects can be attributed to the mechanism that the Zn nuclei can serve as the favorable sites for tunnel initiation on aluminum foil surface owing to the formation of Al–Zn micro-batteries, whereas the rest area of aluminum foil is passivated. This mechanism is supported by the initial potential transient and impedance spectra.