Chaos during the Growth of an Artificial Pit

The current vs. time behavior of a silver electrode in a one-dimensional artificial pit configuration was followed under potentiostatic control in 1M HCIO₄. The current decay followed power law behavior in time, i = t~^-y, with y = 0.5. Within specific regimes of applied potential and pit depth, the current was found to oscillate both periodically and chaotically with time. The oscillations result from an instability of a salt film on the metal surface. Owing to the instability of the salt film, a porous metal layer develops on the electrode surface, and this has a variety of implications in the field of corrosion.