Corrosion front roughening in two-dimensional pitting of aluminum thin layers

A smooth to fractal transition of the corrosion front has been observed during two-dimensional pitting of Al thin films. The propagation of the initially smooth front ceased spontaneously, leaving behind a self-similar coastline with fractal dimension D-f = 1.33 +/- 0.01. The roughening transition can be interpreted within the framework of the spreading bond percolation model with trapping. Quantitative agreement has been found between model calculations and the dynamic exponents characterizing the temporal behavior of the propagation velocity as well as the roughness of the front.