Front dynamics during diffusion-limited corrosion of ramified electrodeposits
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Experiments on the diffusion-limited corrosion of porous copper clusters in thin gap cells containing cupric chloride are reported. By carefully comparing corrosion front velocities and concentration profiles obtained by phase-shift interferometry with theoretical predictions, it is demonstrated that this process is well-described by a one-dimensional mean-field model for the generic reaction A + B (static) -> C (inert) with only diffusing reactant (cupric chloride) and one static reactant (copper) reacting to produce an inert product (cuprous chloride). The interpretation of the experiments is aided by a mathematical analysis of the model equations which allows the reaction-order and the transference number of the diffusing species to be inferred. Physical arguments are given to explain the surprising relevance of the one-dimensional mean-field model in spite of the complex (fractal) structure of the copper clusters.
26 pages, 10 figures, submitted to J. Phys. Chem. B, high quality eps figures available at http://www-math.mit.edu/~bazant/papers
26 pages, 10 figures, submitted to J. Phys. Chem. B, high quality eps figures available at http://www-math.mit.edu/~bazant/papers