Applied Mathematics Colloquium
University of Washington
March 9, 1999

Title:  "Diffusion-Limited Corrosion of (Very) Porous Solids"

Speaker: Martin Z. Bazant, Dept. of Mathematics, M.I.T.

Coauthors: H. A. Stone, Div. of Engineering and Applied Sciences, Harvard
	C. Leger and F. Argoul, Centre de Recherche Paul Pascal, Bordeaux

Abstract:


A combined theoretical and experimental study is presented which
explores whether the mean-field (continuum) model of Galfi and Racz
(1988), originally developed for two diffusing reactants, can also
describe the corrosion of a porous solid, i.e. the case of one
diffusing and one static reactant. First, a uniformly-valid asymptotic
approximation consisting of two matched similarity solutions (for the
"reaction front" and "diffusion layer") is derived for a 
mA + nB(static) -> C(inert)  system of planar symmetry.  The theoretical
predictions are then compared with experimental concentration profiles
(obtained by phase-shift interferometry) for the corrosion of ramified
copper electrodeposits in cupric chloride solution immediately
following electrodeposition. It is found that many aspects of the
experimental data are well-described by the mean-field model with
m=n=1.  The mathematical analysis also predicts the physical effects
of higher order corrosion reactions m, n > 1.