Penetration depth and transient oxidation of graphite by oxygen and water vapor

Equations are derived for the approach to equilibrium in the oxidation of graphite under assumptions of constant graphite density and linearized oxidation kinetics. A two-factor expression is assumed for the effective diffusivity. Equilibration may be estimated by observing the convergence of profiles with time or by means of an algebraic approximation. At large times, the profiles converge to the steady state. Oxidation depths show fair agreement with published measurements and follow closely the observed temperature trend.