Diffuse Interface Modeling and Multi-Scale Relay Simulation of Thermal Oxidation of Metals

The oxidation kinetics of metals/alloys at elevated temperature is essential to the corrosion-life prediction of the structural materials in advanced energy systems. The oxide film growth on metal surface typically involves coupling of chemical reaction, ion diffusion and electrostatic interaction. A diffuse interface oxidation model plus a multi-scale-relay algorithm are developed to address the essential processes and their interplay over a wide range of length/time scale during metal oxidation. As a result, the transition of growth law of oxide films across orders of magnitude in length/time is computationally captured without a priori assumptions. The results are compared to the oxidation models developed by Wagner, Kröger, Deal and Grove, and Fromhold et al. The common assumptions used in the literature such as steady state, local equilibrium and local charge neutrality and their validity are investigated.