Analysis of interfacial reactions by the use of chemical potential diagrams

The interfacial reactions of FeO/Cr, Cu2O/Ni, Cu2O/Fe, and Ti/Al2O3 at elevated temperature and the corrosion behavior of low Cr steels in an aqueous system in a CO2 environment were analyzed by applying the chemical potential diagrams for the Fe-Cr-O, Cu-Ni-O, Cu-Fe-O, Ti-Al-O, Fe-C-O-H-e-, and Fe-Cr-C-O-H-e- systems. These diagrams were constructed using the Gibbs energy changes for formation of the compounds involved. The reaction paths and the diffusion behavior of these interfacial reactions were reasonably explained by a simple model based on a steady state approximation and local equilibrium at the interface, which predicts that the reaction path should be represented by simple lines in the chemical potential diagrams.