Weak Oxygen Transport Limitation

This section derives a more general analytical solution to the system of Equations 4.53 through 4.55 (Kulikovsky, 2012a). This solution corresponds to the mixed case of arbitrary proton transport and weak oxygen transport limitations, and is of particular interest, since the CCL in PEFCs usually works in this regime. 

Interphase inhibition [52] occurs where the inhibitive layer has a three-dimensional structure situated between the corroding metal and the electrolyte. The interphase layers generally consist of weakly soluble compounds such as oxides, hydroxides, carbonates, inhibitors, etc. and are considered to be porous. Non-porous three-dimensional layers are characteristic of passivated metals. The inhibitive efficiency depends on the properties of the three-dimensional layer, especially on porosity and stability. Interphase inhibition is generally encountered in neutral media, either in the presence or absence of oxygen. In aerated solutions, the inhibitor efficiency may be correlated with the reduction in the oxygen transport limited current at the metal surface. 

When a corrosive environment contains only small concentrations of an oxidizing agent, the corrosion rate is often limited by its transport. This behavior is typically found for corrosion by oxygen in neutral media or corrosion by protons in weakly acidic environments. 

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