Hydrogen Permeation as a Tool for Quantitative Characterization of Oxygen Reduction Kinetics at Buried Metal-Coating Interfaces

The electrochemical stability of the buried metal-organic coating interface of painted metal is crucially governed by how effectively the oxygen reduction reaction at the interface is inhibited. As this interface is not directly accessible for study by conventional electrochemical techniques, a new non-destructive method has been developed wherein hydrogen permeation is used to quantitatively measure the oxygen reduction kinetics underneath the coatings. Presented here are results obtained with an adaptation of the Devanathan-Stachurski cell where the oxygen reduction reaction kinetics on the coated exit is probed by monitoring the dynamic electrochemical equilibrium potential established as a result of oxygen reduction and hydrogen oxidation reactions. From the hydrogen uptake on the entry side thus a full current-potential relationship curve (I (U)) can be constructed. First tested on non-coated Palladium, the results show very good concurrence of the oxygen reduction currents from the permeation experiments and that from standard cyclic-voltammetry (CV) measurements in buffered and non-buffered acidic electrolyte and under alkaline condition. Initial results obtained on coated samples are also presented.