Revealing the Role of Oxygen Reduction Rate and Degradation Time on the Buried Metal/Coating Interphase Delamination Behavior

Oxygen reduction reaction (ORR) is fundamentally importance to the cathodic delamination process as it is responsible for the degradation of the organic coating/metal interphase. It is of significant interest to measure the rate of ORR as it directly determines the electrochemical stability of the interphase. Hydrogen permeation-based potentiometry (HPP) is a recent approach developed to quantify the ORR kinetics at such a buried metal/organic coating interphase. In this work, the HPP technique has been used to study the role of radical intermediates of the ORR in causing degradation of this organic coating/metal interphase. To this end, by measuring the current-potential or I(U) curves derived by the HPP method for polarization at different magnitudes of ORR rate, as well as different durations of such polarization, the evolution of the interphasial degradation process has been monitored. An anodic shift in the I(U) curve was observed for low ORR rates that exists during the initial stages of delamination of the interphase, while at high ORR rates, an anodic shift between the I(U) curves with successive runs was measured.