Abstract
A Pt microelectrode was used to measure the oxygen consumption by redox reduction (ORR) on electrochemically polarised zinc in the redox competition mode. Zinc was polarised in the active and passive state, using a pH 7 and pH 13 solution, respectively. At pH 7, the oxygen concentration measured at a distance of 50 μm from the zinc surface, using the Pt microelectrode, is 15–60 % of the bulk oxygen concentration. Therefore, correspondingly, the oxygen consumption by zinc (due to ORR) is 40–85 % of the bulk oxygen concentration. At pH 13, where zinc undergoes passivation, the oxygen consumption by zinc is 70–80 % of the bulk oxygen concentration. The ORR rate on the surface of zinc passive films (ZnO/Zn(OH)2) is thus significant when compared to that on bare/actively corroding zinc. The influence of the electrode kinetics of zinc corrosion, on oxygen diffusion towards the metal surface has been investigated in this study.
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