Respirometric in Situ Methods for Real-Time Monitoring of Corrosion Rates: Part III. Deconvolution of Electrochemical Polarization Curves

Abstract

A highly sensitive respirometric method is presented that allows real-time monitoring of reaction rates involving H2 and O2 during electrochemical polarization. The measurement approach is based on simultaneous monitoring of the changes in the total pressure and the O2 partial pressure inside a closed chamber. Hence, it is possible to quantify the rates resulting from reactions such as H2 evolution reaction (HER), O2 reduction reaction, and O2 evolution reaction as a function of the applied potential. As a result, deconvolution of the net electric current into cathodic and anodic partial reaction rates during electrochemical polarization can be obtained. It was demonstrated that the respirometric monitoring approach can reveal superfluous cathodic reactions from Al during cathodic polarization as well as during anodic polarization of Al and Mg AZ31. Thus, the true metal oxidation rate could be determined from the electric current and the cathodic reaction rates. Furthermore, the rate of the HER during cathodic electrodeposition of Zn was measured. Through respirometric monitoring of Ni and stainless steel at high anodic potentials, the rate of O2 evolution could be distinguished from electrode oxidation processes.

Corrosion Resistance of Biodegradable Zinc Surfaces Enhanced by UV-Grafted Polydimethylsiloxane Coating

“…The corrosion kinetics of the bare and coated Zn samples were further investigated by respirometric measurements in modified HS. A detailed description of the method and its application in corrosion measurements can be found in our previous publications, − and Section S6 in Supporting Information. Briefly, monitoring the cathodic reactions in aqueous media, specifically the hydrogen evolution reaction (HER) and the oxygen reduction reaction (ORR), allows for the inference of the amount of anodic reaction.…”