Respirometric Studies on Transpassive Dissolution

Recently, we introduced respirometric methods for real-time monitoring of corrosion, both for atmospheric corrosion [1] and immersion conditions [2]. The approach is based on monitoring the rate of the cathodic reactions with help of different types of sensors; this enables to track the O2 reduction reaction and the H2 evolution reaction simultaneously. The set-ups have been used to study different corrosion scenarios under free corrosion conditions. Even more recently, the respirometric setups were coupled with electrochemistry [3, 4], enabling the corrosion cases to be studied not only at open-circuit conditions but also for potential-controlled systems. With this, it is possible for instance to de-convolute the sum current measured by potentiodynamic polarization curves into different cathodic and anodic partial reaction rates. For passive metal and alloys, transpassive dissolution is being explored, by quantification of the amount of oxygen evolving during transpassive dissolution that typically occurs at potentials above the water stability region (i.e., the net anodic electrical current/charge is a sum of partial currents for oxygen evolution reaction, OER, and for metal oxidation/dissolution). Therefore, a true metal oxidation rate can be determined that is not directly assessable from the electrochemical measurement. Examples will be presented, to illustrate the potential of these techniques to reveal insights into corrosion mechanisms of active and passive metals and alloys. References M. Strebl, M. Bruns, S. Virtanen, Editors’ Choice—Respirometric in Situ Methods for Real-Time Monitoring of Corrosion Rates: Part I. Atmospheric Corrosion, J. Electrochem. Soc. 167 (2020) 21510 M.G. Strebl, M.P. Bruns, G. Schulze, S. Virtanen, Respirometric In Situ Methods for Real-Time Monitoring of Corrosion Rates: Part II. Immersion, J. Electrochem. Soc. 168 (2021) 11502 M.G. Strebl, M.P. Bruns, S. Virtanen, Coupling Respirometric HER and ORR Monitoring with Electrochemical Measurements, Electrochimica Acta 412 (2022) 140152 M.G. Strebl, M. Bruns, S. Virtanen, Respirometric In Situ Methods for Real-Time Monitoring of Corrosion Rates: Part III. Deconvolution of Electrochemical Polarization Curves, J. Electrochem. Soc. 170 (2023) 061503