Local flux of hydrogen from magnesium alloy corrosion investigated by scanning electrochemical microscopy

• Detection of local flux of H2 for the analysis of the corrosion behavior of microstructural features.
• SECM maps and approach curves measurement showed time-dependent change of the corrosion process.
• Numerical simulations revealed a continual change in the size of active site and the local flux of H2 formation.

Herein, we report the successful electrochemical detection and quantification of H2 fluxes produced from a corroding magnesium alloy using the substrate-generation/tip-collection mode of scanning electrochemical microscopy (SECM). Using a platinum microelectrode, the variation in H2 fluxes was imaged revealing the time-dependent corrosion reaction. Our results demonstrate that through careful control of the corroding media and immersion time, quantitative SECM approach curves, devoid of convective effects, were acquired. Comparison to an idealized numerical model enabled the quantification of the local H2 flux for a given corroding area. These data demonstrated that the active site size increases throughout the reaction, whereas the flux of H2 generated at an active site increased for the first hour of immersion followed by decrease in the flux of H2 for times greater than 1 h.

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