In a recent work [5], we combined local electrochemical probe and thin foil penetration techniques to select only one grain boundary propagating on the longitudinal direction (rolling induces long grains, up to 700µm length, leading to a columnar microstructure). In this presentation, the combination of the specially designed microelectrochemical cell controlled by a SECM stage with a direct optical interrogation of the backside of a 50µm thick foil AA2024 will be described. This local and “in volume” approach allowed us to analyze the current transient resulting from the full penetration of a well-selected intergranular path. By linking the 2D spatially resolved electrochemistry to optical observation on the backside of the foil (1D), it was possible to relate the total current to the successive steps involved during the “in volume” attack (3D) of a well-defined grain boundary trace.
It will be discussed how this approach could be applied to deduce the IGC propagation rate from mass balance using the Faraday law and could support more robust assumptions on the effect of microstructure on IGC propagation rate because it would be easier to manage a spatial control of the location of the IG attack.
Acknowledgements
This work is supported by French ANR-14-CE07-0027-01 – M-SCOT: Multi Scale COrrosion Testing.
References
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