A local electrochemical probe was combined with the thin foil penetration technique to study the corrosion propagation of a reduced number of grain boundary traces (in-plane) propagating inside a 60 mu m thick foil of AA2024. This local and "in-volume" approach allowed analysis of the current transient resulting from the full penetration of the selected intergranular paths. By coupling a 2D spatially resolved electrochemistry to digital optical observation on the back side of the foil, it was possible to relate the current transient to the successive steps of the "in-volume" propagation of intergranular corrosion. (C) The Author(s) 2019. Published by ECS.