In situ nano- to microscopic imaging and growth mechanism of electrochemical dissolution (e.g., corrosion) of a confined metal surface

Significance A surface forces apparatus was used with an electrochemical attachment to directly visualize electrochemical reactions, dissolution, and pitting on surfaces when confined in nanoscale gaps (or “crevices”) in real time. The results provide unique insights into how two closely apposed surfaces degrade under confinement, which is different from degradation of surfaces exposed to bulk solution. Degradation proceeds via local nucleation of “pits” at the periphery or center of the “contact area” that rapidly grow outward (in radius) and, more slowly, in depth, until the pits converge and the whole area has become one large pit. The results on a metal–inorganic interface are similar to previous observations on inorganic interfaces, and support a general mechanism of “pitting corrosion” at confined interfaces.