  We introduce an experimental setup to chemically image corrosion processes at
metal-electrolyte interfaces under stagnant, confined conditions relevant in a
wide range of situations. The setup is based on a glass capillary, in which
precipitation of corrosion products in the interfacial aqueous phase can be
monitored over time with optical microscopy, and chemically and structurally
characterized with microscopic synchrotron-based techniques (X-ray
fluorescence, X-ray diffraction, and X-ray absorption spectroscopy). Moreover,
quantification of precipitates through X-ray transmission measurements provides
in-situ corrosion rates. We illustrate this setup for iron corrosion in a pH 8
electrolyte, revealing the critical role of O2 and iron diffusion in governing
the precipitation of ferrihydrite and its transformation to goethite. Corrosion
and coupled reactive transport processes can thus be monitored and
fundamentally investigated at the metal-electrolyte interface, with
micrometer-scale resolution. This capillary setup has potential applications
for in-situ corrosion studies of various metals and environments.
