Iron and steel corrosion mechanisms in a carbonate rich pore water: Multiscale characterization of the corrosion product layers

Corrosion experiments were performed on a ferrito‐pearlitic (P285‐NH) and a ferritic steel (Armco) in a synthetic solution representing the Callovo‐Oxfordian porewater during a month at 120°C. Corrosion product layers (CPLs) were characterized from micro to nanoscale in terms of morphology (electron microscopies), composition (energy dispersive X‐ray spectroscopy), and structure (µ‐Raman, selected area electron diffraction). Both systems present a Ca‐siderite bilayer which interface locates the metal original surface, and nano to micrometric magnetite islets on the internal carbonated layer and at the M/CPL interface. The impact of cementite is highlighted in terms of morphology of the CPL and corrosion mechanism.