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 degrees 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 (mu-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.