Corrosion of Spheroidal Graphite Cast Iron GGG40 in Anoxic Opalinus‐Clay Water: Influence of Hydrostatic Pressure

The corrosion of spheroidal graphite cast iron GGG40 in artificial geological water under anaerobic conditions at 30°C was studied under hydrostatic pressures of 0.5 and 10.0 MPa by electrochemical polarization and impedance spectroscopy. The chemistry and the morphology of the corroded surface were investigated by SEM‐EDX and local XPS. High hydrostatic pressures increase the corrosion rate by a simultaneous acceleration of the anodic and cathodic reactions caused by adsorbed atomic hydrogen generated by the water reduction. This activates the anodic dissolution of ferrite and reduces the coverage of poor passivating iron oxides. The release of silicon in the cast iron matrix induces the formation of iron phyllosilicates adhered to the surface.