Interaction between carbon steel and low-pH bentonitic cement grout in anoxic, high temperature (80 °C) and spatially heterogeneous conditions

Anoxic corrosion processes impacting carbon steel samples for both intimate and imperfect metal/ low-pH bentonitic cement grout (BCG) contacts were studied at 80 °C. SEM, XRD and µ-Raman spectroscopy analyses supported by geochemical modelling allowed a full characterization of the corrosion mechanism. Steel in direct contact with BCG suffered from localized corrosion (pits measuring up to 160 µm in depth after 150 days of exposure) principally triggered by the presence of HS-. Depending on silicate and sulphide ingress from the BCG towards the interface, neoformed magnetite may be converted to iron silicates and/or iron sulphides. •XRD, µ-Raman, SEM-EDX analysis combined with geochemical modelling.•Sulphides from bentonitic cement-grout induced localized corrosion.•Presence of pits measuring up to 160 µm (150 days of interaction).•Transformation of magnetite into Fe-silicates and Fe sulphides.