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Mechanisms of localized corrosion of carbon steel associated with magnetite/mackinawite layers in a cement grout
Author(s) -
Robineau Mathieu,
Sabot René,
Jeannin Marc,
Deydier Valérie,
Crusset Didier,
Refait Philippe
Publication year - 2021
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.202011696
Subject(s) - mackinawite , corrosion , materials science , magnetite , metallurgy , carbon steel , dielectric spectroscopy , raman spectroscopy , anode , polarization (electrochemistry) , anaerobic corrosion , grout , galvanic corrosion , electrode , chemical engineering , electrochemistry , composite material , chemistry , engineering , physics , optics
Carbon steel electrodes covered with a specific low‐pH cement grout (pH ~10.7 at 20°C), designed for nuclear waste management applications, were immersed for 30 days in a 0.01‐M NaCl + 0.01‐M NaHCO 3 solution (pH 7 measured at 20°C), in aerated conditions, at 80°C. The corrosion processes were studied by voltammetry and linear polarization resistance measurements while the corrosion product layers were analyzed by µ‐Raman spectroscopy and X‐ray diffraction. Most of the electrodes (75%) suffered from localized corrosion, a phenomenon associated with the formation of a heterogeneous Fe 3 O 4 /FeS layer. It is proposed that the mechanisms of the particular corrosion process observed here are associated with galvanic effects, the large magnetite‐covered zone acting as cathode and the locally mackinawite‐covered zones being anodic regions.