Corrosion at the carbon steel-clay compact interface at 90 °C: Insight into short- and long-term corrosion aspects

Rods of low alloy carbon steel were corroded under anoxic conditions in compact clay at 90 degrees C. Gravimetrically-assessed corrosion damage equalled 8.5 mu m at 7 months, then slowly increased to 29.5 mu m at 76 months. The corrosion damage was heterogeneous at 7 months, and two distinct aspects coexisted: steel was replaced by (Fe,Si,O) corrosion products in some areas, and by Si-poor hydroxide and covered by akaganeite (FeO(OH,Cl)) in others, indicating corrosion in suboxic conditions. A magnetite fringe contacted the steel surface. For greater reaction times, akaganeite disappeared, and only (Fe,Si,O) corrosion products containing Fe sulfide and chukanovite were detected.