Oxidation of chukanovite (Fe 2 (OH) 2 CO 3 ): Influence of the concentration ratios of reactants

International audienc

Role of previously formed corrosion product layers on sulfide-assisted corrosion of iron archaeological artefacts in soil

International audienceIron archaeological nails (16th century) were used as representative of the mild steel structures envisaged for the storage of nuclear waste. The influence of sulfide species on the corrosion behavior of the nails was investigated via the thorough description of the modifications undergone by the corrosion products surrounding the metal after re-immersion in deaerated sulfide solution. The only observed modification was the formation of FeS at the corrosion product layer/soil interface. The corrosion product layer, mainly composed of FeCO3, acts as protective barrier, the reactivity of FeCO3 preventing sulfide species to reach the metal and influence the corrosion process

Influence of soil moisture on the corrosion processes of carbon steel in artificial soil: Active area and differential aeration cells

International audienc

Electrochemical Monitoring of Steel/Soil Interfaces during Wet/Dry Cycles

International audienc

On the formation and transformation of Fe(III)-containing chukanovite, FeII2-xFeIIIx(OH)2-xOxCO3

International audienc

End-Cretaceous akaganéite as a mineral marker of Deccan volcanism in the sedimentary record

An enigmatic chloride-rich iron (oxyhydr)oxide has been recently identified together with mercury anomalies in End-Cretaceous marine sediments coeval with the Deccan Traps eruptions. The mineral was observed in Bidart (France) and Gubbio (Italy), suggesting a widespread phenomenon. However, the exact nature and origin of this Cl-bearing mineral remained speculative. Here, we characterized the accurate composition and nanostructure of this chloride-rich phase by using micro-Raman spectroscopy, Transmission (TEM) and Scanning (SEM) Electron Microscopy on Focused Ion Beam foils. We also provide new evidence of its occurrence in Zumaia, a reference KPg section from Spain. Results confirm akaganéite (β-FeOOH) as the main phase, with chloride content of 3-5 atomic weight %. Akaganéite particles are constituted by the aggregation of nanorods of akaganéite. Internal structures contain empty spaces, suggesting formation in a low-density (atmospheric) environment. This new mineralogical evidence supports the hypothesis that the observed akaganéite was formed in the Deccan volcanic plume and was transported to the Atlantic and Tethysian realms through the stratosphere. Therefore, akaganéite provides a potential new sedimentary marker to identify the imprint of the Deccan eruptions in the stratigraphic record and is evidence of volcanic halogen degassing and its potential role for the Cretaceous-Tertiary mass extinction