An in-situ Raman study on the oxidation of mackinawite as a corrosion product layer formed on mild steel in marginally sour environments

Abstract

Abstract An in situ Raman flow loop with flow cell was developed to enable observation of the mackinawite corrosion product layer generated in marginally sour environments with traces of oxygen ingress. As a result, the mackinawite corrosion product layer was found to be oxidized into magnetite in the solution when [O2](aq) > 3 ppb(w), which was linked to the pitting initiation of mild steel (API X65) in marginally sour environments. The 2D precursor of nano-crystal mackinawite, the chemisorption FeS layer, Sads (Fe), was detected by ex situ Raman microscopy.