Metallic, oxygen-containing reaction products after polarisation of iron in H2S saturated saline solutions

Abstract Corrosion of Fe in H 2 S containing solutions is a general problem in oil production. Here, layers rich in the the tetragonal FeS modification mackinawite were grown by polarisation of iron 200 mV above the corrosion potential in H 2 S saturated acetic saline solution. These layers have no band gap above room temperature thermal energy, hence behave metallic. The sulfide layers are duplex layers, with an inner, oxide-rich and an outer, oxide-poor region. Strain induced by differences in oxygen content may be responsible for the poor adhesion between the two layers, which leads to eventual loss of the outer layer.