Corrosion scale composed of iron-sulfur compounds can significantly affect the corrosion process. However, the transition of different crystals along with time and the protection effect of different corrosion products are not well understood. In this paper, the H2S/CO2 corrosion of pipeline steel under 1.5 MPa H2S and 0.2 MPa CO2 partial pressures at 90 °C was studied. SEM and XRD were used to investigate the characteristics and evolution of corrosion product. Results indicated that the corrosion rate of pipeline steel decreased and then tended to steady with time. At the initial corrosion stage, the corrosion scale was made mainly of mackinawite crystals with a small amount of FeS crystals. After a certain period, pyrrhotite crystals appeared on the surface of the corrosion scale and then the corrosion process was controlled by the growth of pyrrhotite.

Subject
Scanning electron microscopy, X-ray diffraction, Thin films, Mackinawite, Corrosion rate, Iron sulfides, Pipelines, Pyrrhotite, Corrosion products, Corrosion scales, Crystal growth, Steel, Corrosion protection
Keywords:
high H2S, CO2 partial pressure, corrosion scale, mackinawite, pyrrhotite
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2012
Association for Materials Protection and Performance (AMPP)
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