Effect of Elemental Sulfur on Corrosion in Sour Gas Systems

The corrosive interaction of wet elemental sulfur with construction materials is reviewed, emphasizing effects of alloy composition (carbon steels, ferritic steels, austenitic steels, ferritic-austenitic [duplex] steels, Ni- and Co-base alloys, and titanium and its alloys), medium composition (salts, partial pressures of H₂S and CO₂, and acetic acid), and environmental conditions (temperature 20 to 250°C, stress). A summary of relevant physical and chemical properties of elemental sulfur is given to provide the fundamental basis for the understanding of sulfur corrosion. The different corrosion mechanisms found in the literature are critically discussed. Considering all data available, a mechanism is proposed explaining the electrochemical role of sulfur in the (physically) dissolved, solid, and liquid states. Methods for corrosion protection are outlined for carbon steels and corrosion-resistant alloys (CRA).