Steel Corrosion in Hydrogen Sulfide Containing Oil Field Model Media

Corrosion resistance and electrochemical behavior of X60 steel in model solutions of the Samotlor and Usinsk fields and in the NACE medium recommended for accelerated corrosion testing of pipe steel for the oil industry is investigated. It is established that the steel corrosion resistance studied increases with an increase in hydrogen sulfide content. In model environments containing hydrogen sulfide, the surface of the specimens is covered with point corrosion damage in contrast to the model hydrogen sulfide-free environment of the Samotlor field in which corrosion is uniform in nature. With an increase in medium hydrogen sulfide content the free corrosion potential for steel X60 shifts into the region of positive values from – 0.44/n.h.e/ in the model medium of the Samotlor field to + 0.35 V/n.h.e/ in the NACE medium (saturated hydrogen sulfide solution) that is caused by formation of an iron sulfide film. Polarization curves for steel X60 in the solutions indicate an accelerating effect of hydrogen sulfide on cathodic and anodic processes and confirm known data for its stimulating effect on corrosion and the nature of corrosion damage. The reduction observed in cathodic process rate in hydrogen sulfide-containing media is caused by formation of an iron sulfide film that reduces the electrode active surface.