The methods of investigation of oxygen influence on corrosion and hydrogenation of pipe steel in hydrogen sulfide environments

An experimental installation was developed for corrosion tests of steels in mineralized environ­ments at different ratios of partial pressures of hydrogen sulfide and air. Corrosion and hydrogenation of 17G1S-U steel were studied in a chloride-acetate solution bubbled with hydrogen sulfide, air, and their mixtures. The addition of oxygen to a hydrogen sulfide en­vironment slows corrosion in short-term electrochemical tests. The con­centration of hydrogen sulfide in the solution decreases as a result of interaction with oxygen and cathodic reactions slow down. The corrosion rate of steel is accelerated in 1.5–2 times during long-term tests in a solution with a ratio of PH2S : Pair 1 : 10. Oxygen complicates the formation of a sulfide-containing layer on the steel surface due to the oxidation of sul­fides with the formation of hydrophobic inclusions of sulfur and iron hydroxide. Sulfide films lose their barrier properties: their porosity increases, thickness and adhesion to the metal decreases. Selective etching of ferrite from the steel surface as a result of corrosion was recorded, thus leading to an increase in the real contact area of the metal with the environment and corrosion acceleration with time