Influence of Hydrogen Sulfide on the Carbon-Dioxide Corrosion and the Mechanical Characteristics of High-Strength Pipe Steel

We study the corrosion resistance of steel from the strength group V-150 in model stratal waters saturated with carbon dioxide and a mixture of carbon dioxide and hydrogen sulfide in the following proportion: 50:50 (under pressures of P = 0.1 and 6 МPа at temperatures of 25 and 60°С). It is established that hydrogen sulfide decreases the corrosion rate almost threefold at room temperature and by an order of magnitude under the elevated pressure at elevated temperature, which is explained by the formation of a sulfide film based on mackinawite and triolite, which inhibits the carbon dioxide corrosion of steel. The corrosion currents of steel in the media saturated with carbon dioxide and with the gas mixture determined by the electrochemical method are almost identical and equal to ∼ 0.013 mА/cm2 . It is shown that the media saturated with gases do not affect the ultimate and yield strengths of steel. However, the proportionality limit increases by 6 and 17%, the relative narrowing becomes ∼ 4.8 and 5.2 times smaller, and the relative elongation becomes ∼ 4.8 and 9.1 times smaller for the model stratal waters with CO2 and with 50% CO2 + 50% H2S, respectively.