Corrosion behaviour of carbon steel in different concentrations of HCl solutions containing H2S at 90 °C

The corrosion behavior of SAE-1020 carbon steel in H2S-containing solutions with different concentration of HCl at 90 °C was investigated by weight loss, electrochemical measurements, SEM and XRD analysis. The results showed that the corrosion rate of carbon steel increased with increasing HCl concentration. Uniform corrosion was found on the carbon steel surface in H2S + HCl solutions, while corrosion cavities were observed in the solution only containing H2S. The ratio of Faradaic process of total corrosion process increased with the increase of HCl concentration. The corrosion products were solely composed of mackinawite in the H2S-containing solutions with or without HCl.

Research highlights
► The corrosion rate of carbon steel increased with increasing HCl concentration.
► Uniform corrosion was found on the carbon steel surface in H2S + HCl solutions, while corrosion cavities were observed in the solution only containing H2S.
► The ratio of Faradaic process of total corrosion process increased with the increase of HCl concentration.
► The impedance diagram were tried to analyze from the theoretical calculation.