Corrosion of steel in weakly acidic media at low H2S concentrations

Abstract

The influence of low concentrations of H 2 S (25-200 mg/L) on the corrosion rate of St3 steel in model stratum water was studied by gravimetric, electrochemical methods and the linear polarization resistance method from ten-day experiments. In a simulated solution with pH = 6, an increase in the concentration of H 2 S in the range 25-100 mg/L causes an increase in the protective effect of H 2 S. At 200 mg/L H 2 S, the corrosion rate rises, but remains lower than in the solution without H 2 S. Introduction of an organic inhibitor to solutions containing H 2 S in these concentrations enhances the protective effect. Electron microscopy was used to characterize the state of the metal surface after corrosion. In a simulated solution with a lower pH (3.6), only 25 mg/L of H 2 S causes a decrease in the corrosion rate of the steel.