EIS Study of Temperature and H2S Concentration Effect on API 5LX65 Carbon Steel Corrosion in Chloride Solution

A study has been carried out on the effect of temperature and H2S concentration on the corrosion of API 5LX65 carbon steel in a flowing 3.5 wt% sodium chloride （NaCI） solution by using electrochemical impedance spectroscopy （EIS）. The Nyquist curves were used to characterize the corrosion behavior of API 5LX65 carbon steel in 3.5 wt% sodium chloride （NaCI） solution with H2S concentrations 50, 150, 300, 500 and 750 mg/L at variaton of temperatures 30, 50, 70℃, and at a fluid rotation speed of 50 rpm during 3 hours. The EIS analysis showed that the corrosion rate of carbon steel in 3.5% NaCl solution containing 500 mg/L tt2S, increases with temperature rise from 30 ℃ to 70 ℃. The while the carbon steel corrosion in 3.5% NaCl solution at 50℃ with H2S concentration varied from 50 to 500 mg/L, showed that the steel corrosion rate raises with increasing H2S concentration. Combined observations using SEM, EDS and XRD reveal the formation of corrosion product layer which consists mainly of iron sulfide （FeS）. The sur