09565 Effects of Pressure on Wet H2S/CO2 Corrosion of Pipeline Steel

Wednesday, March 25, 2009: 10:45 AM
C303 (Georgia World Congress Center)
Lei Zhang , University of Science & Technology, Beijing, China
Jianwei Yang , University of Science and Technology Beijing, Beijing, China
Minxu Lu , School of Materials Science and Engineering, University of Science & Technology Beijing, Beijing, China
Wet H2S/CO2 environment in gas gathering pipelines of a sour gas filed was simulated in a high temperature and high pressure autoclave. Corrosion experiments were carried at a constant H2S/CO2 partial pressure ratio of 1.7 and H2S partial pressure at 0.15MPa, 0.33MPa, 1.5MPa and 2.0MPa respectively. Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) were used to analyze corrosion scales. Effects of high H2S partial pressure on corrosion of API-X52 and X60 pipeline steels were discussed. The results show that the corrosion rate of the two steels increased with the H2S partial pressure at the temperature of 60oC. The rate of X60 was appreciably higher than that of X52 steel. General corrosion was primary at the H2S partial pressure of 0.15MPa, 0.33MPa and 1.5MPa, but localized corrosion was observed at the H2S partial pressure of 2.0MPa. The corrosion process was controlled by H2S and mackinawite was the dominant composite in the corrosion products. The grain size of corrosion products decreased with H2S partial pressure increasing, coupled with the obviously change in crystal morphology and structure, which reduced the protection ability for steels. In addition, hydrogen blistering and hydrogen-induced crack were observed in the X60 steel.