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

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Product Number: 51300-09565-SG

ISBN: 09565 2009 CP

Author: Lei Zhang, Minxu Lu and Jianwei Yang

Publication Date: 2009

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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 and CO2 partial pressure at the temperature of 60oC with a constant H2S/CO2 partial pressure ratio of 1.7. The rate of X60 was slightly 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 component 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.

Key words: wet gas, H2S/CO2 corrosion, H2S partial pressure, pipeline steel, general corrosion, pitting corrosion, hydrogen blistering