Corrosion Behavior of 110S Tube Steel in Environments of High H2S and CO2 Content

The corrosion behavior of the 110S tube steel in the environments of high H2S and CO2 content was investigated by using a high-temperature and high-pressure autoclave, and the corrosion products were characterized by scanning electron microscopy and X-ray diffraction technique. The results showed that all of the corrosion products under the test conditions mainly consisted of different types of iron sulfides such as pyrrhotite of Fe0.95S, mackinawite of FeS0.9, Fe0.985S and FeS, and the absence of iron carbonate in the corrosion scales indicated that the corrosion process was controlled by H2S corrosion. The corrosion rate of the 110S steel decreased firstly and then increased with the rising of temperature. The minimum corrosion rate occurred at 110°C. When the H2S partial pressure PH2s below 9 MPa, the corrosion rate declined with the increase of Ph2s. While over 9 MPa, a higher PPh2s resulted in a faster corrosion process. With the increasing of the CO2 partial pressure, the corrosion rate had an increasing trend. The morphologies of the corrosion scales had a good accordance with the corrosion rates.