Effect of H_2S on the Corrosion Behavior of Pipeline Steels in Supercritical and Liquid CO_2 Environments

摘要

The objective of the present study is to evaluate the corrosion properties of pipeline steels in CO_2/H_2S/H_2O mixtures with different amounts of water (under-saturated and saturated) related to a natural gas transportation pipeline. Corrosion behavior of carbon steel, 1Cr steel and 3Cr steel was evaluated by using an autoclave with different combinations of CO_2 partial pressure and temperature (8 MPa/25°C and 12 MPa/80°C) with 200 ppm H_2S. The corrosion rate of samples was determined by weight loss measurements. The surface morphology and the composition of the corrosion product layers were analyzed using surface analytical techniques (SEM and EDS). Results showed that the corrosion rate of materials in supercritical and liquid phase CO_2 saturated with water was very low (＜ 0.01 mm/y). However, adding 200 ppm of H_2S to the supercritical and liquid CO_2 system caused mild corrosion (＜ 0.5 mm/y). Reducing water content to 100 ppm in the supercritical and liquid CO_2 systems with 200 ppm of H_2S reduced the corrosion rate to less than 0.01 mm/y.