Effect of H2/CO2 partial pressure ratio on the tensile properties of X80 pipeline steel in the absence and presence of water

The effect of H2/CO2 partial pressure ratio on the tensile properties of X80 pipeline steel in the absence and presence of water were investigated by slow strain rate test (SSRT) and scanning electron microscope (SEM) measurements in this paper. The results show that the tensile strength and elongation to failure of X80 pipeline steel in H2/CO2 atmosphere were deteriorated significantly. The relative tensile strength and plasticity loss of X80 pipeline steel increased with increasing H2/CO2 partial pressure ratio in the absence of water. The increasing volume fraction of hydrogen gas is the key influencing factor in this condition. For the H2/CO2 environments in the presence of water, the relative tensile property loss decreased first and then increased with H2/CO2 partial pressure ratio. The probable reason is that the corrosion process changed gradually from CO2-dominant to H2-dominant. Water played a significant role in the tensile property damage of X80 pipeline steel in the H2/CO2 environments.