Corrosion Behavior of X52 Steel in Simulated Environment of a Highly Sour Gas Field

The corrosion characteristics of X52 pipeline steel in aqueous solution with 1.5 MPa H2S and 0.9 MPa CO2 at 60 ℃, and the effects of Cl- and element sulfur on the corrosion were investigated by high-temperature and high-pressure autoclaves, and the surface morphology and composition of corrosion product were studied by SEM and XRD methods. The results showed that the main corrosion products of X52 in the H2S/CO2 environment were mackinawite and troilite, the corrosion was controlled by H2S and dominated by uniform corrosion. The surface corrosion product film had a certain inhibitory effect on the general corrosion of X52 steel, but could not prevent hydrogen blisters. The corrosion rate of X52 first increased and then decreased with the increase of Cl- concentration, the protectiveness of the corrosion product was poor due to the obvious reduction of the product crystallization degree. The effect of elemental sulfur was similar to that of Cl- ions, and the corrosion rate was up to 14.70 mm/a when the content of elemental sulfur was 5 g/L. Elemental sulfur was prone to deposition when its content was too large, resulting in the decrease of corrosion rate.