Corrosion Behavior of P110 Steel in Vapor-Liquid Phase of H₂S/CO₂ Coexistence System

Abstract

For studying the corrosion behavior and mechanism of tubing in high temperature and pressure vapor-liquid phase of H2S/CO2 coexistence system, the dynamic corrosion simulation experiment of P110 steel for oil casing in CO2/H2S coexisting system was carried out using the high temperature autoclave. The uniform corrosion rates and pitting corrosion rates of samples were calculated by the weight loss method, and the corrosion behavior characteristics of P110 steel in liquid phase and gas phase of CO2/H2S coexistence system were analyzed and studied by XRD, SEM/EDS and 3D optical profile microscope. Results showed that the uniform corrosion rate and pitting corrosion rate of P110 steel in the liquid phase environment were 0.026 3 and 0.208 1 mm/a, respectively, which were higher than the uniform corrosion rate(0.014 8 mm/a) and pitting corrosion rate(0.156 9 mm/a) of P110 steel in the gas phase environment. Moreover, the corrosion products formed on the surface of P110 steel in the liquid phase environment were mainly red-brown powdery loose FeCO3, and the corrosion products formed on the surface of P110 steel in the gas phase were mainly FeCO3 and black-brown dense and uniform FeS. FeS inhibited the further corrosion of the base material from corrosive medium of CO2, H2S and Cl. Besides, the corrosion of P110 steel in liquid and gas phases was mainly uniform corrosion, with localized pitting and a tendency towards localized corrosion.

Keywords

• h₂s/co₂; gas phase; liquid phase; p110; corrosion