Corrosion Behavior of Novel Cr2MoNbTi Pipeline Steel in CO₂ Environment

CO₂ corrosion is frequently encountered in oil and gas industry. The search for new sources of oil and gas has pushed the operational activities to harsher environment and this requires new tubing and pipeline materials which can endure tough circumstances. Low alloy steel containing Chromium, which fills the gap between carbon steels and corrosion resistant alloys in terms of cost and corrosion resistance, has aroused significant interest from steel enterprises and scholars. At present, these studies mainly focus on 3%–5%Cr steel, and little study concerns the 2%Cr steel, which is more economic and weldable. In this paper, novel Cr2MoNbTi steel was developed and the microstructure and mechanical properties were studied. Corrosion behavior of the Cr2MoNbTi steel immersed in the CO₂-containing solutions, which corresponded to the environment of bottom-of-line corrosion (BLC), was studied using high temperature-high pressure autoclave. In addition, dynamic high temperature-high pressure condensation autoclave was employed to simulate the top-of-line corrosion (TLC) environment and the corrosion behavior of the Cr2MoNbTi steel under wet gas environment was investigated. The composition and morphology of the corrosion scale were characterized by energy dispersive spectroscopy and scanning electron microscopy analyses. The results show that the Cr2MoNbTi steel exhibited uniform corrosion and presented good resistance to CO₂ corrosion compared with X65 pipeline steel.