Corrosion Resistance of 20^# and L245NS Pipeline Steels in Low-Sulfur Oilfield Environment

The corrosion behavior of 20^# and L245NS pipeline steels in simulated sulfur-free and low-sulfur oilfield environment with coexistence of H₂S/CO₂ was analyzed by potentiodynamic polarization curves and electrochemical impedance spectroscopy. Scanning electron microscope and energy dispersive spectrometer were used to analyze the micro morphology and composition of corrosion products on the surface. The results showed that the corrosion potential (E_corr) of 20^# and L245NS pipeline steels in low-sulfur oilfield environment had a small change, and the corrosion current density (J_corr) was significantly reduced. Under the same conditions, the J_corr of the L245NS pipeline steel was slightly smaller than that of 20^# pipeline steel. The electrochemical impedance spectra of 20^# and L245NS pipeline steels in sulfur-free oil field environment showed the time constant characteristics of capacitive reactance arc in the medium and high frequency region and inductive reactance arc in the low frequency region. The inductive reactance characteristics in low frequency region in low-sulfur oilfield environment disappeared. The corrosion resistance of L245NS pipeline steel in low-sulfur oilfield environment was slightly better than that of 20^# pipeline steel.