Electrochemical Corrosion Behavior of 80S Steel in the Produced Fluid of Low-Sulfur Gas Well

In this paper, the electrochemical corrosion behavior of 80S steel in the produced fluid of low sulfur gas well was studied. The effects of temperature and sulfur content on the corrosion of 80S steel were studied by potentiodynamic polarization and electrochemical impedance spectroscopy. The results show that with the increase of temperature, the corrosion potential (Ecorr) of 80S steel decreased, and the corrosion current density increased first and then decreased. With the increase of sulfur content in the medium, the corrosion potential of 80S steel showed a negative trend, and the corrosion current density increased. The Nyquist diagram of 80 S steel at 40 ℃ shows the characteristics of capacitive reactance arc in medium-high frequency region and inductive reactance arc in low frequency region. At 65 ℃ and 90 ℃, the capacitive reactance arc in medium-high frequency region and capacitive reactance arc in low frequency region are presented, and the inductive reactance arc disappears. With the increase of temperature, the charge transfer resistance (Rt) shows a trend of decreasing first and then increasing slightly, that is, the corrosiveness of the medium increases first and then decreases. With the increase of sulfur content in the medium, the capacitance arc of 80S steel shows a decreasing trend. After adding different sulfur contents, the maximum phase angle of Bode spectrum in the basic medium moves to the direction of increasing frequency. After adding different amounts of Na2S·9H2O, the charge transfer resistance (Rt) of 80S steel is greatly reduced compared with the Rt value in the basic medium, that is, the corrosion of the medium to 80S steel is greatly increased.