Effect of CO2 and H2S on the Corrosion Resistance of FV520B Steel in Salinity Water

The corrosion behavior of FV520B stainless steel in different salinity water was studied by electrochemical measurements such as potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS). The results showed that the open circuit potential (OCP) shifts negatively and the thermodynamic stability of FV520B steel decreases when CO2 and H2S were introduced into the salinity water (SW). The polarization curves of FV520B steel show typical passive characteristics in the salinity solutions. When CO2 and H2S are introduced into the SW, the corrosion current density of FV520B steel increases, the polarization resistance decreases, and the corrosion resistance decreases, and the corrosion resistance is the poorest in H2S salinity water. XPS analysis shows that the passive film of FV520B steel are mainly consist of oxides and hydroxides of Fe, Cr, Mo, Ni and Cu. With the introducing of CO2 and H2S, the content of Fe2+ and Cr3+ in passive film decreases, the content of Fe3+ and Cr6+ increases, and the corrosion resistance of passive film decreases. The corrosion resistance of FV520B steel in SW is significantly reduced by corrosive gas CO2 and H2S, and the corrosion resistance in H2S shows the worst.