Synergistic Effect of O 2 and H 2 S on the Corrosion Behavior of N80 Steel in a Simulated High-Pressure Flue Gas Injection System

The aim of this work was to understand the synergistic effect of O 2 and H 2 S on the corrosion behavior of N80 steel in a simulated high-pressure flue gas injection system. Weight loss measurements show that the presence of O 2 and an increase in temperature significantly accelerated the general corrosion rate of the N80 steel. We calculated a gray relational grade between different impact factors and the general corrosion rate from the results of an orthogonal experimental corrosion rate. The grade ranking of impact factors was: O 2 concentration (0.817) > temperature (0.706) > total pressure (0.689) > H 2 S concentration (0.665) > CO 2 concentration (0.517). Surface characterization of corrosion scales was done using scanning electron microscopy, energy-dispersive spectroscopy, x-ray powder diffraction, and 3D optical microscope analysis. The results show that in the O 2 -H 2 S-CO 2 -H 2 O coexistence system the products were composed mainly of FeCO 3 , FeS, Fe 2 O 3 , Fe 3 O 4 , and elemental sulfur. The results of the corrosion rate test and the characterization show that the presence of O 2 greatly accelerated the corrosion process and changed the corrosion mechanism. Elemental sulfur, which was generated by the reaction between the H 2 S and the O 2 , participated in the corrosion process of the N80 steel. It could be considered that the synergistic effect of O 2 and H 2 S accelerated the corrosion of the N80 steel. In addition, the porous structures of the corrosion scales and the severe local pits show that the high content of O 2 inhibited the formation of FeCO 3 and aggravated the corrosion of N80 steel.