Strength Sucker Rod Steel in High SO42- Environment

9 In some sour reservoirs and tertiary oil recovery blocks, SO42in solution can cause the corrosion 10 and corrosion fatigue of the sucker rods. In this paper, the corrosion behaviors of super-strength 11 sucker rod FG20 (16Mn2SiCrMoVTiA) steel in the well fluid are investigated by electrochemical 12 measurements, and electron probe micro-analyzer (EPMA) analysis. The results show that FG20 steel 13 has a favorable corrosion resistance in neural solutions. When the hydrogen ion content increases, 14 the hydrolysis of SO42greatly accelerates the corrosion of FG20 steel. The energy dispersive X15 ray(EDX)results demonstrate that the corrosion process of FG20 steel in neural well liquid is an 16 oxygen concentration process, and the protective FeCO3 and Fe2O3 on the surface of the samples can 17 prevent further corrosion. With the increase of the acidity in the well liquid, the corrosion process 18 converts into a sulphide concentration process, and the sloppy FeS and mackinawite film cannot 19 provide effective protection for the specimens, resulting in the increase of corrosion rate. 20