Stress corrosion cracking behavior of 35CrMo steel in acidic hydrogen sulfide solutions

The combination of electrochemical corrosion technologies were performed to study corrosion of 35CrMo steel in H₂S solution with various pH values by simulate the low concentrations of hydrogen sulfide environment of oilfield in the pit. Stress corrosion cracking (SCC) of 35CrMo steel in acidic hydrogen sulfide solutions with various pH values and temperature was investigated by U-bent specimen immersing test and slow strain rate tensile test. It is shown that 35CrMo steel exhibits a high susceptibility to SCC in acidic hydrogen sulfide solutions. The susceptibility and corrosion increases by decreasing the pH value of the solution. The susceptibility varied seriously with the change of pH value. The decrease of pH would accelerate the cathodic process greatly, leading to the increase of corrosion rate and hydrogen charging current density, resulting the local anodic dissolution and hydrogen embrittlement effect more significant. The different susceptibility to SCC of 35CrMo steel in 15-90°C, Maximum susceptibility in 35°C and 90°C. The SCC mechanism of 35CrMo steel is hydrogen embrittlement (HE) mainly and combination of anodic dissolution (AD) in acidic hydrogen sulfide solutions.