The purpose of this paper is to clarify the influence of the cathodic polarized potential on the stress corrosion cracking (SCC) susceptibility of X120 steel in a simulated acidic soil solution and the different SCC mechanisms at different cathodic polarized potentials.
The SCC behaviors of X120 pipe steels at various potentials were investigated in a simulated acidic soil solution by slow strain rate tensile tests, electrochemical impedance spectroscopy and surface analysis techniques.
The fracture surface of X120 steel stretched in air showed a ductile fracture. Both elongation and tensile strength of X120 steel in the simulated acidic soil solution decreased compared to that obtained in air. A slight cathodic polarization increased the elongation and tensile strength of X120 steel; therefore, the SCC susceptibility was lower at −0.65 VSCE than that at OCP, anodic dissolution dominates the corrosion process. However, a strong cathodic polarization induced hydrogen embrittlement, decreasing elongation and tensile strength, therefore, the SCC susceptibility was highest at −1.1 VSCE, and hydrogen embrittlement became the dominant process.
The paper provides an essential insight into the mechanism of pipeline SCC for X120 steel in acidic soil environments.
