Effects of Potential on Stress Corrosion Cracking of X80 Steel in Yumen Simulated Soil Solution
CHENG Yuan1,2, YU Hong-ying2, WANG Ying1,2, SUN Dong-bai1,2
1. National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083, China;
2. Corrosion and Protection Center, University of Science and Technology Beijing, Beijing 100083, China
Abstract：The stress corrosion cracking (SCC) susceptibility of X80 pipeline steel was investigated in simulated soil solution using slow strain rate tensile (SSRT) tests. Based on the alkaline soil in Yumen, the effect of potential on SCC was analyzed. Fracture surfaces and secondary cracks morphologies were observed using scanning electron microscopy (SEM). The results show that, there are low SCC susceptibilities at anodic potential. Anodic dissolution at higher anodic potential restricts the SCC. At lower anodic potential and OCP, anodic dissolution is weak. The difference of dissolution between crack tip and other surfaces exist. These facts benefit the crack propagation. Nevertheless, there are not enough time for the effective growth of the cracks because of slow dissolution rate and relative high strain rate. Therefore, the SCC susceptibilities are also low. When the cathodic potential is applied, anodic dissolution at the crack tip and cathodic reaction happened on other surfaces is restrained. This difference of dissolution increases the SCC susceptibility. When the cathodic potential decreases, more and more hydrogen affects the initiation and growth of crack. The SCC susceptibility increases with the decreasing of cathodic potential.
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