Effect of applied potentials on stress corrosion cracking of X70 pipeline steel in alkali solution

Stress corrosion cracking (SCC) behavior of X70 pipeline steel in alkali solution at different applied potentials was investigated using slow strain rate testing (SSRT). Morphology of X70 pipeline steel fracture surface at different applied potentials was observed by scanning electron microscope (SEM). The results showed that X70 pipeline steel was susceptible to SCC in alkali solutions. It was found that low potentials applied increased susceptibility to SCC at open circuit potential (OCP). The fracture mechanism followed anodic dissolution mechanism of SCC. The precipitation of hydrogen increased hydrogen diffusion into the metal, hence increased susceptibility to SCC under higher cathode potential in alkali solution. The fracture followed hydrogen induced cracking mechanism.