Influence of applied potential on stress corrosion cracking behavior of X80 pipeline steel in near-neutral pH soil environments

Using slow strain rate tension (SSRT) experiment, electrochemical polarization and SEM observation, the influence of applied cathodic polarization potential on stress corrosion cracking (SCC) behavior of X80 pipeline steel is analyzed in a simulated near-neutral pH soil environment of NS₄ solution. The results show that the SCC sensitivity of X80 pipeline steel is higher in near-neutral pH soil environments, and the cracking model is transgranular SCC. SCC mechanism changes with different applied cathodic polarization potential - when the applied cathodic polarization potential is higher than ﹣900 mV, SCC is controlled jointly by anodic dissolution and hydrogen embrittlement, and when the applied cathodic polarization potential is under ﹣900 mV, SCC is controlled by hydrogen embrittlement. With the increase of negative applied potential, section shrinkage, elongation, and fracture time of slow tension specimen are reduced, and the SCC sensitivity increases, so it is necessary to avoid over-protection in actual pipeline cathodic protection.