Growth behavior and mechanism of stress corrosion cracks of X80 pipeline steel in simulated Yingtan soil solution

Stress corrosion cracking (SCC) in soil environments is one of the major failure and accident causes for oil and gas pipelines, which have induced hundreds of damages all over the world, resulting in serious economic losses and casualties. Previous study showed that acidic soil environments in Southeast of China are highly sensitive to SCC of pipeline steels. However, there is less research on the behavior and mechanism of growth behavior of SCC in this environment up to date. SCC behavior and mechanism of X80 pipeline steel in the simulated solution of Yingtan in China was investigated with electrochemical polarization curves, EIS, slow-rateloading crack-growth test and SEM. Results showed that the applied polarization potential played an important role in SCC growth behavior and mechanism of X80 pipeline steel in the simulated solution of the acid soil environment. With the decreasing of the applied potential, the crack propagation rate increased constantly. In comparison to the crack propagation at the open circuit potential, the cracks extended faster in the initial stage of crack propagation when the applied potential was -850 mV; nevertheless, in the rapid propagation stage, the rate of the propagation was magnified with the application of -1200 mV potential. In addition, the crack propagation mode varied with applied potentials: it was mixed-controlled by both anodic dissolution (AD) and hydrogen embrittlement (HE) when the applied potential was more positive than -930 mV, and only in control of HE when the potential was less than -930 mV.