EFFECT OF APPLIED POTENTIALS ON STRESS CORROSION CRACKING OF X80 PIPELINE STEEL IN SIMULATED YINGTAN SOIL SOLUTION

Abstract

Stress corrosion cracking (SCC) of X80 pipeline steel in a simulated solution of the acidic soil environments in Yingtan China was studied by means of potentiodynamic polarization curves, slow strain rate test (SSRT) and corrosion morphologies characterized by SEM. The results show that X80 pipeline steel has high SCC susceptibility in the simulated solution and the failure mode is transgranular cracking. The SCC mechanism would vary with the applied cathodic potential. When the applied potential is positive to about −930 mV, the SCC behavior is controlled by the com- bined effect of anodic dissolution (AD) and hydrogen embrittlement (HE), i.e. the SCC mechanism is AD+HE. However, when the applied potentials are lower than −930 mV, such as −1000 and −1200 mV, the process of hydrogen evolution plays the dominant role in SCC occurrence, meaning that the SCC mechanism is HE under such applied potentials. Moreover, SCC susceptibility increases with decreas- ing applied cathodic potential. Compared with X70 pipeline steel in acidic soil environments, HE plays a more important role in affecting SCC occurrence.