Stress Corrosion Cracking of X80 Pipeline Steel Under Various Alternating Current Frequencies in High-pH Carbonate/Bicarbonate Solution

The effect of various alternating current (AC) frequencies on stress corrosion cracking (SCC) behavior and mechanism of X80 pipeline steel was investigated in high-pH carbonate/bicarbonate solution by polarization curves and slow strain rate tensile tests. With decreasing AC frequency, the passivity of the steel degrades and the SCC susceptibility increases, especially at the low-frequency AC of 30 Hz. With or without various AC frequencies, the difference in the SCC behavior and mechanism of the steel in the solution is remarkable. In the absence of AC superimposition, the crack is intergranular and the SCC mechanism is anodic dissolution. In contrast, under various AC frequencies, the fracture mode is transgranular, and the mechanism is controlled by anodic dissolution and hydrogen embrittlement.