Effect of AC current density on stress corrosion cracking behavior of X80 pipeline steel in high pH carbonate/bicarbonate solution

Stress corrosion cracking (SCC) behavior of X80 pipeline steel under the interference of various AC current densities was investigated in concentrated carbonate/bicarbonate solution by electrochemical measurements, immersion tests and slow strain rate tensile tests. A superimposed AC shifts the corrosion potential negatively and degrades the passivity of the steel. With the increase of AC current density, the corrosion rate of steel increases. At the short term effect of AC interference, the SCC cracks are intergranular and the SCC mechanism is anodic dissolution for steels with or without the application of AC. AC superimposition increases the SCC susceptibility of steel in carbonate/bicarbonate solution. The AC current density of 30A/m2is a critical value, above which the SCC susceptibility increases.