Effect of AC on corrosion behavior of X80 pipeline steel in high pH solution

Corrosion behavior of X80 pipeline steel under the application of various waveforms AC was investigated in concentrated carbonate/bicarbonate solution by electrochemical measurements, immersion tests, and slow strain rate tensile tests. Under the application of AC current of various waveforms, the corrosion potential shifts negatively and the passivity of the steel degrades severely. Superimposed AC current causes an increase of corrosion rate, and the corrosion rate of the steel under square wave is the highest, next the triangular wave, the least sine wave. The steel mainly experiences localized corrosion under various waveforms AC, in particular with the square wave AC current, the pitting occurs more apparently. AC superimposition enhances the stress corrosion cracking (SCC) susceptibility of the steel in carbonate/bicarbonate solution, especially at square wave. At a short term effect of AC interference, the fracture mode is intergranular, and the SCC behavior of steel in high pH solution is affected by the anodic dissolution for steel with or without AC application.