Effect of Alternating Current on Passive Film and Corrosion Behavior of Pipeline Steel with Different Microstructures in Carbonate/Bicarbonate Solution

The relationship between microstructure and alternating current (AC) corrosion behavior of X80 pipeline steel was systematically studied in CO32-/HCO3- solution using corrosion tests and surface analysis technology. The results show that AC prevents the formation of passive film and decreases its stability. AC generates a different damage effect to the passive film on steels with various microstructures. The passive film of normalized microstructure steel has a relatively high stability, followed by the hot-rolled steel, and that of the annealed sample is the most unstable. The influence of AC on passive film of steels with various microstructures causes a difference in the corrosion resistance. The corrosion form of steels with different microstructures applied with AC displays the obvious characteristic of localized corrosion. The normalized microstructure has the optimum corrosion resistance, followed by the hot-rolled steel, and the annealed steel possesses the worst corrosion resistance. The difference in the AC corrosion behavior of X80 steels may be related to the microstructure.