Effects of Alternating Stray Current on Corrosion Behavior of X80 Pipeline Steel

Weight loss test of X80 pipeline steel samples was performed in soil simulated solutions at various AC current densities from 0 to 200 A/m2.The microstructure of X80 pipeline steel after corrosion,the surface appearance,structural composition and phase constitution of corrosion products were studied by SEM,EDS and XRD analysis techniques.The results showed that the corrosion rate of X80 pipeline steel increased first slowly and then rapidly,at last the increase tendency slowed down and would not be unlimited increase as AC current density increased.The corrosion product was divided into two layers.The outer layer was a kind of porous structure and consisted of red-brown Fe2O3 and yellow-brown FeOOH.The inner layer was a kind of dense structure and consisted of black Fe3O4.At a low AC current density,uniform corrosion occurred,while at a high AC current density,pitting corrosion occurred extensively on the X80 pipeline steel sample surface.