Effect of Rust Layer on Corrosion Behavior of X80 Pipeline Steel in Yingtan Soil Simulated Solution

A rust layer was obtained by X80 steel immersed in Yingtan soil simulated solution for 7 days, the surface morphology of the rust was analyzed by SEM, and the electrochemical behaviors of X80 bare steel and X80 steel with rust layer were investigated by polarization curves and EIS. The SEM results show that the rust layer was formed uniformly on the surface, however, it was loose and porous. Electrochemical experiments show that the free corrosion current density of X80 steel with rust was higher than that of X80 bare steel, and the charge transfer resistance of the former was lower than that of the latter. It was due to the increase of the real electrode area for the electrode reaction of X80 steel resulted from porous rust. Therefore, the short-term rust on the X80 steel could not protect the X80 steel from corroding.