Abstract: The effects of AC current density on the corrosion behavior of X65 steel in concentrated carbonate/bicarbonate solutions were studied by potentiodynamic polarization curve measurement,immersion testing and the surface characterization technique. When the AC current density increases,the passive region significantly narrows,the pitting potential negatively shifts,the passive current density increases,and the corrosion of X65 steel accelerates. At low AC current density(100 A·m^-2) the passive current density,the pitting corrosion degree and the corrosion rate slightly increase with the increasing of AC current density,but at high AC current density(≥ 100 A·m^-2),they increase rapidly.