Abstract: The electrochemical corrosion behavior and mechanism of original state (welded state) and tempered state (650 ℃ for 3 h) X80 pipeline steel were investigated in a simulated solution of northwest saline soil by using electrochemical measurements,SEM,EDS and XRD.Effects of anneal treatment and corrosion time on the polarization curves were anlyzed.The results show that the change of microstructure caused the corrosion resistance of annealed state X80 pipeline steel was far lower than that of original state.The corrosion tendency both first increased and then decreased with the increasing corrision time.The corrosion rates first,decreased then increased,but the general corrosion rates and pitting sensitivity for both original and heat-treated steels increased with increasing exposure time.The cathodic process was dominated by the oxygen activation control.The corrosion product consisted of FeOOH (surface layer) and Fe3O4 (inner layer).The content of Cl- dominated the corrosion severity.