Carbon dioxide corrosion is one of important degradation mechanisms for carbon steels in the oil sands oil and gas industries. Such type of corrosion has attracted considerable attention due to the increased tendency to inject CO2 into oils wells to reduce the viscosity of oil for increased production. In oil and gas production O2 contamination can occur trace amounts of aqueous O2 can cause an increase in corrosion rates normally when erosion is also involved the synergy of corrosion and erosion can significantly accelerate the failure of steels. The role of O2 in CO2 corrosion was investigated using linear polarization resistance (LRP) potentiodynamic sweeps electrochemical impedance spectroscopy (EIS) scanning electron microscopy (SEM) energy dispersive spectroscopy (EDS) and infinite focus microscopy (IFM) techniques. Efforts were made to understand the effect of O2 on corrosion and erosion-corrosion behavior of N80 carbon steel.Keywords: N80 steel CO2 corrosion O2 erosion-corrosion EIS.