The CO₂ corrosion behavior of N80 steel in stratum water with saturated CO₂ under tension, compression and bending stress conditions, was investigated by electrochemical impedance spectra. The results showed that the anodic impedance spectra under the three stress conditions all consisted of three time-constants, i.e., the capacitance at high frequency, inductance at middle frequency and capacitance at low frequency, among which the frequency at high frequency and the capacitance of the double-layer were related to the transfer impedance, the dissolution of N80 steel contributed to the inductance, and the capacitance at low frequency was corresponding to the formation of corrosion film on N80 surface. With the stress increment, the inductance increased, and the capacitance at low frequency decreased, meaning that the anodic reaction rate increased under the stress conditions. The cathodic impedances under the three stress conditions all consisted of capacitance at high frequency, Warburg im-pedance and capacitance at middle and low frequencies, and with the increment of strain under the three stress conditions, the Warburg impedance increased, while the reaction impedance and the capacitance of double-layer decreased, meaning that the CO₂ corrosion may be accelerated when N80 steel is under the stress conditions.

Key words: N80 steel, electrochemical impedance spectra, CO₂ corrosion, stress condition