EIS analysis on stress corrosion initiation of pipeline steel under disbonded coating in near-neutral pH simulated soil electrolyte

•EIS is useful for mechanistic study of corrosion process under disbonded coating.•Pipeline steels under disbonded coating is in an active dissolution state.•Yield stress enhances pitting corrosion and microcracks under disbonded coating.•Corrosion rate shows a decreasing trend over distance from coating defect.•CO2 gradient is responsible for corrosion scenarios under disbonded coating.

Initiation of stress corrosion of X80 high strength low alloy (HSLA) pipeline steel in a near-neutral pH environment was investigated in a crevice cell simulating coating disbondment. Multi specimens were loaded simultaneously by a loading frame. EIS was applied to characterize behavior of SCC and local electrochemical process. Results indicate that the steel under disbonded coating is in an active dissolution state. In-depth profile of the reciprocal charge transfer resistance shows a decreasing trend over distance from the opening. A shielding factor was proposed to characterize shielding effect of disbondment on stress corrosion of pipeline steels.