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.