Corrosion of the Heat-Affected Zones (HAZs) of API-X100 pipeline steel in dilute bicarbonate solutions at 90°C -An electrochemical evaluation

This research explores for key correlations between the microstructures of API-X100 steel HAZs, simulated by Gleeble thermal cycles, and their electrochemical corrosion behavior in dilute bicarbonate solutions at 90. °C. The potentiodynamic polarization revealed the role of ferrite of a HAZ cooled at 10. °C/s with the lowest passive currents, and those of acicular ferrite and martensite of the 30 and 60. °C/s HAZs with unstable, thin passivation. The 0.5. V vs. SCE potentiostatic currents suggested also a slow passivation growth, of repetitive breakdowns and repassivations, for the 30 and 60. °C/s HAZs. EIS equivalent circuits and time-dependent interfaces were proposed for each of the HAZ microstructures.