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 (c) thermal cycles, and their electrochemical corrosion behavior in dilute bicarbonate solutions at 90 degrees C. The potentiodynamic polarization revealed the role of ferrite of a HAZ cooled at 10 degrees C/s with the lowest passive currents, and those of acicular ferrite and martensite of the 30 and 60 degrees 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 degrees C/s HAZs. EIS equivalent circuits and time-dependent interfaces were proposed for each of the HAZ microstructures. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.