Corrosion evolution and stress corrosion cracking of E690 steel for marine construction in artificial seawater under potentiostatic anodic polarization

摘要

In the present work, corrosion evolution and stress corrosion cracking behavior of E690 steel for marine equipment and construction under potentiostatic anodic polarization are investigated via electrochemical analysis, morphology and topography observation and slow strain rate tensile tests. Positive shift of anodic potential accelerates the two dissolution stages including electrochemical oxidation from Fe to Fe2+ and Fe2+ to Fe3+ of E690 steel. Composition of corrosion products is not altered by anodic polarization but the rust layer morphology and structure are changed. Pitting corrosion initiated around complex oxide inclusions and its transformation to uniform corrosion dominates the corrosion evolution process at OCP, while local acidification induced corrosion pits beneath thick and cracked rust layer dominates the localized corrosion under strong anodic polarization. The SCC susceptibility of E690 steel increases with the positive shift of applied anodic potentials, attributed to the acceleration of anodic dissolution (AD) effect under weak anodic polarization and synergistic effect of AD and hydrogen embrittlement (HE) under strong anodic polarization. (C) 2019 Elsevier Ltd. All rights reserved.