Studies were carried out to evaluate the stress corrosion cracking (SCC) behavior of a X-70 microalloyed pipeline steel, with different microstructures by means of the slow strain rate testing (SSRT) technique at 50 °C. Tests solutions consisted of 0.1, 0.05, 0.01 and 0.005 M sodium bicarbonate (NaHCO3) with KCl, CaCl2 and MgSO4-7H2O additions. Different anodic and cathodic potentials were applied. Additionally, experiments using the SSRT technique but with pre-charged hydrogen samples and potentiodynamic curves at different sweep rates were also done to elucidate hydrogen effects in this type of steel. The results showed that the different microstructures in conjunction with the anodic applied potentials shift the cracking susceptibility of the steels evaluated. On the other hand the closest cathodic potentials to their respectively steels rest potentials lower SCC susceptibility no matter the microstructure being tested. Contrary to this behaviour higher cathodic potentials promote SCC in all steel conditions. The fracture mechanisms actuating on the SSRT samples were promoted by anodic dissolution and protective film rupture. The results at different sweep rates indicate that certain microstructures are more susceptible to present anodic dissolution corrosion mechanism. Meanwhile more concentrated solution promotes ductile (no brittle) fracture surfaces on SSRT specimens.

Subject
Water, Intergranular stress corrosion cracking, Anode potential, Cathodic potential, Microstructure, Pipelines, Dissolution, Polarization curves, Steel, Risk reduction, Heat treatment, Stress corrosion cracking, Hydrogen
Keywords:
SCC, microalloyed pipeline steel, diluted NaHCO3 solutions, SSRT technique
© 2008 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2008
Association for Materials Protection and Performance (AMPP)
You do not currently have access to this content.