The relative tendency of pipeline girth weld coatings to shield cathodic protection (CP) current was studied in the laboratory. Four types of liquid coatings: epoxy, epoxy polyurethane, polyurethane, and wax were investigated, with fusion bond epoxy (FBE) and a polyethylene shrink sleeve used for comparison. The results showed that the liquid coatings, when applied extra thin to accelerate the kinetics of absorption and current transmission, all disbonded by blistering, and all allowed CP current to be transmitted. For all coatings, micro-defects were found to be associated with the blisters, and it is believed that these defects were necessary to allow effective CP under disbonded coatings.

Subject
Holidays, Electrochemical impedance spectroscopy, Thin films, Liquid coatings, Water, Coatings, Cathodic protection, Water absorption, Fusion bonded epoxy coating, Polyurethane coatings, Shielding, Electrochemical data, Blistering
Keywords:
coating, CP shielding, EIS, blistering
© 2006 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).
2006
Association for Materials Protection and Performance (AMPP)
You do not currently have access to this content.