Hydrogen absorption and resultant long-term embrittlement can be a potential problem for titanium alloy offshore components which contact adjoining steel structures that are cathodically protected in seawater. Calculated potential profiles for typical uncoated titanium alloy deep-water production and drilling risers and subsea flowlines reveal that impressed CP potentials will be Cathodic (negative) to the assumed safe limit of - 800 mV vs Ag/AgCl along the entire titanium component length. Two practical strategies for preventing hydrogen damage were identified as: 1) electrical isolation rtf titanium alloys at terminal connections, and 2) application of robust, seawater-resistant polymeric OD surface coatings. Drilling risers may or may not require OD coatings depending on service requirements, whereas subsea titanium alloy tube-bundle umbilical lines are not susceptible to hydrogen damage if short end sections are coated.

Subject
Risers, Modeling, Cathodic potential, Metal surfaces, Hydrogen absorption, Flanges, Seawater, Flowlines, Current densities, Electric potential, Titanium, Titanium alloys, Hydrogen
Keywords:
Titanium, offshore applications, subsea service, cathodic protection, computer modeling, hydrogen embrittlement, mitigation
© 1997 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).
1997
Association for Materials Protection and Performance (AMPP)
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