Sacrificial anode cathodic protection offers cost-effective corrosion protection of submerged marine structures. However, it should be appreciated that longevity of the protection systems can only be estimated with a limited degree of accuracy. To ensure a certain reliability, i.e. probability that a cathodic protection system will achieve its design life, some intentional overcapacity must be included in the design. In contemporary design, specific parameters are defined with an intrinsic conservatism rather than using some overall design factor. The paper discusses how design parameters should be selected to provide adequate reliability, taking account of the additional investment cost for an overcapacity which may not be utilised on the one hand, and comparing this with the potential costs associated with increased monitoring and maintenance, including subsea retrofitting of anodes, if the design capacity initially installed proves to be insufficient. A comparison is made between pertinent design parameters in DNV RP B401 (1993), NACE RP0176-94 and NORSOK M-CR-503 (1994).

Subject
Steel structures, Costs, Steel surfaces, Materials, Galvanic anodes, Reliability, Cathodic protection, Pipelines, Current densities, Anodic current, Corrosion protection, Paints, Anodes
Keywords:
cathodic protection, sacrificial anodes, seawater, marine structures, subsea pipelines, design, corrosion control, economy, cost analyses
© 1996 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).
1996
Association for Materials Protection and Performance (AMPP)
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