The search for new commercial oil production has lead to exploration for the first offshore fields within the arctic circle. The protection of structures capable of withstanding sea ice flows of 4 metres (12 feet) in thickness present the corrosion engineer with a new challenge.

The design considerations for an external corrosion prevention system on a permanent caisson structure (Molikpaq) deployed for a 20 year service life are reviewed both in terms of the cathodic protection requirement and the mechanical considerations.

A practical system adopted as a solution to these challenges is described. The rationale for selecting the maximum current output for the system, materials for anodes, dielectric shields and reference electrodes is detailed, along with the methods employed in installation.

Included is data obtained during commissioning of the system as well as values of output current and potential from the fixed control electrodes during the initial month of operation of the system with the drilling unit located offshore.

Besides achieving protection of the external immersed surfaces the system also achieved full cathodic protection in the central core area filled with aggregate.

Subject
Electric current, Steel structures, Water, Materials, Offshore structures, Cathodic protection, Installation, Cables, Hull, Steel, Impressed current, Electrodes, Anodes
© 1988 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).
1988
Association for Materials Protection and Performance (AMPP)
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