Within the past two years bi-metallic anodes have become commercially available for offshore use. These anodes consist of a thin layer of high potential magnesium cast and anchored on to one face of an aluminum-based anode. High current output from the magnesium enables rapid polarization of the structure. Calcareous films formed on the structure during rapid polarization can significantly reduce maintenance current density requirements and the amount of aluminum anode material required for the service life of the structure. This paper presents the results of 7,000 hour field tests that were conducted to evaluate the performance of full-scale bi-metallic anodes (Mg layer on Al+In+Zn) on a deep water production jacket installed in the Gulf of Mexico. Results of current output measurements and potential measurements of the structure to reference electrodes are compared between bi-metallic anodes and aluminum anodes (Al+In +Zn) at water depths of -37.5 and -105 meters. Initial current output from the bi-metallic anodes was over double that from the aluminum anodes. The bi-metallic anodes were found to be a cost effective means to rapidly polarize a structure.

Subject
Water depth, Water, Anode potential, Magnesium anodes, Reference electrodes, Structures, Current densities, Anodic current, Magnesium, Maintenance, Jackets, Electrode potential, Anodes
© 1993 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).
1993
Association for Materials Protection and Performance (AMPP)
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