This paper describes experimental tests with coated specimens in slow flowing natural seawater at 50C and 200C polarized to -1000, -1500 and -2000 mV SCE. One test in 3.5% NaCl solution was also executed for comparison. Coated specimens with artificially made coating damage were exposed during the tests that lasted for 30 days. During the tests the current density requirements to the specimens were continuously measured. At the end of each test the surface of the test specimens were examined to qualitatively describe the calcareous deposit developed. The tendency to cathodic disbonding (coating breakdown) was also examined at the end.

One main conclusion from the work is the high current density requirements at -1500 and -2000 mV SCE that was measured at the end of the test periods. According to the results the cathodic hydrogen reduction reaction follows a Tafel curve with a slope in the region 100 – 180 mV/decade in line with what has been reported in the literature.

The preferred solution for an Floating Production Storage and Offloading (FPSO) unit that operates 10-15 years on a field without any coating maintenance is to combine protective coating with galvanic anodes.

Subject
Coatings, Impressed current cathodic protection, Cathodic protection, Reference electrodes, Seawater, Coating damage, Current densities, Floating production storage and offloading units, Corrosion protection, Deposit corrosion, Protection potential, Calcareous deposits, Electrode potential
Keywords:
Corrosion protection, coating degradation, over protection, Impressed Current Cathodic Protection, galvanic anodes, current density requirement, calcareous deposit
© 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)
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