The current density requirements for the laboratory polarisation of bare steel, bronze and painted steel in seawater have been examined at a potential of −800mV (SSC). Flow at velocities up to 3.0 m s−1 markedly increased demand with the bare alloys, with a greater effect upon polished specimens than upon aged. The beneficial effect of chalking deposits was evident under flow but not in static seawater. Propeller rotation increased protection requirements, particularly for a bright surface, although to a lesser extent than with flow. From the experimental and ship data it would appear that the majority of the effect of flow and under way conditions occurs within approximately the first 2.5 m s−1 (5 knots). The requirement for standardisation of techniques for determining protection current density requirements is identified. Results are discussed in relation to the need to install ICCP systems with a current output capacity sufficient to meet maximum anticipated demand and to define the requirements of individual zones.

Subject
Electric current, Propellers, Impressed current cathodic protection, Cathodic protection, Seawater, Bronze, Hull, Current densities, Steel, Marine vessels, Deposit corrosion, Alloys, Chalking
Keywords:
Cathodic protection, current densities, ships, flow, propellers, chalking, design, system capacity
© 1994 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).
1994
Association for Materials Protection and Performance (AMPP)
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