Laboratory study using a specially designed circulating test rig was carried out to investigate the effectiveness of achieving complete cathodic protection of UNS NO44001 heat exchanger tubes in seawater applications. Cyclic polarization of the UNS NO4400 alloy tube material was conducted to determine the pitting and repassivation (protection) potentials prior to the galvanic coupling study. The parameters studies include the potential-time relationship of uncoupled and coupled steel to UNS NO4400 alloy tubes, effect of anode size, galvanic current distribution, effect of water flow direction and galvanic potential distribution at different tube lengths. The results indicated that sufficient sacrificial protection can be achieved to prevent pitting corrosion of UNS NO4400 alloy tubes when coupled to steel anodes in flowing seawater environment.

Subject
Noble potential, Galvanic anodes, Cathodic protection, Tubes, Free corrosion potential, Seawater, Steel, Pitting, Galvanic current, Alloys, Protection potential, Corrosion potential, Electrode potential
Keywords:
Galvanic Coupling, Heat Exchanger, Carbon Steel, UNS NO4400 Alloy Tubes and Seawater
© 1995 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).
1995
Association for Materials Protection and Performance (AMPP)
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