This study evaluated the technical feasibility of applying an optimized combination of cathodic polarization (CP) and inorganic Zn coating, the two, common corrosion protection methods employed for marine structures. As an initial step to achieve this goal, batches of inorganic Zn coatings with various thickness were formed on A36 Gr. steel plates. The effects of cathodic polarization parameters, such as CP current density, potential were evaluated to establish the optimum combination to provide better corrosion resistance of the inorganic Zn coated steel plate in natural seawater. Optimum number and arrangement of CP anodes for 3-dimensional mock-up structure of ballast tank were also evaluated by using FEM analysis of potential distribution under CP, and the result was fairly consistent with the experimental data obtained from tests made on the inner surface of a box-type, mock-up structure.

It’s suggested that thicker inorganic Zn coating (about 40μm) is desirable than the conventional “shop primer” (about 10μm), whereas the current density of 0.5~1 A/m2 for CP is necessary to form calcareous deposit on the inorganic Zn coating to ensure continuous corrosion protection. Evaluation of the proposed method’s protective properties by using electrochemical techniques suggested that the combination of CP and inorganic Zn coating can be as effective as tar-epoxy in certain application areas.

Subject
Steel structures, Coated steel, Primers, Zinc rich coatings, Steel surfaces, Protective coatings, Cathodic protection, Current densities, Cathodic current density, Corrosion protection, Maintenance, Inorganic zinc rich coatings, Calcareous deposits
Keywords:
Zn-inorganic primer, calcareous deposits, cathodic protection, marine corrosion, FEM analysis
© 2002 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).
2002
Association for Materials Protection and Performance (AMPP)
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