The electrodeposition of double-layer nickel coatings has found widespread applications in the automobile industry(1). The composite coating consists of an initial layer of levelling, semibright nickel (sulfur-free) followed by a bright nickel layer. A final flash coating of chromium is normally applied to overcome the tendency for nickel to tarnish during environmental exposure. The bright nickel layer contains small quantities (0.05 to 0.08 percent) of sulfur (originating from the brightening agent) and, in a chloride environment, is more active in electrode potential than the semibright layer(2) and thus tends to protect sacrificially the semibright layer from attack. The result is a decreased tendency for corrosive penetration of the coating to the basis metal, and the double-layer nickel thus provided greater protection than the same thickness of single-layer nickel deposits.

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Army equipment is required/function effectively in a wide variety of environments; therefore it is necessary to provide adequate protection against corrosion of the various components. Protection of steel components in tropical environments has been particularly important in view of the military activities in tropic and semi-tropic regions. Consequently, it was considered important to ascertain the effectiveness of single and double-layer nickel deposits for providing corrosion protection to steel exposed to tropical environments.

Subject
Nickel coatings, Steel panels, Marine environments, Top coats, Chromium, Corrosion attacks, Metals, Steel, Corrosion protection, Wind, Deposit corrosion, Nickel, Electroless nickel
© 1971 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).
1971
Association for Materials Protection and Performance (AMPP)
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