Steel sheets coated with hot-dip aluminum, zinc, and a series of binary aluminum-zinc alloys have been tested for corrosion resistance in marine, industrial, and rural environments for twenty years. The results of these tests show that, compared to zinc coatings, a 55% Al-Zn alloy coating is several times more durable. Compared to aluminum coatings, the 55% Al-Zn coating provides superior galvanic protection in industrial and rural environments, and has much better resistance to crevice corrosion in marine environments. These tests demonstrate conclusively that, among alloy coatings within the Al-Zn binary system, the 55% Al-Zn alloy coating provides the best combination of durability and galvanic characteristics for long-term corrosion protection of sheet steel.

55% Al-Zn alloy coatings produced on a large-scale commercial coating line exhibited greater durability than those produced earlier on a pilot laboratory facility. This difference is attributed to decreased corrosivity of the test environments and to improvements in the coating process. These improvements include faster cooling of the coating during solidification and application of chromate passivation.

Subject
Zinc rich coatings, Marine environments, Coatings, Aluminum, Galvanized coatings, Commercial alloys, Steel, Maritime, Corrosion protection, Corrosion resistance, Zinc, Aluminum alloys, Sacrificial protection
© 1987 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).
1987
Association for Materials Protection and Performance (AMPP)
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