This work focuses on the corrosion resistance of a newly developed Zn-Al-Mg alloy coating system for steel containing Zn + 2 wt.-% Mg + 2 wt.-% Al (ZM) in comparison to the conventional zinc coating (HDG). Both systems were produced via hot-dip galvanizing on a large scale plant and comprise an average coating thickness of 7 μm. The corrosion resistance was evaluated by exposure to standardized laboratory corrosion test.

Tests with and without chloride were used. In the tests with chloride addition the influence of pH value was considered as well. In chloride-free atmosphere the effect of drying and temperature changes were included in the investigation.

It could be shown that the newly developed ZM coating forms a stable, well-adherent corrosion product layer of zinc aluminum carbonate hydroxide, Zn6Al2(CO3)(OH)16·4 H2O, next to the steel substrate in all tested environments. This protective corrosion product layer is responsible for the enhanced corrosion resistance of ZM-coated steel in comparison to HDG steel.

Subject
Coated steel, Zinc rich coatings, Steel surfaces, Hydroxides, Steel substrates, Corrosion products, Salt spray corrosion testing, Steel, Rust, Corrosion protection, Corrosion resistance, Zinc, Samples
Keywords:
hot-dip galvanizing, alloy coating, Zn-Al-Mg coating, salt spray test, alternating temperature, pH value, relative humidity, drying cycles
© 2011 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).
2011
Association for Materials Protection and Performance (AMPP)
You do not currently have access to this content.