Mechanism of perforation corrosion on vehicles in the area where deicing salts are dispersed on road in winter was investigated, using the Gumbel probability plots of the maximum depth of corrosion inside the lapped portion and quantitative analyses of crystalline compositions of the iron rusts which formed on the steel panels of vehicles. It was estimated that perforation occurred in 7 years for zincrometal steel sheet and more than 14 years for galvanized steel sheet with zinc coating weight of 120g/m2 in the crevice of lapped panel. The composition of the rust in the lapped portion of galvanized steel panels was mainly amorphous at the initial stage of corrosion and moves towards the high content of (γ-FeOOH+Fe3O4) regions of the non-galvanized parts. Zinc corrosion product prevented the redox reaction of the iron rust and performed as corrosion inhibitor of steel in laboratory simulation tests. Perforation mechanism on vehicles in real environments will be also discussed in the following stages; (i) corrosion of zinc layer, (ii) galvanic corrosion of zinc, (iii) corrosion of steel under zinc corrosion product, (iv) corrosion of steel.

Subject
Zinc rich coatings, Composition, Perforation, Rolled steel, Iron, Corrosion products, Steel sheet, Crevices, Galvanized steel, Steel, Rust, Zinc, Coating vehicles
Keywords:
automotive corrosion, perforation, cosmetic corrosion, galvanized steel sheet, iron rust
© 1998 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).
1998
Association for Materials Protection and Performance (AMPP)
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