A number of investigations exploring the causes of autobody steel corrosion have been reported (1-5). These studies generally agree that poor corrosion resistance to salt-fog exposure occurs when an excessive amount of carbonaceous contamination is present on the steel surface. Other work indicates additional chemical elements other than carbon may also be responsible for poor corrosion resistance (6). Specific practices during annealing at the steel mill have been pointed to as the source of the carbon deposit. This surface carbon layer is not removed by the standard alkaline cleaning pretreatment applied as the first step in the zinc phosphate conversion coating of autobody steel. Recent work at 3M Laboratories has shown that abrasive brushing of steel, as currently practiced in the making of Zincrometal (7,8), uniformly removes about O.5μm of the steel surface thereby eliminating the detrimental carbonaceous deposit. Elimination of the carbon layer by this means results in a decided improvement in the steel’s corrosion resistance (9).

Subject
Acids, Zinc rich coatings, Steel surfaces, Water, Abrasion, Abrasives, Preconditioning, Phosphates, Salt spray corrosion testing, Steel, Carbon, Zinc, Cleaning
© 1981 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).
1981
Association for Materials Protection and Performance (AMPP)
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