ISO INTERNATIONAL STANDARD 11474 First edition 1998-03-15 Corrosion of metals and alloys Corrosion tests in artificial atmosphere Accelerated outdoor test by intermittent spraying of a salt solution (Scab test) CorrosiondesmetauxetalliagesEssaisdecorrosionenatmosphere artificielle Essai de corrosion accélére en extérieur par vaporisation intermittente d'un brouillard salin (Scab test>) Reference number ISO 11474:1998(E) Not for Res-ale ISO 11474:1998(E) Foreword IsO (the International Organization for Standardization) is a worldwide federation of national standards bodies (IsO member bodies). The work of preparing International Standards is normally carried out through isO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non- governmental, in liaison with iSO, also take part in the work. IsO collaborates closely with the International Electrotechnical Commission (lEC)onallmattersofelectrotechnicalstandardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard ISO 11474 was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys. Annex A of this International Standard is for information only. @ISO1998 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International OrganizationforStandardization Casepostale56·CH-1211Geneve20Switzerland Internet central@isocs.iso.ch X.400 C=ch; a=400net; p=iso; 0=isocs; S=central Printed in Switzerland from IHS Not for Resale ISO 11474:1998(E) @ ISO Introduction Corrosion testing under atmospheric exposure conditions IS smost commonly executed as field tests. As the corrosion rate depends on the environment of the test site, the latter should ideally be selected to best represent the environments in which the material is likely to be used. The results of field tests cannot therefore be usedtopredict service performance exactly but they do provide the best guidance to service performance. Field tests, however, may require exposure periods corresponding to the expected service life of a material. To promote corrosion and accelerate the degradation process, test sites with a high atmospheric corrosivity can be used. Such test sites may be To increase the corrosion rate at other test sites, artificial measures need to be adopted. In the method described, the corrosion process during outdoor exposure is accelerated by intermittently spraying a solution of sodium chioride (mass fraction 3 %) on to the test surface thus simulating and enhancing the environmental stress prevailing at marine test sites. The method is mainly intended for comparative testing and one or more reference materials are therefore always necessary. The results obtained do not permit any more far-reaching conclusions on the corrosion resistance of the tested metal in all environments in which it may be used. The method described can nevertheless give valuable information on the relativeperformanceofmaterialsinservice. NOTE - The title of this International Standard presents (within parentheses) a common name for this kind of test. Hitherto, “scab test" has been used mainly in a narrower sense to denote similar test methods developed within the car industry for the study of underfilm corrosion, particularly where painted steel surfaces have been locally damaged by stone shots. The word "scab" is no acronym. It simply refers to a well-known but not very pleasant disease and its symptom, i.e. a kind of crusty spots on the skin. Inthis International Standard