The localized corrosion susceptibility of different Al-Li-Cu and Al-Li-Mg-Cu alloys were studied. Tests were conducted in various concentration of NaCl, pH and temperature under alternate immersion and constant immersion conditions. The alloys were tested in all tempered conditions underaged, peak aged and overaged, resulting in significant microstructural differences caused by the different precipitation of phases.

All alloys show surface pitting and subsequent intergranular corrosion, while in presence of tensile applied stress, intergranular stress corrosion becomes evident. The overaged temper condition shows less susceptibility and slower crack growth. The results, supported by relevant fractographic and chemical analysis, determine the dominant corrosion mechanisms.

The mechanisms for the initiation of localized corrosion are based on the solution chemistry inside the restricted geometries, acidic model and basic model were formulated for the corrosion process.

Addition of inhibitors to maintain pH of the solution constant everywhere and facilitate film repair can stop localized corrosion but blistering in Al-Li based alloys may ensue.

Subject
Pits, Materials, Intergranular stress corrosion cracking, Corrosion rate, Sodium chloride, Corrosion attacks, Sodium chloride solution, U bends, Pitting, Localized corrosion, Aluminum alloys, Alloys, Corrosion potential
© 1988 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).
1988
Association for Materials Protection and Performance (AMPP)
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