Title
Outdoor corrosion testing of aluminium-lithium alloys
Author
Schra, L.
't Hart, W.G.J.
Boogers, J.A.M.
Institution
National Aerospace Laboratory NLR
Date
1990-08-01
Abstract
Outdoor corrosion and stress corrosion tests were conducted on Al-Li plate and sheet materials for 3 and almost 5 years respectively. The results can be summarized as follows: Corrosion: Peak aged XXXA-T651 (8090-T651) exhibited greater exfoliation corrosion resistance than 2024-T351 and 2324-T39 plate. 2091-T3 and 2024-T3 sheet were found to be unsuspectable to exfoliation corrosion. The exfoliation susceptibility of 2091 increased with increased ageing. 8090-T8 sheet showed blistering rather than exfoliation corrosion. The exfoliation attack of the plate material was generally much more severe than that of the sheet material. The MASTMAASIS test seems to be most promising for predicting the exfoliation corrosion resistance of Al-Li alloys in natural environments. There is a need for a simple and rapid immersion test, because the EXCO test proved to be unreliable for characterizing the exfoliation susceptibility of Al-Li alloys. Stress corrosion: The SSC initiation resistance of XXXA-T651 plate was similar to or slightly better than that of 2024-T351 and 2324-T39 plate. For SSC growth the ranking of materials depended on the influence of corrosion product wedging (CPW) on SCC growth. When the influence was small, as in the first 1½ years of testing, 2024-T351 and 2324-T39 exhibited slower crack growth; whereas XXXA-T651 was superior when there was a significant influence, as in the latter part of testing. Alternate immersion SCC initiation testing in synthetic seawater resulted in the same trends as outdoor exposure. SSC growth in laboratory test environments was greatly influenced by CPW.
Subject
accelerated life tests
aluminium alloys
lithium alloys
corrosion tests
stress corrosion cracking
exposure
salt spray tests
aging (metallurgy)
corrosion resistance
crack propagation
stress intensity factors
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Publisher
Nationaal Lucht- en Ruimtevaartlaboratorium
Access restriction
Campus only
Source
NLR Technical Publication TP 90272 U
Part of collection
Aerospace Engineering Reports
Document type
report
Rights
(c) 1990 National Aerospace Laboratory NLR