Corrosion of an Advanced Al-Cu-Li Alloy for Aerospace Applications

Abstract:

This paper discusses two Al-Cu alloys for aerospace applications, one which has a high concentration (>1.8 wt.%) of Li. These alloys are AA2024-T3 (Al-Cu) and AA2099-T8E77 (Al-Cu-Li) and are both in the plate format. Anodic polarisation and immersion in a 3.5 wt.% NaCl solution have been carried out and a comparison of the corrosion mechanisms have been made. Both alloys showed extensive corrosion over the surface, AA2024-T3, however, had areas of pitting that had joined together forming large corrosion regions, whereas AA2099-T8E77 had numerous corrosion pits that had not merged. The pits on AA2099-T8E77 propagated to a depth ~120 µm whereas on AA2024-T3 the maximum depth was ~85 µm. Intergranular and transgranular corrosion was also observed on the AA2024-T3 alloy following anodic polarisation. AA2099-T8E77 had reduced corrosion resistance with regards to E_pit-E_corr values. For both alloys, dissolution of matrix material surrounding the Cu-rich intermetallic particles was observed, highlighting the particles’ cathodic nature.

• Periodical: Materials Science Forum (Volume 765)
• Pages: 629-633
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.765.629
• Online since: July 2013
• Authors: David M. Carrick, Simon Hogg, Geoffrey D. Wilcox
• Keywords: Aluminium Alloy, Anodic Polarisation, Copper, Corrosion, Lithium

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