Corrosion and Stress Corrosion Properties of Damage Tolerant Aluminium-Lithium Sheet Materials (NLR Contribution to BREU 3250, Task 2)

摘要

Corrosion tests under MASTMAASIS test conditions and alternate immersion constant load stress corrosion tests in a 3.5% NaCl solution were carried out on 1.6 mm thick sheet material of the Al-Li alloys 2091-T84 and 8090-T81, and on the reference 2024-T3 alloy. Corrosion tests were also carried out on preproduction 2091 sheet. The results of the corrosion tests were compared with those from additional NLR tests under different environmental conditions. It was found that exfoliation corrosion and stress corrosion did not occur in the 2091-T84 alloy. Exfoliation corrosion did occur in the preproduction 2091 sheet, and the severity of attack was much greater than that for the later 2091-T84 alloy. The 8090-T81 alloy was susceptible for exfoliation corrosion as well as to stress corrosion. Different conditions of MASTMAASIS testing (different cabinet temperatures and wet or dry bottom) classified the exfoliation resistance of the materials in approximately the same way; furthermore, the attack was generally representative for the attack in a natural environment. It was found that MASTMAASIS testing at 49 degrees C with dry or wet bottom during at least 4 weeks is the most appropriate corrosion test method.