Effect of aging on the pitting corrosion behavior in Al-Li alloys

Electrochemical measurements and corrosion tests in the neutral NaCl solutions were conduced to clarify the effect of aging on the pitting corrosion behaviors in Al-2.15%Li and Al-Li-Cu-Mg-Zr (8090) alloys. In the Al-Li binary alloy, the pitting potential is more noble than that of pure aluminum except under the overaged condition. The Li addition in this extent and the precipitation of coherent δ' phase have no deleterious effect on the pitting corrosion resistance. In 8090 alloy, the pitting potential which is most noble under as-quenched condition changes systematically in the less noble direction with aging. The under-and peak-aged alloys show a certain difference in the pitting potentials corresponding to the pitting at the grain boundary and the matrix respectively, more over the former potential being less noble, and so give rise to the intergranular corrosion. The corrosion rate increases according to the precipitation of T1 or S' phase just before the peak aging.