Study of aging and electrochemical behaviour of AlLiCuMg alloys

Aging study of 1441 and 8090 AlLiCuMg alloys exhibited characteristic precipitation hardening phenomena. Potentiodynamic polarisation studies carried out on various tempers of the 1441 and 8090 AlLiCuMg alloys in 3.5% NaCl, with a small amount of H2O2, and in 3.5% NaCl solution with pH 10 and 12 showed the shifting of open circuit potential (OCP) towards more negative potential and higher corrosion rate, with the increase of aging time. The OCP value has shifted anodically with addition of H2O2 in 3.5% NaCl solution. Further, passivity phenomenon has been observed for all the alloy tempers in 3.5% NaCl solution at pH 10 and 12. The observation of OCP shift towards more negative potential and the higher corrosion rate with the increase of aging time has been attributed to the presence of higher amounts of anodic δ (AlLi), S′ (Al2CuMg) and T1 (Al2CuLi) phases, studied by TEM, XRD and DSC methods.