THE INFLUENCE OF AGING AT 180-DEGREES-C ON THE CORROSION BEHAVIOR OF A TERNARY AL-LI-ZR ALLOY

The influence of aging at 180 degrees C on the corrosion behaviour of an Al-1.5%Li-0.1%Zr alloy has been studied using weight loss, open cir cuit potential (OCP) measurements and potentiodynamic polarization mea surements in 3.5% NaCl solution. Corrosion rates obtained from weight loss and I-corr values decreased for samples aged up to 6 h at 180 deg rees C whereas I-corr increased for samples aged for longer times. Val ues of OCP and pitting potential initially shifted in the noble direct ion and then towards more active values. This change in OCP was observ ed on samples that had been aged for 20 h while in the case of pitting potential an aging time of only 6 h was required. The overall change in passive current density was small, although at longer aging times ( > 40h) it showed an increase. As the amount of lithium depletion incre ased, OCP and pitting potential shifted in the active direction while passive current density showed an increase. The results have been inte rpreted in terms of the microstructure.