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 circuit potential (OCP) measurements and potentiodynamic polarization measurements 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 degrees C whereas I-corr increased for samples aged for longer times. Values of OCP and pitting potential initially shifted in the noble direction and then towards more active values. This change in OCP was observed 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 increased, OCP and pitting potential shifted in the active direction while passive current density showed an increase. The results have been interpreted in terms of the microstructure.