The Influence of Composition and Microstructure on the Corrosion Behavior of Two AlLiX Alloys

The corrosion behavior of two AlLiCuZrGe alloys, with and without Mg, was studied. The types of corrosion tests conducted included exfoliation corrosion, crevice corrosion, constant immersion studies, and anodic polarizations. The alloys were tested in both the underaged and overaged tempers, resulting in significant microstructural differences caused by the precipitation of many metastable and equilibrium phases. Magnesium addition results in a more consistent corrosion behavior with aging time, a higher rate of electrochemically induced corrosion, and the development of a type of pit not seen in the alloy without magnesium. Overaging increases the resistance to exfoliation corrosion and electrochemically induced corrosion. Both alloys exhibit good resistance to crevice corrosion. The results of this study show that lithium is not the only reactive species present in these alloys, and that in fact, the corrosion behavior of these alloys appears to be more dependent on the various precipitate phases present caused by other alloy additions.