Pitting corrosion behavior of Al-Li alloys

The effect of aging on the pitting corrosion behavior of three Al-Li-Cu-(Mg)-Zr alloys (2090, 8090 and 8091) was studied. The pitting potentials of these alloys are dependent on Cu content, becoming positive with increasing Cu content. The alloys in the underaged condition are susceptible to intersubgranular corrosion due to the preferential pitting dissolution of the Cu depleted zone formed along the subgrain boundaries. The susceptibility to intersubgranular corrosion of the alloys aged for 86.4ks at 443K is ranked in the order of 8091>8090>2090. The alloy 2090 is apt to lead a general corrosion due to the dimple type pitting corresponding to T1 precipitates in the grain interiors. The pitting corrosion behavior of these alloys is closely related to the morphology of the precipitate phases of T1 and S'.