EXFOLIATION CORROSION BEHAVIOR OF T6 TREATED 2090 Al-Li ALLOY IN EXCO SOLUTION AND EIS DURING EXFOLIATION CORROSION EVOLUTION
T6态2090 Al-Li合金在EXCO溶液中的剥蚀行为和剥蚀发展过程中的电化学阻抗谱

Electrochemical impedance spectroscopy (EIS) and in situ microscopic image of T6 peak-aged AA2090 Al-Li alloys in EXCO solution were studied. The localized corrosion form of the alloy during immersion evolved from pitting through intergranular corrosion, exfoliation corrosion (EC) to post EC. EC initiated at big corrosion pits which were formed with inclusion phase as center in pitting stage. The EC blisters propagate from these big pits till the upper layer is totally lifted. EIS of the initiation stage of pitting corrosion consists of a high frequency capacitive arc and a middlelow frequency inductive arc, and the inductive arc tends to disappear when pitting corrosion starts to propagate. In the intergranular corrosion stage, the second time constant corresponding to the corroded area can hardly be distinguished in the capacitive part of the EIS. In the stages of EC propagation and post EC, their EIS consist of two capacitive arcs.