Corrosion behavior of 2198 Al-Cu-Li alloy in different aging stages in 3.5 wt% NaCl aqueous solution

In this paper, corrosion behavior of 2198 Al-Cu-Li alloy in different aging stages is investigated using immersion and electrochemical measurements in 3.5 wt% NaCl aqueous solution. The corrosion resistance is found to decrease from the solution-anneal to the peak-aged condition but increase after the peak-aged, which is due to microstructure evolution of three main kinds of precipitating phases with the aging process: T1 (Al2CuLi), theta' (Al2Cu), and a few delta' (Al3Li) phases. The anode T1 phase grows and increases with the aging treatment and becomes nearly unchanged after the peak-aged. Moreover, the cathode theta' phase slightly decreases in the over-aged. The potentiodynamic polarization curves also indicate the most positive corrosion potential and the lowest corrosion current density in the peak-aged. The results of electrochemical impedance spectroscopy are in agreement with the corrosion morphologies. Furthermore, the related equivalent circuit is established to investigate the corrosion mechanism of this alloy.