Corrosion resistance of aluminum alloy 2198 for different ageing tempers

The present work investigates the influence of two different ageing tempers (T3 and T8) on the corrosion resistance of Al-Cu-Li (2198) aluminium alloy. Electrochemical impedance spectroscopy (EIS) measurements were employed in 3.5 wt. % NaCl solution to investigate the corrosion behaviour of the alloy. Additionally, the related equivalent circuit model was established to analyse the corrosion mechanism of this alloy. The EIS results showed two different corrosion mechanisms for the different exposure times in both tempers of the alloy; pitting corrosion – associated with attack of the surface oxide film - occurs between 1 h and 6 h of immersion while corrosion dissolution becomes severe after 12 h corrosion exposure time. The T8 temper showed lower corrosion resistance of the oxide film in the first stages of exposure, but corrosion attack seems to propagate in lower rates at this temper, when compared to the T3 temper.