Corrosion of aluminium alloy AA2024-Τ3 specimens subjected to different artificial ageing heat treatments

The effect of artificial-ageing on corrosion behaviour of aluminium alloy (AA)2024-T3 was investigated. The natural ageing which takes place during the aircraft's lifespan was simulated with isothermal heat-treatments at 190 °C. Electrochemical impedance spectroscopy measurements were performed in different heat-treated specimens to examine the prevailing corrosion mechanisms. Additionally, pre-corroded tensile specimens from different heat-treatment conditions were mechanically tested to assess the corrosion-induced degradation. Different forms of corrosion were revealed in the investigated ageing tempers; intense localized attack was noticed in the initial (T3) and under-aged (UA) tempers. UA condition exhibited the highest susceptibility to corrosion propagation followed by T3, according to the charge transfer resistance R_CT and degradation rate of tensile elongation at fracture A_f ( ≈ 0.118) and ( ≈ 0.103), respectively. Corrosion-induced degradation rates for the peak-aged (PA) and over-aged (OA) tempers ( ≈ 0.042 and 0.054, respectively) were almost one third of UA, attributed to volume fraction and size of the precipitated second-phase particles.