Effect of artificial aging on the corrosion behaviour of a recycled B206 Al-Cu alloy in chloride solution

This study investigates the influence of T7 heat treatment on the corrosion behaviour of recycled Al–Cu (B206-type) casting alloy in 3.5 wt% NaCl solution. The primary objective is to assess whether the microstructural homogenisation induced by T7 ageing can mitigate the chloride-induced localised corrosion, even when the corrosion potential becomes more active. To this end, electrochemical measurements (open-circuit potential and potentiodynamic polarisation), static immersion tests, and microstructural characterisation using optical microscopy, scanning electron microscopy (SEM) and energy dispersive x-ray spectrometry (EDX) mapping were performed on the as-cast and T7-treated specimens. The T7 temper modifies the electrochemical response of the alloy, causing a significant reduction in the corrosion rate and a transition from predominantly cathodic control with rapid anodic activation in the as-cast state to mixed activation–diffusion control with an incipient quasi-passive region. Immersion and surface analyses reveal that the as-cast alloy is prone to severe intermetallic-assisted pitting with abundant corrosion products, whereas the T7-treated condition primarily exhibits more uniform surface attack with limited material loss. These changes are consistent with the breakup of coarse heterogeneous Cu-rich intermetallic networks into finer and more uniformly dispersed precipitates, which weakens the micro-galvanic coupling between the matrix and secondary phases. Overall, the results demonstrate that an appropriately designed T7 heat treatment can significantly enhance the corrosion resistance of recycled B206-type alloys by altering the corrosion mechanism through microstructural control, thereby supporting their use in durable lightweight components exposed to environments with chloride.