Electron microscopy study of the impact of solution treatment on the corrosion behavior of an Al-Zn-Mg-Cu alloy

An Al-Zn-Mg-Cu alloy treated at 475 degrees C for 1 h was found to have improved corrosion resistance compared to non-solution-treated ones. Corrosion preferentially occurred in the matrix adjacent to second phases. Nonsolution-treated samples showed varying passive film thickness and uneven solute segregation along the metal/film interface, resulting in sites susceptible to localized corrosion. Solution treatment minimized second phases, promoted uniform passive film thickness and uniform solute segregation, generating a high density of nanoscale pits during early corrosion. Our results demonstrated the metal/film interface's crucial role in alloy corrosion, offering insights for improving corrosion resistance via heat treatments and interface engineering.