Corrosion in artificial defects. I: Development of corrosion

Artificial defects (slots) were milled through a polyurethane topcoat and chromate-inhibited epoxy polyamide primer to the underlying aluminium alloy 2024-T3. The slots were then exposed to neutral salt spray (NSS) for up to 16 days. Prior to and after exposure, the slots were examined using scanning electron microscopy with energy dispersive X-ray analysis (SEM/EDS) and Raman spectroscopy. The milling process generated features on the surface not seen on polished surfaces, including smearing of the matrix alloy and fragmentation of Cu–Fe–Mn–Al intermetallic particles. It was found that the smears and S-phase particles acted as sites for the initiation of corrosion, which eventually developed more generally across the surface.