FIB/SEM study of AA2024 corrosion under a seawater drop: Part I

The role of metallic microstructure in 0.5 μl seawater droplet corrosion of aluminium alloy 2024 (AA2024) has been investigated. Focussed ion beam/scanning electron microscopy (FIB/SEM) was used to determine the relationships between the corrosion products formed at specific sites at the surface and the underlying attack mechanisms. Dealloying of S-phase particles, matrix/particle interfacial attack and grain boundary attack were the predominant attack modes. Cooperative behaviour between IM particles was made possible by networks of etched grain boundaries, which provided a connecting path.

Research highlights
► Microstructure dictates attack site distribution on AA2024 under a seawater drop.
► S-phase dealloying was influenced by geometry and crystallography.
► Matrix dissolution adjacent to S-phase went simultaneously with S-phase dealloying.
► S-phase/matrix interfacial attack followed an acid dissolution model.
► Cooperative attack on intermetallic particles linked by grain boundary networks.