A high-resolution characterisation of localised corrosion of AA5083-H111 in simulated seawater by TEM

The localised corrosion of aluminium alloy (AA) 5083-H111 in 3.5 wt-% NaCl solution was studied by combing scanning electron microscope (SEM), focused ion beam (FIB) and transmission electron microscopy (TEM) techniques. It was found that the Ti-rich intermetallic particles (IMPs) served as the cathodes and triggered the dissolution of its adjacent Al matrix; as a result, a trench was formed between the IMP and its surrounding Al matrix. Raised 'circles' were identified on the alloy surface at the periphery of the IMPs, which was considered to be the cathodic region on which corrosion products deposited. A sub-surface that consisted of fine Al grains and corroded Al-Mg phases were observed under the raised 'circle' region.