The localised corrosion associated with individual second phase particles in AA7075-T6: A study by SEM, EDX, AES, SKPFM and FIB-SEM

To investigate the role of intermetallic particles in the localised corrosion of AA7075-T6, three particles were monitored over 16h immersion in 3.5wt% KCl solution. These were examined using Auger electron spectroscopy, energy dispersive X-ray spectroscopy, scanning Kelvin probe force microscopy and focused ion beam-scanning electron microscopy. Despite similar Volta potential measurements, the corrosion microchemistry varied significantly with composition. A Al7Cu2Fe intermetallic resulted in trenching while a (Al,Cu)(6)(Fe,Cu) intermetallic showed crevice corrosion and sub-surface intergranular corrosion and a Al12Fe3Si intermetallic appeared to be galvanically inactive but showed crevice formation at the matrix interface and sub-surface intergranular corrosion.