In situ X-ray tomography of intergranular corrosion of 2024 and 7050 aluminium alloys

In situ synchrotron X-ray tomography was used to monitor the development of corrosion in service-like conditions. Deliquescence of sodium chloride contaminants formed a droplet environment that caused intergranular corrosion in 2024-T351 and 7050-T7451 alloys. For the 2024 alloy, corrosion grew at comparable rates in the longitudinal and long-transverse directions. Initiation occurred at an intermetallic particle, which was surrounded by a cluster of four other particles within a 20 μm radius. For the 7050 alloy, corrosion grew fastest in the long-transverse direction, intermediate in the longitudinal direction, and slowest in the short-transverse direction. Corrosion growth of one fissure was constrained due to corrosion growth in another fissure, which may indicate that the two fissures were competing for current in the cathodically limited conditions.