Localised corrosion initiation and microstructural characterisation of an Al 2024 alloy with a higher Cu to Mg ratio

An Al 2024 (AA2024-T351) alloy having less Mg and a higher proportion of Cu to Mg (mass ratio ≈3.7) has been characterised to provide input data for microscale and macroscale corrosion models. The Al 2024 alloy microstructure has a significant presence of nanoscale dispersoid and microscale AlCuFeMnSi (2nd phase) intermetallic particles, but a smaller population of microscale S phase (Al2CuMg) and θ phase (Al2Cu) intermetallic particles. Microscale electrochemical data show that pitting potential (SCE) values for 2nd phase, S phase, or matrix overlap significantly. The localised corrosion susceptibility is affected by S and inhomogeneous 2nd phase particles.

► Al 2024 alloy with higher Cu:Mg ratio has been characterised for corrosion modelling.
► Intermetallic particles of AlCuFeMnSi dominate the Al 2024 microstructure.
► Al 2024 localised corrosion mechanism differs from that of the more common Al 2024.
► S phase and AlCuFeMnSi particles play a role in localised corrosion susceptibility.