Effect of surface preparation treatments on copper enrichment on 2024 aluminium alloy surface

[Display omitted] •No significant evolution of the oxide thickness induced by acid pre-treatment.•Important Cu enrichment at the oxide/metal interface after acid pretretment.•The highest Cu enrichment in H2SO4: Cu0 at interface & Cu oxide in the oxide layer.•IMPs: total dealloying in HNO3/H2SO4 & partial removal in HNO3 bath.•Formation of Cu-rich remnant & possible Cu redeposition after H2SO4 treatment. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to analyse the surface modifications of AA-2024-T3 induced by model pre-treatment baths such as H2SO4, HNO3, and in a mixture of both acids. These acids are commonly used for pickling treatment, applied before conversion coating deposition. ToF-SIMS and XPS measurements showed a significant copper enrichment in metallic and oxidised states, localised at the oxide/metal interface. The sulphuric acid treatment led to the highest Cu enrichment. A lower dissolution rate of AA-2024 was observed by inductively coupled plasma optical emission spectroscopy (ICP-OES). It was concluded that the surface enrichment in Cu is mainly associated with dealloying of intermetallic particles by selective dissolution of the less noble elements.