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

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 (ICPOES). 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.

Automated summary

XPS and ToF-SIMS analysis revealed that surface modifications induced by H2SO4, HNO3, and a mixture of both acids resulted in significant copper enrichment at the oxide/metal interface of AA-2024-T3. This enrichment was mainly attributed to selective dissolution of less noble elements, leading to dealloying of intermetallic particles.