Influence of nitric acid pre-treatment on Al–Cu alloys

The enrichment of copper alloying additions near the surface of sputtering-deposited Al–1.3 at.%Cu, Al–2.7 at.%Cu and Al–30 at.%Cu alloys is investigated following immersion in nitric acid, which is used commercially as a de-smutting pre-treatment. Corrosion of the alloys is revealed at rates in the range 4–13 nm min−1, leading to enrichment of copper in the alloy surface regions. Enrichments are also generated by nitric acid treatment of AA2024-T3 and AA7075-T6 alloys, with levels similar to those achieved by etching in sodium hydroxide solution. Conventional durations of de-smutting treatments in nitric acid have minor influences on the magnitude of enrichment.