Using ultrasound to increase copper and nickel dissolution and prevent passivation using concentrated ionic fluid.

This paper uses targeted ultrasound on a surface undergoing anodic dissolution. The aim of these experiments was to etch metals that would normally passivate. The study was carried out in deep eutectic solvents (DESs) as these are technologically useful for metal processing but suffer the disadvantages of being viscous and hence have slow mass transport which results in metal passivation. Linear sweep voltammetry showed a linear current-voltage response at potentials anodic (more positive) of the oxidation potential under sonication. Passivation was observed in silent conditions. It was also shown that the dissolution current was roughly 14 times larger under sonication. High speed imaging showed asymmetric bubble collapse leading to enhanced removal of material from the surface with etch rates as high as 3.8 μm.min–1 under ultrasonic conditions.