Electropolishing of aluminium in a deep eutectic solvent

Abstract

The electropolishing of aluminium in Ethaline, a eutectic mixture of choline chloride and ethylene glycol, is investigated in this work. Electrochemical polishing is performed at electrode potentials of 1, 1.5, 2, 4 and 6 V vs. Ag pseudo-reference electrode at the temperature of 20 °C. The current efficiency of aluminium dissolution is ca. 100%. The dissolution rate grows with increasing electrode potential and is about 1–4 nm s−1. No anodization of aluminium was observed. The electropolishing of aluminium yields leveling of surface morphology and disappearance of surface defects. An increase in the electrode potential at which anodic treatment was performed results in a decrease in roughness coefficient and improvement of surface appearance (the surface becomes much brighter). The leveling of the surface profile causes an increase in microhardness, corrosion resistance and surface hydrophobicity of aluminium. Thus, deep eutectic solvent can be considered as a promising medium to perform electropolishing of aluminium.