Electropolishing of Aluminum at Room Temperature Using a Green DES of Choline Chloride and Propylene Glycol

For applications of aluminum where the smoothness or reflectivity of the aluminum matters, electropolishing is necessary to polish the aluminum surface sufficiently. This electropolishing is traditionally done with hazardous solutions in non-ideal conditions, such as low-temperature perchloric acid-ethanol mixtures. Here, we describe electropolishing of aluminum using a deep eutectic system composed of propylene glycol and choline chloride, with polishing accomplished at room temperature and using an inexpensive apparatus. This polishing was performed using both 99.5 and 99.99% pure aluminum, and scanning electron microscopy images show substantial improvement with both purities of aluminum. In addition, reflectivity measurements show significant improvement over sanding of aluminum. This method provides a simple, green method for electropolishing aluminum that can be used in any research where careful polishing of aluminum is necessary.