Aluminum and sulfur impurities in electropolishing baths

This study highlights the impurities formation in electropolishing bath (mixture of sulfuric and hydrofluoric acids) when aluminum is chosen as cathode material. Such impurities could partially explain the performance disparities observed on electropolished niobium RF cavities. These products might be aluminum derivatives, sulfur S and hydrogen sulfide H2S. Furthermore, parameters such as temperature, acid concentrations are also taken into account with or without applied voltage.