ELECTROPOLISHING OF NIOBIUM SRF CAVITIES IN LOW VISCOSITY AQUEOUS ELECTROLYTES WITHOUT HYDROFLUORIC ACID

Electropolishing of niobium materials and cavities is conventionally conducted in high viscosity electrolytes consisting of concentrated sulfuric and hydrofluoric acids. The use of these dangerous and ecologically damaging chemicals requires careful attention to safety protocol to avoid harmful worker exposure and environmental damage. We present an approach based on pulse reverse waveforms enabling the use of low viscosity water based electrolytes without hydrofluoric acid for electropolishing of niobium materials. The subtleties of the bipolar electropolishing process vis-a-vis conventional electropolishing are presented.