The Mechanism of Electropolishing of Niobium in Hydrofluoric-Sulfuric Acid Electrolyte
Niobium surfaces are commonly electropolished in an effort to obtain optimal smoothness for high-field superconducting radio-frequency cavity applications. We report the use of controlled electrochemical analysis techniques to characterize electropolishing of Nb in a sulfuric and hydrofluoric acid electrolyte. Through the use of a reference electrode, we are able to clearly distinguish the anode and cathode polarization potentials as well as the electrolyte voltage drop, which together sum to the applied power supply voltage. We then identify the temperature and HF concentration dependence of each potential. We also report the use of electrochemical impedance spectroscopy (EIS) on this system. EIS results are consistent with the compact salt film mechanism for niobium electropolishing (EP) in this electrolyte and are not consistent with either the porous salt film or the absorbate-acceptor mechanism. Microscopic understanding of the basic Nb EP mechanism is expected to provide an appro
- Research Organization:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-060R23177
- OSTI ID:
- 955977
- Report Number(s):
- JLAB-FEL-08-737; DOE/OR/23177-0452; JESOAN; TRN: US1004831
- Journal Information:
- Journal of The Electrochemical Society, Vol. 155; ISSN 0013-4651
- Country of Publication:
- United States
- Language:
- English
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