INFN/LNL, Legnaro, Padova
Univ. degli Studi di Padova, Padova
Among possible Surface Treatments, Electropolishing (EP) occupies a key role, because is the cleanest way for removing hundreds of microns of material. The standard recipe for Niobium EP foresees the utilization of a mixture of H2SO4 and HF. Literature results are excellent, however the EP of thousands of cavities could become an industrial nightmare from the point of view of security at work. HF is not like other highly corrosive acids: if it gets in contact with skin, pain is not felt, but F- ions begin to pass through, searching for the bone calcium. Up to little time ago, it was common opinion that Niobium EP without HF was impossible, unless of explosive mixtures based on perchloric acid. This is not true anymore! Since a few years a green chemistry based on ionic liquids has come to the fore, and our group was the first to EP Niobium by a harmless mixture of Choline Chloride and Urea heated around 150°C. If compared to the HF based recipe, ionic liquids provide higher etching rate and lower surface roughness. In this talk, the application to 6GHz cavity EP will be reported and the addition of a secret third "magic" component to Choline Chloride and Urea will also be revealed.
