Regarding the use of Ni or stainless steel tubing for fluorination lines.
We have been moving nanomole quantities of molecular O2 through a vacuum
line with isotopic fidelity (i.e., no fractionation at the 0.1 to 0.2 per
mil level) for almost two years. The tubing is 316L stainless steel with
electropolished interior. Our original system included Ni components. Ni,
however, reacts readily with O2 and we were able to identify several of
these components as being sites of isotope fractionation. Indeed in one
case Ni was visibly tarnished with oxide. Ni-O2 reactions are accelerated
appreciably at temperatures as low as 35 to 40 C and will proceed even in
the presence of BrF5. Ni has superior resistance to fluorination, but the
cost is enhanced susceptibility to O2 attack.

-Ed Young
 Earth Sciences
 University of Oxford