  Electroless nickel plating is an established industrial process that provides
a robust and relatively low-cost coating suitable for transporting and storing
ultracold neutrons (UCN). Using roughness measurements and UCN-storage
experiments we characterized UCN guides made from polished aluminum or
stainless-steel tubes plated by several vendors. All electroless nickel
platings were similarly suited for UCN storage with an average loss probability
per wall bounce of $2.8\cdot10^{-4}$ to $4.1\cdot10^{-4}$ for energies between
90 neV and 190 neV, or a ratio of imaginary to real Fermi potential $\eta$ of
$1.7\cdot10^{-4}$ to $3.3\cdot10^{-4}$. Measurements at different elevations
indicate that the energy dependence of UCN losses is well described by the
imaginary Fermi potential. Some special considerations are required to avoid an
increase in surface roughness during the plating process and hence a reduction
in UCN transmission. Increased roughness had only a minor impact on storage
properties. Based on these findings we chose a vendor to plate the
UCN-production vessel that will contain the superfluid-helium converter for the
new TRIUMF UltraCold Advanced Neutron (TUCAN) source, achieving acceptable
UCN-storage properties with ${\eta=3.5(5)\cdot10^{-4}}$.
