  We report on the evaluation of commercial electroless nickel phosphorus (NiP)
coatings for ultracold neutron (UCN) transport and storage. The material
potential of 50~$\mu$m thick NiP coatings on stainless steel and aluminum
substrates was measured to be $V_F = 213(5.2)$~neV using the time-of-flight
spectrometer ASTERIX at the Lujan Center. The loss per bounce probability was
measured in pinhole bottling experiments carried out at ultracold neutron
sources at Los Alamos Neutron Science Center and the Institut Laue-Langevin.
For these tests a new guide coupling design was used to minimize gaps between
the guide sections. The observed UCN loss in the bottle was interpreted in
terms of an energy independent effective loss per bounce, which is the
appropriate model when gaps in the system and upscattering are the dominate
loss mechanisms, yielding a loss per bounce of $1.3(1) \times 10^{-4}$. We also
present a detailed discussion of the pinhole bottling methodology and an energy
dependent analysis of the experimental results.
