The strongly correlated rare earth nitrides display unusual coupled magnetic, electronic and superconducting properties, with predicted topological states. However, their air-sensitiveness has prevented in-depth investigations of their properties. In this paper, we show that a 100 nm thick epitaxial samarium layer provides adequate passivation of 100 nm thick thin films of gadolinium nitride (GdN), the prototypical rare earth nitride, enabling ex-situ magnetic and structural characterizations. Using reflection high-energy electron diffraction, atomic force microscopy and energy dispersive x-ray spectroscopy, we investigate the thermal desorption of the samarium layer under vacuum. We finally demonstrate successful removal of the samarium capping layer in a separate vacuum chamber after exposure to air using a combination of argon ion sputtering and thermal desorption at 400°C, recovering the GdN surface.