  We present a detailed study based on infrared photometry of all Galactic RV
Tauri stars from the General Catalogue of Variable Stars (GCVS). RV Tauri stars
are the brightest among the population II Cepheids. They are thought to evolve
away from the asymptotic giant branch (AGB) towards the white dwarf domain.
IRAS detected several RV Tauri stars because of their large IR excesses and it
was found that they occupy a specific region in the [12] - [25], [25] - [60]
IRAS two-colour diagram. We used the all sky survey of WISE to extend these
studies and compare the infrared properties of all RV Tauri stars in the GCVS
with a selected sample of post-AGB objects with the goal to place the RV Tauri
pulsators in the context of post-AGB evolution. Moreover, we correlated the IR
properties of both the RV Tauri stars and the comparison sample with other
observables like binarity and the presence of a photospheric chemical anomaly
called depletion. We find that Galactic RV Tauri stars display a range of
infrared properties and we differentiate between disc sources, objects with no
IR excess and objects for which the spectral energy distribution (SED) is
uncertain. We obtain a clear correlation between disc sources and binarity. RV
Tauri stars with a variable mean magnitude are exclusively found among the disc
sources. We also find evidence for disc evolution among the binaries.
Furthermore our studies show that the presence of a disc seems to be a
necessary but not sufficient condition for the depletion process to become
efficient.
