Thin-film polycrystalline TiN with an approximate 2 nm thick native TiO2 overlayer is bombarded with 50 to 200 eV Ar ions in an electron cyclotron resonance plasma. In situ x-ray photoelectron spectroscopy and static secondary ion mass spectrometry suggest complete removal of oxygen from the planar surface, independent of ion energy, with TiO2 remaining on the columnar grain boundaries. The TiN etching rate increases from 6 to 14 nm/min as the ion energy is raised from 100 to 200 eV. The TiN stoichiometry does not change with ion bombardment.