Abstract Parallel energy loss spectroscopy (PEELS), convergent beam microdiffraction and secondary ion mass spectrometry (SIMS) have revealed that extensive hydride formation can occur in Zr and Ti6A14V as a direct consequence of low energy (a few keV) Ar ion bombardment in a typical ion thinning unit. Pure hydride films several microns thick could be formed on bulk samples in a few hours of sputtering under conditions which are frequently used to prepare samples for transmission electron microscopy. This effect was largely independent of the presence of contaminating hydrogen introduced in the form of water vapour in the sputter chamber, or hydrogen contamination in the incident Ar beam. However, hydride formation could be strongly influenced by controlling the presence of hydrocarbons arising from the evaporation of pump oil. Details of the degree of hydride formation as a result of experimental conditions are presented.