We have observed a substantial decrease in barium sputter yield as a function of exposure time when a barium surface is bombarded with an intense flux of positive hydrogen or deuterium ions, extracted from a plasma. This effect is attributed to an increase of surface hydrogen concentration which results in enhanced preferential sputtering of hydrogen surface atoms. The sputtering process is observed by means of optical emission spectroscopy. Whenever the surface is saturated with hydrogen, the sputtered barium yield is constant in time, and scales with the sputter coefficient, which is dependent on the energy of the incident ions. The relative decrease of the sputtered barium yield is shown to scale with the incident positive ion current density as the saturation concentration depends on this current density.