Tritium implanted into the first wall of a fusion reactor can permeate through the wall and enter the coolant. Since this loss pathway for tritium could be a significant safety concern, an experiment was performed to determine permeation during bombardment of a stainless steel sample with a deuterium ion beam. The results indicate that interaction of the ion beam with the front surface increases deuterium reemission and consequently reduces the permeation rate. The surface modification most likely responsible for this effect is sputter removal of surface oxides.