After coating the specimen with a thin Ti layer, the Snoek-Koster relaxation was systematically investigated without the effect of oxygen adsorption. Two relatively stable internal friction peaks were observed in cold-worked Ta-O samples, SK1 at lower temperature and SK2 at higher temperature. Their peak shape and stability with annealing and oxygen concentration were experimentally studied. The activation energy of SK1 and SK2 was measured to be 1.4 and 2.1 eV, respectively. It was suggested that SK1 corresponds to the migration of geometrical kinks on screw dislocations and SK2 corresponds to the formation and migration of kink pairs on screw dislocations. From experimental results it is estimated that the kink pair formation energy is about 0.9 eV and the binding energy of a screw dislocation with an oxygen atom is about 0.3 eV. It was additionally found that in the range of experimental error further cold-work hardly influences the Snoek peak height.