The reactivity of titanium has been studied in a chlorine containing environment with and without plasma. It has been found that chlorine (atoms or molecules) is not able to remove the native surface oxide unless drastic conditions are realized. Once the oxide is removed, titanium does not appreciably react with molecular chlorine without plasma unless fluorine is present on its surface. Fluorine has a catalytic effect and makes the titanium surface more reactive towards chlorine. Plasma superimposition does not change the reaction pattern, it acts only by increasing the substrate temperature and supplying energy by means of low energy ion bombardment.