             !" #$! $% && ’&($$)"  (&*  +, $& #$! ($*&)& (&-$%$&.(                      Central Department of Chemistry, Tribhuvan University, Kathmandu, Nepal. email:bhattarai_05@yahoo.com            Synergistic effect of the simultaneous additions of tungsten and tantalum in the extremely high corrosion resistance properties of the spontaneously passivated sputter–deposited W–xTa alloys was investigated using a non−destructive angle resolved X−ray photoelectron spectroscopy (angle resolved XPS) techniques in this study. In−depth surface analyses of the thin passive films formed on the spontaneously passivated amorphous/nanocrystalline W–xTA alloys using angle resolved XPS analyses revealed that the high corrosion resistance of the alloys is mostly due to the formation of homogeneous passive double oxyhydroxide films consisting of W ox and Ta 4+ cations with a small concentration gradients in–depth particularly after immersion between 20– 168 h in 12 M HCl solution open to air at 30°C. Consequently, tantalum metal acts synergistically with tungsten in enhancing the spontaneous passivity as well as the high corrosion resistance of the sputter–deposited binary W–xTa alloys in 12 M HCl solution.  Sputter deposition; W–xTa alloys; 12 M HCl; Take–off angle !" # An Angle Resolved XPS proves as one of the promising in−depth compositional analyses of thin films to investigate chemical compositions, oxidation states, chemical shifts, binding energies and electronic structures of the surface films [1−7]. For this purpose the non−destructive angle resolved XPS technique is widely used by a number of researchers to gain about the in−depth concentration profiles of the passive films. In principle, the in−depth information of the passive film depends on the effective escape depth of the ejected photoelectrons, which increases with an increase in the take−off angle of photoelectrons relative to the surface of the sample specimen [1−8]. Therefore, the surface sensitivity is varied by changing the take−off angle of photoelectrons (θ) as explain by equation (1). In general, the surface sensitivity is varied by changing the take−off angle of photoelectrons. At a lower take−off angle of photoelectrons, the intensity signals (I) from the sample species located in the exterior part of the surface films are enhanced. Therefore, the apparent compositions of the surface films are changed with the take−off angle of photoelectrons in the angle resolved XPS measurements.