This paper explores tantalum and tantalum nitride thin films produced by filtered cathodic vacuum arc deposition method as bio-stable surface treatment for Ti6Al4V titanium alloy. Effect of nitrogen to argon gas ratio on microstructure of the deposited film has been investigated. Corrosion behaviour of the films in simulated biological fluid solution was evaluated by electrochemical impedance spectroscopy. It was found that both the Ta and Ta-N films enhanced corrosion resistance of the Ti6Al4V substrate with the best protective characteristics achieved by the Ta-N film deposited at 0.25 N 2 /Ar gas ratio. The protective characteristic was attributed to the formation of tantalum oxide and oxynitride compound at the surface, as verified by X-ray photoelectron spectroscopy. Increasing N 2 /Ar gas ratio increased susceptibility to localized corrosion. The corrosion resistance decreased as the thickness of the film increased to 1 μm.