Study the existing form of copper (p-type oxide/segregation) and its release mechanism from the passive film of Ti-7Cu alloy

•Ti-xCu alloys have n-type point defective TiO2-x barrier layer.•Copper does not form any p-type (cuprous or cupric) oxide.•Cu preferentially oxidizes at the m/f interface and dissolves at the f/s interface. The existing form of copper and its release mechanism from the passive film of Ti-7Cu alloy was studied by Quantitative analysis of depth profile and series of electrochemical tests. Results were interpreted within the Point Defect Model-II. Copper does not form any p-type (cuprous or cupric) oxide but preferentially oxidises at the metal/film interface and segregated as Cu interstitials Cui+ and become substituted as CuTix' in the oxygen-deficient TiO2-x barrier layer having n-type semiconducting character. Eventually, the segregated species of Cu preferentially dissolute through the film as Cu ions into the solution at film/solution interface via the Esaki-tunnelling effect.