The semiconducting properties of passive films formed on nickel-base alloys type Alloy 600 in berate buffer solution were studied by capacitance measurements and photoelectrochemistry. The influence of the alloying elements (Fe, Ni, Cr) on the film properties was examined using pure metals and pure alloys. The results obtained show that the presence of both chromium and mixed nickel-iron oxides in the films revealed by quantitative analysis develops a p-n heterojunction that controls their electronic structure, in a similar manner to the case of stainless steels. The nickel oxide present in the films acts as a barrier layer that confers improved protection. The relationship between the electronic structure and the physicochemical properties of the passive film are discussed.