[en] Zirconium in nitric solutions exhibits an excellent corrosion resistance in the passive state, and a mediocre corrosion resistance in the unpassive state with risk of stress corrosion cracking. Results of the influence of some parameters (medium, potential, temperature, stress, friction, metallurgical structure and surface state) on zirconium passivation are presented. Zirconium remains passive in a large range of HNO₃ concentration (at least up to 14.4N), in the presence of oxidizing ions (Cr⁴, Ce⁴), in a spent fuel dissolution solution. Zirconium is depassived by friction at high speed and pressure, by platinum coupling in boiling 14.4N HNO₃ with or without stress, or by imposed deformation speed under high potential. (A.B.). 8 figs., 2 tabs