Add to ORKGInternational audienceZircaloy4 (Zy-4) cladding, providing the first containment barrier of UO2 fuel in pressurized water reactor, could be exposed to air during accidental conditions. Using thermogravimetry a kinetic analysis of Zy-4 corrosion was made at 850°C in nitrogen and oxygen mixtures during post-transition stage. During experiments, jumps in oxygen partial pressure and in nitrogen partial pressure have been performed. The kinetic rate was found to depend on oxygen partial pressure whereas nitrogen partial pressure had no influence. Characterization techniques helped in explaining the acceleration of the corrosion rate and to propose a kinetic law based on nucleation and growth processes