This thesis concerns the research and development of materials more resistant in extreme conditions at high temperature. It is more specifically dedicated to the development of a new concept of nuclear fuel cladding : Cr coated Zr-based claddings. The purpose of this work is to adpat the Ekinox-Zr code, initially developped for the description of diffusion phenomena in uncoated Zr claddings, to Cr-coated Zr-based claddings and create a new code : “Ekinox-Zr-Cr”. This work will be divided into two parts : a modelling/simulation one and an experimental one dedicated to the determination of the diffusion coefficients of Cr, Zr and O species inside the different phases of the system. These data constitute essential parameters for the modelisation. High temperature oxidation experiments on Cr-coated claddings will also be used in order to improve our knowledge on the different mechanisms involved and compare them to the results obtained with the Ekinox-Zr-Cr code created during this study.