Abstarct: Service life of concrete structures in some environments is limited by the corrosion of rebars. In fact, the corrosion of reinforcement is the oxidation of steel and formation corrosion products such as hydrated magnetite and ferrous oxides, some of which occupy much greater volume than the original iron. These products cause internal pressure and cause cracking in concrete cover. The end of service life of concrete structures is usually considered as the cracking and spalling of concrete cover. At this stage, reinforcing steel is directly subjected to severe corrosion condition and bond strength is considerably decreased. It can be seen that the estimation of cracking time in concrete structures is very important in the design of these structures baxsed on service life. In this thesis first, a lab specimen is modeled using finite element method, in ANSYS software. After applying internal pressure, due to the formation of corrosion products, on the existing holes in the model, the required pressure to cause cracking is obtained. In this study concrete behavior was considered as multi linear isotropic hardening in compression and smeared crack in tension. The obtained results were in good agreement with the lab results and showed that in models with similar geometry and mechanical properties, the more the thickness of concrete cover, the more required pressure for cracks to appear. In the next step, baxsed on some existing models and the FE model developed in the first step of study, the required time to produce a crack was evaluated. It was found that the main effective parameters on time to cracking is the thickness of concrete cover, rebar diameter, modulus of elasticity, kind of corrosive products and corrosion intensity.