In this work, a phase field model is developed to study the fracture behavior of corrosioninduced cracking in reinforced concrete structures. The cracks induced by the expansion of corrosion products are modelled by the phase field method [1,2], which can handle initiation, branching, and complex geometrical crack configurations easily. In addition, the phase field has proved to be a convenient tool to describe crack propagation in highly heterogeneous materials such as concrete, as explicit geometrical descriptions arising e.g. from micro-tomography can be directly used [3]. In the present work, heterogeneities in concrete are either explicitly modeled for large defects, or by appropriate stochastic models. A model is proposed to describe the kinetics of corrosion product expansion, and a diffusion model is introduced to describe the effects of chloride ions on the distribution of the corrosion products. An explicit description of crack patterns on the external boundaries are obtained from 3D configurations for various configurations and evolutions of local corrosion. The simulations are used to develop an inverse approach relating external observation to the local damage state of reinforcements. The procedure is applied to various geometrical configurations of reinforcements and external chloride penetration conditions.