The technical objectives of this program are: (1) to develop a set of physics-based modeling tools to predict the initiation of hot corrosion and to address pit and fatigue crack formation in Ni-based alloys subjected to corrosive environments, (2) to implement this set of physics-based modeling tools into the DARWIN probabilistic life-prediction code, and (3) to demonstrate corrosion fatigue crack initiation and growth life prediction for turbine disks subjected to low-cycle and high-cycle fatigue loading in extreme environments. This technology will significantly improve the current ability to simulate and avoid corrosion fatigue failure of engine disks or metallic structural components due to prolonged exposure to extreme environments at elevated temperatures. Completion of the proposed program will provide probabilistic corrosion fatigue crack growth life assessment software tools for structural components subjected to aggressive hot corrosion environments. Such a suite of software tools is unique and is urgently needed for designing and improving the performance of critical structures used in the space structure and propulsion systems in commercial and military gas turbine engines, and oil and gas industries. This generic technology can also be used to provide guidance for developing new alloys or improving current Ni-based alloy designs for hot-section applications.