In this study, effect of friction stir processing on corrosion and erosion-corrosion behavior of nickel-aluminum bronze were evaluated. Plates of nickel-aluminum bronze were cast in sand. These plates were friction stir processed in wide range of processing parameters (rotation rates and traversing speed). the microstructure were identified using optical microscopy and the results shows that the coarse and heterogeneous structure of cast nickel-aluminum bronze were changed to homogeneous and fine grain structure under friction stir processing and different structure were produced in the stir zone and this is parameter dependence. Hardness is the most important mechanical property of the surface of material that can affect the erosion-corrosion behavior of materials. So the microhardness measurements were done before and after friction stir processing. The results show that, first the surface microhardness increase by friction stir processing and second, the increase is parameter dependence. The electrochemical corrosion behavior of friction stir processed nickel-aluminum bronze was evaluated through potentiodynamic polarization and electrochemical impedance spectroscopy tests and the results shows that resistance to electrochemical corrosion decrease by friction stir processing and corrosion rate was in friction stir processed samples was parameter dependence. The cast nickel-aluminum bronze is prone to crevice corrosion in seawater. Crevice corrosion behavior of friction stir processed nickel-aluminum bronze was evaluated by cyclic potentiodynamic polarization and the results show that resistance to crevice corrosion increased by friction stir processing. Passive film characterization was evaluated by electrochemical impedance spectroscopy and field emission scanning microscopy. The results show that resistance to corrosion of passive film increase by friction stir processing. The image of field emission scanning microscopy shows continuity of passive film of friction stir processed nickel-aluminum bronze. Annealing process increase the resistance of cast nickel-aluminum bronze to electrochemical corrosion. Friction stir processed sample annealed by similar process, the results shows the positive effect of this process on friction stir processed nickel-aluminum bronze samples, too. Erosion-corrosion tests were carried out by different impact angles on both cast and friction stir processed nickel-aluminum bronze. The weight loss results show that all of samples had ductile erosion-corrosion behavior and the rate of weight loss increased by friction stir processing. Pure erosion tests were done for all of samples again. The results of weight loss show the negative synergy effect by interaction of corrosion and erosion factors. Keyword: Nickel-Aluminum Bronze, Friction Stir Processing, Electrochemical Corrosion Behavior, Erosion-Corrosion