In this study, the effect of corrosion on the injected fuel quantity and spray geometry was investigated experimentally in two piezo driven common rail diesel injectors. First, the corrosive environment that the injectors are exposed to inside the engine was experimentally realised. Injector parts were subjected to several applications. Then, the first and the second injector parts were kept at room temperature for 2 and 7 days respectively. Thus, the growth of corrosion rate in time was observed. Finally, different examination steps on the nozzle parts were performed for the cases before corrosion, after corrosion and after removal of the corrosion material. It was observed that the injection quantities for the first and second nozzles after corrosion decreased by 31.43 and 26.26% respectively, due to the deposits inside the injection holes. The injection quantities for two nozzles increased by 3.93 and 5.68% respectively, due to the enlargement of the holes after removal of corrosion deposits.