In this study, effect of corrosion on injected fuel quantity and spray geometry has been investigated experimentally in a piezo-driven common rail diesel injector. We performed the following examination steps on the nozzle parts for the cases prior to corrosion, after corrosion and after cleaning the corrosion material: (i) all important regions of the nozzle parts were photographed, (ii) microscopic pictures of the nozzle tip and interior of holes from outside have been taken with Scanning Electron Microscope, (iii) injection jets were photographed, (iv) injection quantities for different injection pressures and duration were determined and lastly, (v) hydraulic measurement of the nozzle was performed. Hydraulic measurement of the nozzle (in cm(3)/30 s@ 100 bar) showed that injection quantity decreased 26.26% after corrosion because of the corrosion deposits blocking nozzle hole and increased 5.68% after cleaning of deposits due to the enlargement of the holes. (C) 2011 Elsevier Ltd. All rights reserved.