Radiation field reduction in the primary heat transport (PHT) system of water-cooled reactors can be achieved by 'dilute chemical decontamination (DCD)' process. The corrosion behaviour of carbon steel has been studied in the absence and presence of different concentrations of cinnamaldehyde in 4.76 mM L-1 of citric acid for different immersion times (6 h and 24 h) at 30 degrees C using weight loss, potentiodynamic polarization and impedance measurements. Cinnamaldehyde has given an inhibition efficiency of about 90% at 15.15 mM L-1 and inhibition efficiency is decreased to 82% when duration of immersion increased from 6 h to 24 h. Electrochemical studies follow the same trend as those observed in weight loss measurements. The formation of the adsorbed inhibitor film on the carbon steel was further confirmed by FTIR studies. (C) 2008 Elsevier B.V. All rights reserved.