The inhibition efficiency [IE] of an aqueous extract of the (Curcuma longa L.) plant material rhizome powder has been used as a corrosion inhibitor in controlling corrosion of carbon steel in sea water by the weight-loss study, in the absence and presence of Zn2+ . The main constituent of this plant extract is curcumin. The results show that 93% IE is provided by binary system consisting of 10 mL of curcumin dye (CD) and 50 ppm of Zn2+. Polarization study reveals that CD and Zn2+ system functions as mixed type inhibitor. The nature of the metal surface has been analysed by FTIR spectra and SEM analysis