Inhibition of corrosion of mild steel in sea water by an aqueous extract of turmeric powder

An aqueous extract of turmeric powder (Curcuma longa) has been used as corrosion inhibitor, to control corrosion of mild steel in sea water.Methods such as weight loss method, polarization study and AC impedance spectra have been used.The protective film has been analyzed by UVvisible spectra, Fluorescence spectra and FTIR spectra.The surface morphology has been analyzed by SEM.The Hardness of a metal before and after immersion has been determined.Weight loss study reveals that the maximum corrosion inhibition efficiency of 98% is offered by 10 ml of Turmeric extract.The adsorption study reveals that the active principles (Curcumin) are adsorbed on metal surface by Langmuir absorption isotherm.Polarization study reveals that the inhibitor function as cathodic inhibitor, because the corrosion potential is shifted to more negative side.AC impedance spectra confirm the formation of a protective film on the metal surface.Fluorescence spectra confirm that the protective film consists of Fe 2+ -Curcumin complex formed on the anodic sites of the metal surface.This is confirmed by FTIR spectra.Vicker hardness (HV) study reveals that in presence of inhibitors, the hardness of the metal increases.In the absence of inhibitors (corrosive medium-sea water), the hardness of the metal decreases.These findings may be used in cooling water systems where sea water can be used as coolant.