Electrochemical Investigation of Coconut Oil as Green Corrosion Inhibitor for ST37 Carbon Steel Protection

The corrosion inhibition of ST37 Carbon Steel in 1.0 M HCl by aquatic extract of coconut has been studied as a possible source of green inhibitor using the potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The aquatic extract of coconut have many advantages over classical techniques of sample preparation of plant gums (such as drying and solvent reflux).Polarization measurements showed that the extracts act as mixed typed inhibitor but under cathodic control. The passivation layer formed on metal surface, and then inhibits the anodic dissolution of steel. The compounds that available in coconut oil provides a good protection to steel against corrosion by shifting the potential at the noble direction. The Nyquist plots showed that on increasing CW concentration, increases charge transfer resistance and decreases double layer capacitance. The Results obtained from Tafel extrapolation and EIS techniques were in good agreement. SEM studies also help to understand the changes that take place on the surfacelayer with respect to change in CW concentration.