Corrosion Inhibition effect of Clerodendron Colebrookianum Walp Leaves (Phuinam) Extract on the Acid Corrosion of Mild Steel

The adsorption and anticorrosion effect of crude methanolic extract of Clerodendron colebrookianum walp leaves (CCWL) were investigated towards the corrosion of mild steel in 1 N HCl using gravimetric, potentiodynamic polarization, electrochemical impedance spectroscopy and Scanning Electron Microscope techniques. The results show that CCWL is a good inhibitor and the inhibition efficiency increases inhibitor concentration to attain a maximum inhibition efficiency of 95.2% at 0.4 g L –1 (30°C). The CCWL extract was analysed by FTIR spectroscopy and GC-MS and these analysed results show the presence of possible binding sites in its. The adsorption of inhibitor on the mild steel specimen (MSS) surface is spontaneous and obeyed the Langmuir’s adsorption isotherm. The standard free energy of adsorption (–26.74 kJ mol –1 at 30°C) shows that the inhibitor is physically adsorbed on the MSS. Temperature effect on the inhibition efficiency was also studied to determine the apparent activation energy ( E a ). This results suggest that the formation of protecting layer over MSS. SEM results confirm that the evenly distribution of inhibitor film over the MSS surface.