Corrosion Inhibition of Mild Steel and Aluminium in 1 M Hydrochloric Acid by Leaves Extracts of Ficus sycomorus

Inhibitory effects of Ficus sycomorus leaves extracts on the corrosion of mild steel and aluminium in 1 M hydrochloric acid (HCl) solution was studied at temperature of 30°C using gravimetric technique. Corrosion rates of mild steel and aluminium in the aggressive medium were found to increase as temperature increased, but decreased upon the addition of leaves extract of Ficus sycomorus compared to the blank. At 30°C, the inhibition efficiency increased with increase in inhibitor concentration reaching 87.84% for mild steel and 98.92% for Aluminium in the presence of 5 g/L of Ficus sycomorus leaves extracts. The results obtained show that aluminium had correlation coefficients (R2) of 0.999 and 0.876 for Langmuir and Temkin isotherms respectively while Mild steel had correlation coefficients of 0.989 and 0.751 for Langmuir and Temkin isotherms respectively. However, the inhibitor adsorption was found to fit Langmuir adsorption isotherm better than Temkin isotherm. The free energy of adsorption (∆G°ads) has negative values and this indicates that the adsorption of Ficus sycomorus on the metal surface follows a spontaneous process.