Ocimum sanctum (Tulasi) as Corrosion Inhibitor on Mild Steel in Hydrochloric Acid

The aqueous extract of Ocimum sanctum as corrosion inhibitor on mild steel in 1 N hydrochloric acid was studied using the weight loss method, gasometric, potentiodynamic polarization and impedance method. The maximum inhibition efficiency was 99.6 % in the optimum concentration of the extract 6 % in v/v. Similarly, in gasometric method, maximum efficiency was 98.6% in the same concentration. It was confirmed by potentiodynamic polarization and impedance methods, which showed a maximum efficiency of 99.7% and 97.9% respectively in the same concentration. The effect of immersion time from 3 hrs to 24 hrs at 30°C on corrosion inhibition of mild steel in 1N HCl in the presence of the optimum concentration of the inhibitor (6 % in v/v) revealed that the extract of Ocimum sanctum has maximum efficiency of 99.6% in 3 hours immersion time. Potentiodynamic polarization studies indicated that the plant extract behaves as mixed type inhibitor. The results show that 6% in v/v aqueous extract of the leaves of Ocimum sanctum could serve as an effective inhibitor on the corrosion of mild steel in 1 N hydrochloric acid medium.