Thermodynamic and Adsorption Studies on Nyctanthes arbortristis (Night Jasmine) Leaves Extract as Corrosion Inhibitor for Mild Steel in 1N HCl Medium

The corrosion inhibition of mild steel in 1N HCl by acid extract of Nyctanthes arbortristis (night jasmine) leaves (NAL) has been studied using weight loss method. The results of the study reveal that NAL extract is a very good environment-friendly corrosion inhibitor for mild steel in acid medium with maximum inhibition efficiency of 90% at 2% v/v concentration. Inhibition efficiency of the extract is found to vary with concentration, temperature and period of immersion. Thermodynamic consideration reveals that adsorption of extract constituents on mild steel surface is spontaneous. Langmuir, Temkin, Freundlich and Flory-Huggins adsorption isotherms are obeyed. Physical adsorption mechanism is proposed for the adsorption of the inhibitor from the trend of variation of inhibition efficiency with temperature and the values of δG.