Neem Leaf Extract as a Corrosion Inhibitor on Mild Steel in Acidic Solution

The influence of neem leaf extract on corrosion inhibition of mild steel in 0.1 M HCl solution was studied using the weight loss method. Phytochemical test, FTIR, and GCMS analyses of neem leaf extract revealed carbonyl groups, double bond, and aromatic rings functional group makes it to be a viable plant extract that can serve as an inhibitor. The various surface weight losses on mild steel at each inhibitor concentrations were determined. 93.24% was the maximum inhibition efficiency obtained using the neem leaf extract as corrosion inhibitor. The mechanism of inhibitor adsorption on the metal steel surface was studied using Temkin, Freundlich, Langmuir adsorption isotherms. Negative value of Gibb's free energy gotten (-18.421kJ/ mol, -12.340kJ/ mol, and -9.555kJ/mol) for Langmuir, Temkin, and Freundlich isotherms respectively showed that the mild steel surface inhibition by the inhibitor is spontaneous. Mixed type of adsorption mechanisms (physisorption and chemisorption) was proposed for the neem leaf extract adsorption on the surface of mild steel. Mild steel surface was protected from corrosion due to the adherence of the phytochemical components on the mild steel surface. As the inhibitor concentrations increases with time of exposure the corrosion rate of mild steel decreases from 0.001 to 0.0002MPY.