A Review on Green Corrosion Inhibition of Mild Steel in Acidic Medium Using Azadirachta indica (Neem) Leaf Extract

Abstract:

Corrosion of mild steel in acidic environments poses a significant challenge in various industrial operations such as acid pickling, descaling, and oil well acidification. The demand for environmentally safe and cost-effective corrosion inhibitors has led to increasing interest in green inhibitors derived from natural sources. This review focuses on the effectiveness of Azadirachta indica (Neem) leaf extract as a sustainable corrosion inhibitor for mild steel in acidic media. Neem leaves contain a variety of bioactive constituents, including alkaloids, flavonoids, tannins, saponins, and terpenoids, which play a crucial role in inhibiting corrosion through adsorption on the metal surface. The inhibition efficiency of Neem leaf extract is influenced by factors such as concentration, temperature, and exposure time. Generally, higher concentrations of the extract lead to increased inhibition efficiency, while elevated temperatures may reduce its effectiveness due to desorption. The adsorption process is often described by isotherm models such as Langmuir, indicating the formation of a protective monolayer film on the metal surface. Both physisorption and chemisorption mechanisms are involved in the corrosion inhibition process. Various experimental techniques, including weight loss measurements, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization studies, have been employed to evaluate the performance of Neem extract. Surface characterization methods further confirm the formation of a protective film. Owing to its biodegradability, non-toxicity, and economic feasibility, Neem leaf extract emerges as a promising green alternative for corrosion control. This review highlights recent developments, mechanisms, and industrial relevance of Neem-based corrosion inhibitors.