Fundamental and sustainability of nanoengineered green corrosion inhibitors

Corrosion of industrial metals remains a critical economic and environmental challenge, with traditional inhibitors often posing toxicity and non-degradability risks. This review quantitatively examines the synergy between nanotechnology and green chemistry in developing nanoengineered green corrosion inhibitors (NGIs). Electrochemical analyses reveal that the integration of plant extracts with nanomaterials enhances inhibition efficiency significantly: non-nano plant extracts achieve efficiencies of approximately 69–96.41%, while nanoengineered systems consistently reach approximately 85–99% in aggressive media (e.g., HCl, H2SO4). For instance, green-synthesized silver nanoparticles (AgNPs) from tobacco extract provide 98% protection for carbon steel in 0.5 M HCl, while SiO2 nanoparticles from rice husk ash achieve 99% inhibition. These improvements are attributed to increased surface coverage, enhanced charge transfer resistance (e.g., from 200 to 359.3Ω·cm2 with ZnO-NPs), and reduced corrosion current densities. Nanocoatings and nanocomposites further improve barrier properties, reducing porosity and extending service life. However, challenges in scalability, nanoparticle dispersion, and long-term durability under real-world conditions remain. This review highlights the > 90% efficiency trends of NGIs, supported by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and surface characterization data, positioning them as sustainable, high-performance alternatives to conventional inhibitors.