Corrosion Inhibition of Mild Steel Using Green Synthesized Tungsten Oxide Nanoparticles in Acidic Media

Corrosion is a serious problem in industrial applications, and therefore the need to produce environmentally friendly inhibitors. The current research examines the corrosion inhibition performance of eco-synthesized tungsten oxide nanoparticles (WO₃ NPs) derived from Cassia fistula leaf extract as an inhibitor for mild steel in 1M HCl. Characterization confirmed the successful synthesis of the WO₃ NPs with a granular, closely packed nature. Weight loss measurements revealed that corrosion rates decreased significantly with an increase in the concentration of the WO₃ NPs, with an inhibition of over 85% being achieved with 200 ppm. Electrochemical measurements including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed enhanced charge storage capacity, an increase in the charge transfer resistance, and a decrease in the corrosion current density. Potentiodynamic polarization studies corroborated the positive shift in the corrosion potential and a great reduction in the current density from 1.2 × 10⁻³ A/cm² (control) to 2.8 × 10⁻⁵ A/cm² with 500 ppm of the WO₃ NPs, demonstrating the immense protective effect of the NPs. Scanning electron microscopy (SEM) revealed a uniform development of a protective layer over the steel surface that prevents the direct acid attack and decreases pitting. The inhibition performance of the WO₃ NPs was comparable to or better than the conventional inhibitors but with eco-friendliness. These findings support the use of the biosynthesized WO₃ NPs as a promising sustainable alternative to the protection of corrosion in an acid environment with potential industrial applications.