The Use of Novel Biosynthesized Ag-Cu-Al Nanoparticles as Corrosion Inhibitor on Mild Steel in 1 M HCl Medium

Recently, concerns have arisen over the use of most organic and inorganic substances as corrosion inhibitors due to their expensive and toxic nature. This has necessitated the search for alternative cheap and eco-friendly inhibitors. Nanoparticles, especially trimetallic nanoparticles has of recent found unique applications in various field especially in corrosion studies owing to its superior synergistic properties compared to its monometallic and bimetallic counterparts. This study addresses the need for eco-friendly inhibitors by biosynthesizing novel Ag-Cu-Al trimetallic nanoparticles using aqueous leaves extract of Hierochloe odorata. UV-Vis analysis revealed a peak maximum of 405 nm, FTIR characterization identified the possible biomolecules responsible for biosynthesis of the nanoparticles, XRD revealed an average crystalline particle size of 36 nm while SEM-EDS analysis revealed the cylindrical nature of the nanoparticles. The effect of Ag-Cu-Al nanoparticles on corrosion of mild steel in 1 M HCl was investigated by weight loss method. The corrosion rate of the steel sample was observed to decrease with increase in concentration of the nanoparticles and increased with increasing temperature, while the inhibition efficiency increased with increasing inhibitor concentration and decreased with increasing immersion time and temperature. The highest inhibition efficiency under optimum conditions was found to be 95 %. Kinetic data revealed a first order kinetic reaction while thermodynamic investigations showed that Ag-Cu-Al NPs were spontaneously adsorbed onto the mild steel surface by mixed adsorption (physical and chemical adsorption); the Langmuir adsorption isotherm model was found to have the best linear relationship. The process was endothermic as confirmed by the positive values of ΔH. SEM analysis of mild steel samples revealed the presence of adsorbed deposits of Ag-Cu-Al NPs which indicates the adsorption of the inhibitor onto the mild steel surface confirming its effectiveness in protecting the mild steel surface used in petroleum industries.