he corrosion inhibition effect of expired naproxen on aluminum (Al) in a 3 M hydrochloric acid (HCl) environment was studied by gasometric, Tafel plot, impedance, quantum chemical, and scanning electron microscopy (SEM) studies. The gasometric results showed that expired naproxen behaves as a corrosion inhibitor for Al in a 3 M HCl medium. The protection efficiency was enhanced and the evolution of hydrogen gas decreased as the concentration of expired naproxen rose. The Tafel plots showed mixed corrosion inhibition properties of expired naproxen. Impedance spectroscopy showed that the expired naproxen inhibited the corrosion of Al by adhering to the surface. Quantum chemical calculations showed that the electron rich elements in the expired naproxen had an interaction capacity with the surface of Al in the 3 M HCl solution medium. SEM photographs showed the corrosion inhibition property of expired naproxen. Due to the presence of electron rich elements in the expired naproxen, the compound is considered to be a superior corrosion inhibitor.
