Optimization studies of expired mouthwash drugs on the corrosion of aluminum 7475 in 1 M hydrochloric acid: Gravimetrical, electrochemical, morphological and theoretical investigations

The aim of the present work is to study the corrosion inhibition of Al 7475 alloy by an expired mouthwash drug (EMWD) in a 1 M HCl solution. The corrosion rate was optimized by the Doehlert experimental design at various temperatures, concentrations of inhibitor, and rotational velocity. The corrosion behavior was investigated by mass loss, Tafel potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. SEM, MOMT, XRD, FT-IR spectrum, and drop wettability measurement were used in characterizations of EMWD and surface morphology. Optimum conditions for corrosion control of EMWD on aluminum were 44.12 °C, 141.71 mL/L of EMWD per liter of acid, and 234.89 rpm. Maximum corrosion inhibition efficiency was 84.717% at higher levels of temperature and inhibitor concentration. It is observed that EMWD follows the Langmuir Adsorption Isotherm with negative values of ΔGadso, proposing a stable spontaneous inhibition process. The inhibitor efficiency increased as the inhibitor concentration increased. Moreover, increasing the solution temperature and rotational velocity had an adverse influence on inhibitor efficiency. The results of mass loss were in good agreement with potentiodynamic polarization and EIS. Polarization diagrams revealed that the inhibitor acts as a mixed-type inhibitor. It could be concluded that response surface Doehlert design (RSDD) was adequately applicable in the optimization of corrosion inhibition process variables and that EMWD sufficiently inhibited the corrosion of the aluminum at the studied conditions. Simulation of the EMWD molecules adsorption on the metal surface by quantum chemical theoretical studies was a powerful tool for supporting experimental outcomes.