Experimental and Theoretical Chemical Studies of Linalool and Caffeine as Corrosion Inhibitors for Mild Steel in Sulfuric Acid Solutions

Abstract

This study used potentiodynamic polarization curve measurements, electrochemical impedance spectroscopy (EIS), and quantum chemical calculations to examine the inhibitory and adsorption properties of linalool and caffeine on the corrosion of mild steel in sulfuric acid (H2 SO4) solutions. The obtained results revealed that linalool is more effective than caffeine as a corrosion inhibitor for mild steel in 0.5 M H2 SO4 solutions. Potentiodynamic polarization curves indicated that linalool acts as a mixed-type inhibitor, whereas caffeine is an anodic-type inhibitor for mild steel in 0.5 M H2 SO4 solutions. According to the impedance measurements, the corrosion mechanism occurs under activation control. Theoretical fitting was also used to assess various adsorption isotherms, including Langmuir, Flory-Huggins, and kinetic-thermodynamic models. Both inhibitors act through a physical adsorption mechanism on the mild steel surface. However, their adsorption process is a non-ideal one. Quantum chemical parameters were calculated and explained.