Imidazolium-based Ionic Liquid as Efficient Corrosion Inhibitor for AA 6061 Alloy in HCl Solution

The corrosion inhibition performance of an imidazolium-based ionic liquid (IL), 1-butyl-3-methylimidazolium thiocyanate (BMIm), was studied on AA 6061 alloy in 1 M HCl solution at 303 K, 333 K, and 363 K by gravimetric tests, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) analysis. Scanning electron microscopy with energy dispersive X-ray (SEM-EDX) and X-ray photoelectron spectroscopy (XPS) were used to detect the surface morphologies and chemical composition of the surface films. The results indicate that this IL inhibits AA 6061 corrosion in acid with maximum inhibition efficiencies of 98.2%, 86.6%, and 41.2% obtained at 303 K, 333 K, and 363 K respectively. Inhibition efficiency generally decreased with increasing immersion time; the major exception was at 303 K, whereby the inhibition efficiency was detected to increase with immersion time from 30 to 90 min and then decrease slightly beyond 90 min. The results indicate that BMIm is a mixed-type inhibitor with a predominant effect on cathodic reactions. Surface morphology analyses by SEM revealed less surface damage in the presence of the inhibitor. XPS analysis established the development of a protective film on the AA 6061 surface which was hydrophobic in nature.