Imidazolium-derived ionic liquid as a steel corrosion inhibitor in acidic media: a synergistic study of experiments and DFT calculations.

The corrosion-inhibiting properties of the ionic liquid 3-benzyl-1-propyl-imidazolium bromide (RD) for carbon steel were investigated in molar hydrochloric acid. The mass-loss technique was applied to assess the inhibitory properties of the RD and demonstrated significant inhibitory activity, reaching 93.2% at 2 × 10-3 M. Kinetic and thermodynamic studies demonstrated the adsorptive character of the inhibitory process with a high activation energy (E a = 110.69 kJ mol-1) and a large adsorption equilibrium constant (K ads = 19 830 L mol-1). RD was proven to be physically adsorbed onto the surface of the carbon steel (ΔG ads = -35.04 kJ mol-1). The electrochemical analyses demonstrated a mixed-type behavior of RD molecules. This process increases the resistance to charge transfer while reducing the double-layer capacitance at the metal-solution interface. SEM images confirmed the formation and growth of a protective adsorbed layer that achieved a significant level of coverage at the ideal concentration. When inhibitors were effectively absorbed onto the carbon steel's surface, they formed a protective coating. This coating led to a smoother finish on the inhibitor-treated carbon steel, reducing its surface roughness. Additionally, in quantum chemistry, density-functional theory calculations showed excellent agreement with the experimental findings.