Ionic Liquid-Involved Synthesis of Carbon Dots as Effective Corrosion Inhibitors for 45# Carbon Steel in 1 M HCl Solution

In this study, a series of Ionic liquid-derived carbon dots (IL-CDs) were synthesized by microwave method from L-histidine and imidazolium-based ILs included 1-butyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride and 1-decyl-3-methylimidazolium chloride. Their structures were elucidated using Fourier transform infrared spectroscopy (FTIR), Ultraviolet–visible spectrum (UV–vis), and nuclear magnetic resonance (NMR). The inhibition efficacy of IL-CDs on 45# steel within a 298 K, 1 M HCl solution system was investigated employing various techniques, including electrochemical analysis, weight loss measurement, scanning electron microscopy (SEM), atomic force microscopy (AFM), and molecular dynamics simulations. The microstructure and surface properties IL-CDs were obtained through a series of characterizations; and their corrosion inhibition performance for 45# steel was evaluated using weight loss and electrochemical methods in 1 M HCl solution. The electrochemical impedance spectroscopy (EIS) results showed that the corrosion inhibition efficiency of CDs in 1 M HCl solution could reach 98.2% at a concentration of 15 ppm, and 95% even at an increased temperature of 313 K. The strong adsorption of IL-CDs follows the Langmuir adsorption model, and the Gibbs free energy increases with the chain length of ionic liquids. The adsorption behavior of the IL-CDs on the carbon steel surface shows the chemisorption feature. Graphical The corrosion inhibition mechanism involves carbon dots that adsorb on the surface of carbon steel to form a hydrophobic film, which suppresses hydrogen evolution at the cathode and oxidation reactions at the anode.