Effective Performance of Derived Sustainable Lupine Carbon Quantum Dots as a Superior Inhibitor Material for Carbon Steel Corrosion in a Hydrochloric Acidic Environment (1.0 Molar)

Carbon and graphene-based quantum dots have recently emerged as highly valuable and widely applicable materials based on their low particle sizes (1–10 nm). The incorporated oxygen, nitrogen, and carbon functional groups can significantly enhance the binding capabilities of these materials to various surfaces. In this study, lupine seeds were employed to produce a sustainable and novel material known as lupine carbon quantum dots (LCQDs), by using a straightforward and green microwave hydrothermal reaction. The assembled LCQD material was characterized by several instrumentations such as FTIR, TEM, EDX, XRD, UV–vis, and XPS to confirm the various incorporated functionalities, morphology/particle size, elemental composition, amorphous structure, transition types, and various bonds, respectively. LCQD material was explored to investigate and assess the corrosion prevention performance by various approaches via electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and mass loss techniques. The prepared LCQDs reflected an 89.3% maximum inhibitory effectiveness for carbon steel corrosion upon using 175 mg/L LCQDs in a 1.0 M HCl environment at 40 °C. The EDX, XRD, and XPS techniques were used to confirm the effectiveness of LCQDs in protection of the carbon steel surface and discuss the corrosion inhibition mechanism. The LCQD adsorption mechanism onto carbon steel was also explored by Langmuir and Flory–Huggins isotherms, besides the kinetic–thermodynamic model, to fit the outcomes from the experimental data. The findings revealed that these models were applicable, giving ΔG^o_ads of −31 kJ/mol, while the adsorption mechanism was correlated to a physical/chemical process. Finally, the outcomes of this study refer to the potential capability of LCQD materials as sustainable corrosion inhibitors without any additional modification via doping or modification with other chemical compounds or materials.