Carbon Quantum Dots Derived from Garlic (Allium sativum) Peel as Corrosion Inhibitor for Mild Steel in HCl Solution

In this study, carbon quantum dots (CQDs) were successfully synthesized from garlic peel, with size dimensions confirmed by TEM and DLS analyses and photochemical properties validated by UV-vis and fluorescence spectroscopy. FTIR revealed chemical similarities with the precursor, while XPS revealed the presence of nitrogen and sulfur, indicating endogenous doping. The anticorrosive performance of the CQDs was demonstrated through gravimetric, electrochemical impedance, potentiodynamic polarization, and surface analyses including scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. The CQDs exhibited high inhibition efficiencies with sustained performance over time, achieving maximum inhibition efficiencies of 79% for 2 h and 96% for 24 h, as determined by gravimetric studies. This inhibition was primarily mediated through physical interactions, as indicated by temperature-dependent studies. Electrochemical measurements further confirm that the CQDs act as mixed-type inhibitors, exhibiting a predominant anodic effect. Surface analyses confirmed the formation of a protective and hydrophobic film on the steel surface. XPS, DLS, and zeta potential studies, along with Arrhenius equation analysis, demonstrated that the film forms through physical and chemical interactions between mild steel and quantum dot aggregates. These findings highlight the potential of using agro-industrial waste, such as garlic peel, as a sustainable precursor for the synthesis of effective corrosion inhibitors.