Carbon dots (CDs) have been studied as eco-friendly corrosion inhibitors for metals. However, the mechanisms behind their effectiveness are not fully understood. We developed a cost-effective and environmentally friendly method to synthesize Ce-doped CDs (CeCDs) using urea, ammonium citrate, and cerium nitrate. By optimizing the Ce doping concentration to 200 μg/L, we achieved a high corrosion inhibition efficiency. When tested in 1 M HCl, CeCDs at 200 mg/L showed 80 % inhibition, while ionic liquid-modified CeCDs (IL-CeCDs) demonstrated an even higher efficiency of 95.35 % on N80 steel. Both CeCDs and IL-CeCDs adsorb onto metal surfaces through a combination of physical and chemical interactions, inhibiting corrosion mainly by affecting cathodic reactions. Among different Ce-doped CDs, CeCD3N, which has a single Ce atom doping, exhibited the highest molecular reactivity, allowing it to interact more effectively with the Fe surface. Further analysis revealed that Ce doping reduces the energy gap of CDs, enhancing their reactivity. Molecular dynamics simulations showed that CeCD3N adsorbs more strongly and forms a closer inhibitor film on the Fe surface compared to other Ce-doped CDs, making it an effective corrosion inhibitor.
In this work, nitrogen-doped carbon dots (NCDs) were obtained by hydrothermal method with citric acid and ethylenediamine as precursors. The corrosion inhibition performance and mechanism of prepared the NCDs on the Q235 carbon steel in 1 M HCl solution were evaluated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curve, and surface analysis. The results that the NCDs exhibited 93% of inhibition efficiency at 100 mg/L. Electrochemical measurements demonstrated that the NCDs adsorbed on the metal surface and effectively inhibited the electron transfer process. The potentiodynamic polarization suggested that NCDs were excellent mix-type corrosion inhibition. Furthermore, NCDs successfully prevented the dissolution of anode metal and the evolution of cathode hydrogen ions. The adsorption of the NCDs followed Langmuir adsorption isotherm indicated physical and chemical adsorption. At the same time, the adsorption mechanism was analyzed, guiding the use of carbon dots as environment-friendly corrosion inhibitors in the future.
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