Pectin-derived nitrogen-doped carbon dots as green corrosion inhibitors for N80 steel in 1 M sulfuric acid solution

In this study, nitrogen-doped carbon dots (N-CDs) were synthesized via a one-step hydrothermal method using pectin polysaccharide as the carbon source, with 1-hexylamine, 1,2-diaminocyclohexane, and diethylenetriamine as individual nitrogen sources. The chemical composition, fluorescence properties, and morphology of the synthesized N-CDs were characterized. Their corrosion inhibition performance on N80 steel in 1 M H 2 SO 4 was evaluated using electrochemical analyses and weight loss experiments. Tafel and EIS analyses demonstrated that at a concentration of 200 mg/L, the maximum inhibition efficiencies of PHA-CDs, PCA-CDs, and PDA-CDs, synthesized using monoamine, diamine, and triamine as nitrogen sources, were 75.3 %, 90.1 %, and 95.4 %, respectively. The inhibition efficiency increased with the total nitrogen and pyrrolic N content in the N-CDs, corresponding to the choice of nitrogen source. Weight loss experiments further confirmed these trends. Additionally, the N-CDs were found to act as mixed-type inhibitors with a predominant anodic inhibition effect and are classified as predominantly chemisorptive. The adsorption behavior adhered to the Langmuir adsorption model, where coordination complexes formed between pyrrolic N and metal Fe increase the surface coverage of the adsorption film, thereby enhancing corrosion resistance.