Effects of Surface Functional Groups of Nanomaterials on Corrosion Inhibition Performance and Mechanisms
Surface functional groups dictate the corrosion inhibition efficiency of nanomaterials, yet isolating their single-variable effect has remained intractable because particle size and carbon core structure typically co-vary during synthesis. This study employs a post-modification strategy to prepare three carbon dot (CD) variants with nearly identical particle size and graphitization degree but distinctly different surface terminations: carboxyl-rich (OCDs), thiol-rich (SCDs), and amino-rich (NCDs). Transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy confirm that the carbon cores are structurally equivalent, while surface chemistry differs markedly. Weight loss measurements, electrochemical impedance spectroscopy, and potentiodynamic polarization consistently rank inhibition efficiency (IE) in 1 mol/L HCl at 100 mg/L as NCDs (91.2%) > SCDs (86.6%) > OCDs (79.0%). The mechanism involves dual protection: adsorption film formation and induced oxide film densification. NCDs adopt a parallel adsorption configuration with the strongest binding energy, yielding the densest protective film and promoting a compact oxide layer. SCDs also adsorb in parallel but with weaker film-forming capability. OCDs cannot achieve parallel adsorption, exhibit the lowest binding energy, and produce the least dense films. These findings establish a direct structure–property relationship for surface group engineering of nanomaterial corrosion inhibitors, providing a validated experimental framework for designing high-efficiency inhibitors. The study is limited to 25 °C; future work will address temperature effects (40, 60, 80 °C), long-term dissolution–adsorption equilibria, and in situ characterization of Fe2+/Fe3+ ratios in the oxide film.