Study on anticorrosive and self-healing properties of acrylic resin modified with nitrogen-doped carbon quantum dots

Acrylic resins are widely used in the marine industry due to their low cost, weathering and pollution resistance, but deficiencies in corrosion resistance and poor stability limit their applications. To overcome this challenge, nitrogen-doped carbon quantum dots (N-CQDs) with special structures (Pyridine, Pyrrole and Graphite N's) and multiple functional groups were successfully synthesized in this study using citric acid and ethylenediamine as the precursors, with the former special structure displaying a key role in catalyzing the conversion of corrosive medium (O2), and the latter being able to form a stable complex with Fe3+, which effectively retarded the corrosion occurrence. Moreover, the nitrogen, hydrogen, and oxygen atoms in the N-CQDs can form hydrogen-bonded cross-links with the acrylic resin, which not only enhances the self-healing ability of the acrylic resin, but also it significantly improves the overall stability. Electrochemical impedance spectroscopy (EIS) analysis indicated that the impedance modulus of the N-CQDs@PAZ/N-PMI composite coatings prepared after the introduction of N-CQDs into PAZ/N-PMI resins was as high as 1011 Ω∙cm2, which was four orders of magnitude higher than that of the pure PAZ/N-PMI coatings (107 Ω∙cm2). Furthermore, the coating remained effective after 59 days of immersion in 3.5 wt% NaCl solution, demonstrating its long-term corrosion protection. Further microscopic characterization results demonstrated that the N-CQDs@PAZ/N-PMI composite coatings have excellent self-healing ability compared with the pure resin coatings.