Influence of carbon nanodots encapsulated polycarbazole hybrid on the corrosion inhibition performance of polyurethane nanocomposite coatings

Abstract

Herein, we present the synthesis of CD, polycarbazole (PCz), and CDs encapsulated in PCz (CD@PCz) nanofillers. These nanofillers were dispersed in a safflower oil polyurethane (PU) matrix to formulate nanocomposite coatings. The structures, morphologies, and thermal behaviors of these coatings were investigated using Fourier transform infrared (FTIR) spectroscopy, solid-state ¹³C nuclear magnetic resonance (¹³C NMR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, UV-vis diffuse reflectance spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The anticorrosive performance was evaluated using acid resistance, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and salt spray tests. The results showed that the PU nanocomposites had superior corrosion resistance performance with a very small loading amount (0.5%) of nanofiller (CD, PCz, and CD@PCz). The CD@PCz/PU nanocomposite coatings exhibited excellent corrosion resistance performance, with a low i_corr value (1.15 × 10⁻¹¹ A cm⁻²), a high E_corr value (0.05 V), and the highest protection efficiency (99.999%) compared with other coating systems. The superior anticorrosive performance of these coatings was attributed to the excellent barrier properties, strong filler–matrix interactions, and the formation of a stabilized passive layer at the coating-metal interface. These results suggested that the proposed nanocomposite coatings (CD@PCz/PU) have potential for the development of a new generation of multicomponent anticorrosive coatings with high performance.