Halloysite@Polyaniline Nanoparticles Loaded with the Praseodymium (III) Cation for Improving Active Corrosion Protection of Waterborne Epoxy Coating

The corrosion resistance of the waterborne epoxy coating is poor during long-term service, which greatly limits its widespread application. In this paper, the halloysite nanotubes (HNTs) were modified by polyaniline (PANI) and then used as nanocontainers to encapsulate the green corrosion inhibitor praseodymium (III) cations (Pr3+), obtaining HNTs@PANI@Pr3+ nanoparticles. A scanning electron microscope, transmission electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis were applied to characterize the formation of PANI and the absorption of Pr3+ cations. The corrosion-inhibiting ability of the HNTs@PANI@Pr3+ nanoparticles for iron sheets and the anticorrosion properties of the nanocomposite coatings were evaluated by the electrochemical impedance spectroscopy technique. The results indicated that the coating containing HNTs@PANI@Pr3+ nanoparticles exhibited excellent anticorrosion performance. After immersion in 3.5 wt % NaCl solution for 50 days, its Zf=0.01 Hz value was still as high as 9.4 × 108 Ω cm2. The icorr value was 3 orders of magnitude lower than that of the pure WEP coating. The excellent anticorrosion property of the HNTs@PANI@Pr3+ coating could be attributed to the synergy of three beneficial factors, including evenly distributed nanoparticles, PANI, and Pr3+ cations. This research will provide theoretical and technical support for the development of waterborne coatings with high corrosion resistance.