Synthesis of graphene oxide functionalized by polyaniline coated alpha-zirconium phosphate to enhance corrosion resistance of waterborne epoxy coating

Abstract Graphene oxide (GO), a preeminent two-dimensional (2D) material, has great potential application for corrosion protection owing to its excellent barrier properties to gas and liquid. Unfortunately, the poor dispersion in waterborne epoxy resins and excessive surface defects limit the further application of GO. In this study, a novel GO-based nanofiller PZ-GO (GO modified by polyaniline-wrapped alpha-zirconium phosphate) was designed to endow waterborne epoxy coating (WEC) system with durable anti-corrosion performance. Among them, the modification of alpha-zirconium phosphate (α-ZrP) wrapped with polyaniline (PZ) for GO not only enhanced the dispersion of GO but also strengthened its barrier effect. Notably, as a linker between GO and α-ZrP, PANI could also endow the coating with active inhibition performance. Differential scanning calorimetry (DSC) was introduced to investigate the effect of adding nanofillers on ‘Cure Index’ of composites. The ‘Cure Index’ of epoxy resins doped with PZ-GO was 1.139, which was considered as ‘Excellent’ according to the evaluation criteria, proving that the addition of PZ-GO significantly reinforced the curing degree of epoxy resins. A more complete cure of the epoxy resins could provide a stronger barrier ability for the coatings, thus improving the corrosion resistance of the coatings. Furthermore, the anticorrosive behavior of PZ-GO/WEC was analyzed via electrochemical impedance spectroscopy (EIS) and salt spray tests. The results showed that PZ-GO/WEC exhibited great anticorrosive performance (the impedance value was maintained at 8.72 ×107 Ω.cm2 after immersion in 3.5 wt% NaCl solution for 80 days). In particular, PZ-GO/WEC also demonstrated great active inhibition performance. In addition, the active inhibition mechanism of PZ-GO/WEC was revealed by X-ray photoelectron spectroscopy (XPS) analysis of the corrosion products. All results proved that the excellent corrosion protection properties of PZ-GO/WEC for carbon steels originated from the outstanding barrier ability of PZ-GO/WEC and the active inhibition of PANI.