Synthesis of PDA-rGO/MoO3 nanohybrids for distinguishable anticorrosion enhancement of waterborne epoxy coating

Waterborne epoxy (WEP) resins have gained considerable attention for their environmentally friendly characteristics. Nevertheless, they are susceptible to substantial failures due to electrochemical corrosion, particularly when the coating is compromised or exposed to harsh corrosion environments. Furthermore, its long-term anticorrosive performance is affected by certain inherent defects. In this study, inspired by the adhesive properties of mussels, polydopamine (PDA) was used as a green binder to integrate graphene oxide (GO), h-MOO3, and WEP matrix, creating a uniform three-dimensional (3D) network structure. PDA-modified two-dimensional GO nanosheets can also create a porous carrier capable of loading anticorrosive Mo derivatives, imparting self-healing properties that enhance anti-corrosion performance. The resulting composites exhibited remarkable self-healing ability due to the unique design of the PDA-rGO porous structure infused with anticorrosive MoO3. Subsequently, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and ultraviolet-visible spectroscopy were used to confirm the PDA-rGO/MoO3 nanostructure. The results confirmed the successful self-polymerization of PDA on the GO surface, converting it into reduced GO (rGO). Then PDA-rGO/MoO3 composite WEP coatings were systematically evaluated by electrochemical impedance spectroscopy (EIS), microscopy and acceleration corrosion experiment. In addition, electrochemical impedance spectroscopy (EIS) and microscopy were used to assess the PDA-rGO/MoO3 composite coatings. The EIS results revealed that the composite coating with 0.5 wt% PDA-rGO/MoO3 substantially enhanced the anti-corrosion performance compared with the control samples. After prolonged immersion for 60 days in a 3.5 wt% NaCl solution, the composite coating exhibited outstanding anti-corrosion performance, surpassing that of the GO/WEP coating by three orders of magnitude. This composite nanocoating provides valuable insights into the design of well-dispersed, 3D network-structured coatings with self-healing properties for corrosion protection, which opens up new possibilities for the practical application of composite nanohybrids in the field of anti-corrosive coatings.