Polydopamine wrapped polyaniline nanosheets: Synthesis and anticorrosion application for waterborne epoxy coatings

Two-dimensional materials have been proved to be effective in improving the performance of anticorrosive coatings. However, most of the reported two-dimensional materials only have the ability to passively block corrosive media and cannot effectively inhibit localized corrosion reactions at the metal/coating interface. Herein, we first synthesized a novel polyaniline (PANI) nanosheet with both barrier and passivation functions for metals. In addition, polydopamine (PDA) wrapped PANI nanosheets (PANI@PDA) were obtained by in situ self-polymerization reaction of dopamine on the PANI surface, which enhance its interfacial interaction with polymeric resin. The chemical structure, morphology and corrosion inhibition properties of the nanosheets were systematically analyzed. The incorporated PANI@PDA nanosheets in composite coating provide a longer penetration path for corrosive mediums. Secondly, the uniformly dispersed two-dimensional nanosheets induce the formation of passivation film on the metal substrate. The protective effect of PANI@PDA nanosheets on coatings was verified by electrochemical impedance spectroscopy (EIS). Results indicated that the prepared composite coating exhibited excellent corrosion resistance throughout the test cycle. This simple and effective modification strategy based on conductive polymers provides a new insight into the development of environmentally adaptive composite coatings with active and passive protection.