Preparation of Polyaniline-Clay Nanoadditive and Investigation on Anticorrosion Performance in Epoxy Coating

The corrosion protection of mild steel by a newly developed epoxy-based coating system containing inherently conducting nanopolyaniline-clay as a nanoadditive has been studied. Polyaniline-clay anticorrosion nanoadditive (PCNA) was obtained by the direct mixing method of nanopolyaniline (0.03 wt.%) and organo-modified clay (3 wt.%) at atmospheric pressure, and XRD technique was used to study d-spacing of clay platelets in the prepared nanoadditive. PCNA was dispersed in polyaminoamide hardener matrix and was used for epoxy coating (EPCNA) preparation. The particle size of the polyaniline in hardener was determined using dynamic light scattering technique (DLS). The results revealed that the particles were in the range of 50–58 nm. The degree of exfoliation and distribution and particles size were studied by XRD and TEM in the final dried film. The corrosion protection ability of EPCNA was compared to an epoxy coating containing pure nanopolyaniline (ENPN) using electrochemical impedance spectroscopy (EIS) and salt spray methods. In addition, an investigation on the morphology of metal-coating interface by scanning electron microscopy (SEM) technique in ENPN and EPCNA samples after salt spray test showed stable oxide layer formation for ENPN and a dense stable oxide layer for EPCNA on metal surface. The results showed that the PCNA nanoadditive enhanced corrosion protection effect in comparison to pure nanopolyaniline (NPN) in the epoxy coating.