Conducting polyaniline nanocomposite-based paints for corrosion protection of steel

The incorporation of inorganic fillers of different nature and size into conducting polyaniline (PANI)-based paint formulation extends the possibility of developing protective coatings with a self-healing capability and improved corrosion protection performance. The resulting PANI-based coatings are characterized as nanocomposite systems if the filler has nano-size dimensions. Nanofillers such as metal and metal oxide nanoparticles, clay, carbon nanotubes, graphene, and other inorganic pigments combined with PANI give rise to a variety of PANI nanocomposites with interesting properties and potential applications. The present review article concerns applications of PANI nanocomposites in steel anticorrosion technology. The advantages of PANI nanocomposite coatings over the parent polyaniline coating are highlighted. The synergistic effect of PANI and nanofiller leads to enhancement of the mechanical, physical, and chemical properties of coatings allowing the self-healing property of PANI to appear through either the anodic protection mechanism resulting in the oxide repairing at pinholes or the controlled inhibitor release mechanism by which the PANI-based nanocomposite coating liberates corrosion inhibitors (dopant ions) on demand upon the generation of a defect on the coating leading to the oxidation of the metal and hence to the reduction of PANI.