Chitosan-polypyrrole-SiO2 composite coatings with advanced anticorrosive properties

Chitosan-polypyrrole-SiO2 composites were synthesized by chemical oxidative polymerization of pyrrole in chitosan solution using FeCl3 as an oxidant. The synthesized composites were loaded in epoxy resin and subsequently coated on mild steel substrate using powder coating technique. XRD and FTIR analyses show interaction between chitosan and polypyrrole. Microstructural analyses reveal the formation of polymer particles with distinct spherical morphology. SiO2 particles embedded in the polymer matrix are clearly noticed from the FESEM micrographs. TGA thermogram shows good thermal stability of chitosan-polymer composite. DSC curves reveal a high cross linking density for epoxy coatings loaded with chitosan composite. Tafel plots exhibit significantly high corrosion protection efficiency (99.99%) for the epoxy coatings with 2.0 wt% loading of chitosan-polymer composite. The weight loss measurements and salt spray test results clearly exhibit superior corrosion resistance offered by coatings with chitosan-polymer composite. The synergistic interaction between the chitosan and the polypyrrole in the composite is expected to improve the corrosion resistance properties of the coatings. The SiO2 particles present in the composite reinforce the integrity of the coating under corrosive conditions.