Poly p-phenylendiamine–SiO2 nanocomposite (PSC) was prepared by oxidative polymerization of p-phenylendiamine in hydrochloric acid with ammonium persulfate in the presence of SiO2 nanoparticles. The results of atomic force microscopy confirm that the surface is smoother for the case of epoxy=PSC=steel. The smoothness of epoxy=PSC=steel is due to the formation of a compact protective coating that inhibit the corrosion of steel. The coatings on steel were evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy in 1M HCl solution. Results indicated that the coating having PSC can protect the steel more efficiently than the coating containing sole poly p-phenylendiamine
