Poly(o-phenylenediamine) coatings on mild steel: Electrosynthesis, characterization and its corrosion protection ability in acid medium

Strong adherent electroactive conductive polymer films of poly(o-phenylenediamine) (PoPD) have been electrodeposited on mild steel (MS) by potentiodynamic method using 0.1 M oxalic acid solution in 0.05 M of o-phenylenediamine (o-PD) monomer. Thin, adherent and transparent layers of PoPD contains ladder conductive polymer structure with phenazine skeleton were confirmed by Fourier Transform Infra Red (FT-IR) and Ultra Violet visible (UV–vis) spectroscopy, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) analysis. The corrosion protection performance of the PoPD coatings on MS in 0.5 M hydrochloric acid (HCl) was investigated using Open Circuit Potential (OCP), potentiodynamic polarization and Electrochemical Impedance Spectroscopic (EIS) measurements. OCP and polarization measurements have shown that the MS coated with PoPD maintain the potential in the passive state whereas the uncoated MS exhibit potentials in the active state indicating that significant protection is achieved by the polymer coating. High charge transfer resistance (Rct) and low double layer capacitance (Cdl) values from EIS suggest that the PoPD film exhibits excellent corrosion inhibition behavior on MS in acid environment.