Coatings Corrosion Resistance of Poly(o-Phenylenediamine) on Mild Steel in 3.5% NaCl: Influence of Inorganic Acid

Poly(o-phenylenediamine) was synthesized in different inorganic acid media, hydrochloric (HCl), nitric (HNO3), and phosphoric acid (H3PO4). The aim was to investigate the protective effect of doped coatings on mild steel in an aggressive environment. The synthesized doped-PoPD products were characterized by x-ray diffractometry, Fourier transform infrared spectroscopy, scanning electron microscopy, and cyclic voltammetry. The inhibition abilities of doped coatings were evaluated by potentiodynamic polarization measurements and electrochemical impedance spectroscopy in 3.5% NaCl solution. In the present article, the lowest corrosion current and highest protection efficiency of the doped polymer were observed for the polymer synthesized in HNO3 medium. The results showed that good protection of mild steel can be achieved by PoPD coating doped with inorganic acid in 3.5% NaCl solution.