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 (HNO 3 ), and phosphoric acid (H 3 PO 4 ). 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 HNO 3 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.