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. [ABSTRACT FROM AUTHOR]