The co-polymerization of aniline with p-nitroaniline has been synthesized in oxalic acid medium, here ammonium persulfate (APS) acts as an oxidant. TGA analysis was used to study the thermal stability of the copolymer, as well as FTIR, UV–Vis spectroscopy, and XRD. The synthetic poly (aniline-co-p-nitroaniline) (PANA) is used as a barrier/redox pigment for PANA coatings. The anti-corrosion study on PANA coatings was performed with a 3% NaCl solution for up to 35 days. The coating resistance of PANA coatings is three orders of magnitude more than that of pure epoxy coatings, according to the results of electrochemical impedance spectroscopy (EIS). The scanning vibrating electrode method (SVET) was used to investigate the self-healing characteristics of this PANA coating. Display omitted •The poly (aniline–co-p-nitroaniline) (PANA) is prepared by a chemical oxidation route.•The PANA doped oxalate ion acts as an inhibitor at the onset of corrosion.•The corrosion protector of PANA was studied by EIS.•The imitated corrosion process of PANA was studied by SVET.•The superior corrosion protection of PANA is better than epoxy coating.