DOI: https://doi.org/10.55373/mjchem.v26i6.136

Keywords: Polyaniline (PANI); conductivity; dopants (acid); inhibitor; corrosion

Abstract

This study investigates how dopant acids affect the properties and electrical conductivity of polyaniline (PANI), and addresses the gap in understanding the conductivity behaviour of PANI-doped acids and their effects on the corrosion of mild steel in HCl. PANI was synthesized by chemical oxidative polymerization using sulfuric acid (SA) and oxalic acid (OA), with ammonium persulfate as the oxidant. Characterization via FTIR and SEM revealed successful doping, as indicated by the appearance of new bands in the conductive polymer and the disappearance of the aniline N-H signal at the 3500 to 3200 cm-1 frequency range. Morphological analysis showed that higher concentrations of dopants offered more consistent, smooth and efficient corrosion protection for mild steel. Corrosion performance was assessed using weight loss measurements, and conductivity was analysed by electrochemical impedance spectroscopy (EIS). The results demonstrated that higher concentrations of dopants significantly enhanced conductivity, with SA and OA showing values of 1.015×10-3 S/cm and 330×10-3 S/cm, respectively. PANI doped with 0.1 M OA exhibited the highest inhibitor efficiency (IE) of 15.41 %. The formation of a passive oxide layer likely contributed to lower IE percentages. EIS, conducted to analyse the inhibitor’s effects on corrosion, indicated that the protection provided by PANI-doped acids was due to the passive oxide layer, as evidenced by higher impedance values and two capacitive loops after 72 hours.