The Conductivity Behaviour of Acid-Doped PANI and its Effect on the Corrosion of Mild Steel in HCl

• Published in: Malaysian Journal of Chemistry
• Main Author: Zainuddin N.; Tarmizi A.A.A.
• Format: Article
• Language: English
• Published: Malaysian Institute of Chemistry 2024
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85214675493&doi=10.55373%2fmjchem.v26i6.136&partnerID=40&md5=09cefd05813961890d4298dd497df0bd

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. © 2024 Malaysian Institute of Chemistry. All rights reserved.