Electrodeposition and corrosion protection properties of conducting PEDOT coatings on steel electrode

Conducting polymers (CPs), such as poly(3,4-ethylenedioxythiophene) (PEDOT), are widely recognized for their exceptional electrical conductivity, chemical stability, and environmental durability, making them promising candidates for protective coatings on metal surfaces. In this study, PEDOT coatings were electrochemically deposited on mild steel and platinum electrodes using cyclic voltammetry (CV) in a non-aqueous acetonitrile medium containing tetrabutylammonium hexafluorophosphate. The deposition conditions—including scan rate, initial and final potentials, monomer concentration, and temperature—were optimized to achieve a homogeneous, compact, and adhesive polymer layer. The optimal conditions involved an EDOT monomer concentration of 0.01 M, a scan rate of 100 mV/s, and a potential range from − 0.5 to 1.8 V (SCE) at 30 °C. The electropolymerization process was found to be more efficient on steel (activation energy, E_a = 10.894 kJ/mol) than on platinum (E_a = 49.426 kJ/mol), resulting in a denser PEDOT film with lower activation energy. Fourier transform infrared spectroscopy (FTIR) confirmed successful polymerization, while scanning electron microscopy (SEM) revealed distinct morphological differences between PEDOT coatings on steel and platinum surfaces. Corrosion studies in HCl and H₂SO₄ solutions demonstrated that PEDOT-coated steel exhibited substantially enhanced corrosion resistance compared to uncoated steel, achieving a protective efficiency of up to 66% after 24 h of immersion. Electrochemical impedance spectroscopy (EIS) further highlighted the superior barrier properties of PEDOT, emphasizing its ability to prevent corrosion by forming an effective barrier layer and promoting the formation of a passive film beneath the coating.

Graphical abstract