Electrochemical and surface characterization studies of winged bean extracts doped TEOS-PDMS sol-gel protective coatings on reinforcing bar in acidic medium

Hybrid sol-gel coatings consisting of tetraethoxysilane (TEOS)-polydimethylsiloxane (PDMS) molecular precursors doped with winged bean extracts were synthesized for the corrosion protection of reinforcing steel in a 0.5 M HCl medium. The incorporation of winged bean extracts doped into hybrid TEOS-PDMS composite coatings on reinforcing steel resulted in a protective system with superior corrosion protection performance, as determined by electrochemical impedance spectroscopy, electrochemical noise measurement and potentiodynamic polarization. When compared to the undoped TEOS-PDMS silanol coating, the corrosion current density and electrochemical current noise resistance values of the winged bean extracts doped hybrid coatings were much lower, whereas charge transfer resistance values were significantly higher. Scanning electron microscopy, Fourier transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy techniques were used to analyse the morphology and structure of developed sol-gel coatings. In addition, atomic force microscopy and wettability analyses were exploited to further understand the characteristics of hybrid silanol coatings. The outcome of this study corroborates that winged bean extracts doped TEOS-PDMS hybrid coatings could be adopted as potential coatings for reinforcing steel.