Characterization and corrosion inhibition studies of protective sol-gel films modified with tannin extracts on low carbon steel

In the present work, tannins extracted from tamarind shells using water (TWE) and ethyl acetate (TEAE) were introduced into fabricated sol-gel containing 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetraethoxysilane (TEOS) which were subsequently assembled over mild steel surface. The corrosion inhibitive behavior of the prepared layers in 0.5 M HC1 was experimented by exploiting potentiodynamic polarization and electrochemical impedance spectroscopy analyses. Optimized GPTMS-TEOS alkoxysilane films' functional groups were corroborated exploiting Fourier transform infrared spectroscopy. Surface morphology, elemental composition and wetting property of the optimized coatings were explored via scanning electron microscopy, energy dispersive X-ray spectroscopy and wetting angle studies, respectively. The result of the electrochemical studies revealed that the maximum inhibition efficiency achieved at 1000 ppm was up to 90%. With regards to FTIR spectra, the infrared bands at -1046 and -935 cm(-1) confirmed the formation of (Si-O-Si) and (Fe-O-Si) covalent bonds. The presence of this peak indicates the formation of networks between the mild steel substrate and silicate. The study has revealed that tannins doped GPTMS-TEOS silanol matrix enhanced the protection ability by promoting crosslinking reactions of the coatings compared to undoped coatings to a significant extent. [GRAPHICS] .

Automated summary

In this study, tannins extracted from tamarind shells were used to test their corrosion inhibitive behavior on mild steel surfaces. The results showed that tannins-doped coatings exhibited good inhibition efficiency and promoted crosslinking reactions of the coatings.