Tamarind shell tannin-doped hybrid sol-gel coatings on mild steel in acidic medium toward improved corrosion protection

This study investigated the application of tamarind shell tannin extracts (TSTE) [isolated using methanol (TME) and 70% acetone (TAE)]-doped hybrid sol-gel coatings prepared using (3-Glycidyloxypropyl)trimethoxysilane (GPTMS) and tetraethoxysilane (TEOS) in 0.5 M HCl solution. The anticorrosion properties of these hybrid coatings on the surface of mild steel electrodes were described using potentiodynamic polarization (PD) and electrochemical impedance spectroscopy (EIS) measurements. The hybrid sol-gel coatings were characterized via FTIR. Also, the hydrophobicity of the coated plates was determined through water contact angle measurement. Meanwhile, the surface morphology and elemental compositions were determined using SEM/EDX analyses. The electrochemical measurements showed that the mixture of doped TME and TAE hybrid sol-gel coating resulted in higher corrosion resistance. The corrosion inhibition efficiency (CE) was CETME = 94.02% and CETAE = 91.35%, respectively. The Tafel slopes revealed a mixed form of corrosion protection with the main effect at cathodic sites. FTIR absorption bands attained at 945 cm(-1) for TME and 961 cm(-1) for TAE revealed Fe-O-Si bond formation. The higher corrosion inhibition capability of the coating matrix corroborates to higher water contact angle (theta(TME) = 107.64 degrees, theta(TAE) = 104.62 degrees) values. SEM analysis revealed coatings' improved corrosion protection due to the doping's enhanced inhibitive performance.

Automated summary

The study found that the mixture of doped TME and TAE in hybrid sol-gel coatings can improve the anticorrosion properties of mild steel electrodes, resulting in higher corrosion inhibition efficiency.