Enhanced corrosion inhibition of low carbon steel in aqueous sodium chloride employing sol–gel-based hybrid silanol coatings

The anti-corrosion properties of sol–gel-based hybrid silanol coatings incorporated with span tea leaves extract employed on low carbon steel in saline solution was explored by electrochemical and surface analyses. Hybrid sol–gel matrices were prepared by copolymerizing tetraethyl orthosilicate (TEOS) and 3-aminopropyltriethoxysilane (APTES). Corrosion protective hybrid sol–gel coatings were dip-coated on low carbon steel substrates and sintered to ensure the formation of metallo-siloxane bonds. Inhibition efficiency of 85.66% was achieved with the doping concentration of 75 ppm of water extract into hybrid sol–gel at 30 °C. Polarisation studies demonstrated that the hybrid coatings incorporated with water extract of span tea leaves operate as a mixed-type inhibitor. The Nyquist impedance plots depicted that on increasing the concentration of span tea leaves extract, charge transfer resistance (Rct) increased, and double-layer constant phase element (CPEdl) decreased. A comparison of the corrosion resistance of the coated and uncoated low carbon steel substrates was presented. Electrochemical noise analysis substantiated that the optimum corrosion-resistant coating formulation endured a much lower current noise fluctuation. Moreover, wettability analysis established the hydrophobic nature of the optimum corrosion protective coating.