Hybrid sol-gel silane composite coating reinforced with a hybrid organic/inorganic inhibitive pigment: Synthesis, characterization, and electrochemical properties

Abstract

This work aims to develop environmentally friendly silane coating reinforced with a hybrid pigment to protect mild steel against corrosion in a saline environment. Fourier-transform infrared (FT-IR) spectroscopy, contact angle (CA) measurement, field emission scanning electron microscopy (FE-SEM), and energy dispersive spectroscopy (EDS) were used to study the coating structure and its protective mechanisms. The presence of hybrid pigment led to the conversion of more Si–OH groups into Si–O–Si groups during condensation process increasing the cross-linking density of silane; the enhanced cross-linking yields the coating with lower defects and stronger adhesion to substrate and so improved barrier and anti-corrosion properties. The EIS test showed that the charge transfer resistance (Rct) for the sample coated with hybrid sol-gel silane increases up to 40 % for all immersion times after the incorporation of the hybrid pigment into the coating matrix. The polarization test showed that the corrosion current density (icorr) value decreases from 1.40 to 0.56 μA/cm2 after 120 h of exposure to the saline solution when the hybrid pigment is added to the coating matrix. These results demonstrate the inhibitive action of the hybrid pigment enhancing the protective performance of the sol-gel silane coating.