Novel Additive-Included Hybrid Sol–Gel Coatings for Practical Corrosion Protection of Carbon Steel in a Saline Medium

A hybrid sol–gel coating was synthesized by mixing tetraethylorthosilicate and triethoxyvinylsilane to protect St37 steel in 3.5 wt.% NaCl solution. The prepared coating was characterized using Fourier transform infrared spectroscopy, x-ray diffraction, and scanning electron microscopy. To improve the protection ability of the proposed coating, two pigments, including bromophenol blue and eosin-methylene blue, were added to the coating as corrosion inhibitors. The influence of multi-walled carbon nanotube as the surface modifier on the performance of the coating was also investigated. Corrosion tests were performed by electrochemical impedance spectroscopy. The results obtained indicated that the presence of each of the inhibitors in the coating resulted in a slight improvement in corrosion protection. However, the simultaneous addition of the nanoparticle and inhibitor into the coating made a significant increase in the corrosion resistance of the coating.