Electrochemical investigations on the corrosion protection effect of poly(vinyl carbazole)-silica hybrid sol-gel materials

A series of solgel derived organicinorganic hybrid coatings consisting of organic poly (vinyl carbazole) (PVK) and inorganic silica (SiO2), with 3-(trimethoxysilyl)propyl methacrylate (MSMA) as coupling agent, were successfully synthesized. First of all, vinyl carbazole (VCz) monomers are copolymerized with MSMA by performing free-radical polymerization reactions with AIBN as initiator. Subsequently, as-prepared copolymer (i.e., solgel precursor) was further reacted with various feeding content of tetraethyl orthosilicate (TEOS) through organic acid (CSA)-catalyzed solgel reaction to form a series of PVK-silica hybrid (PSH) solgel materials. The as-synthesized hybrid materials were subsequently characterized by Fourier-Transformation infrared (FTIR) spectroscopy and solid-state 29Si NMR. It should be noted that the PVK-SiO2 hybrid (PSH) coating on cold-rolled steel (CRS) electrode with low silica loading (e.g., 10 phr) was found to be superior in anticorrosion property over those of neat PVK based on a series of electrochemical measurements such as corrosion potential, polarization resistance, corrosion current, and electrochemical impedance spectroscopy in 3.5 wt% NaCl electrolyte. The better anticorrosion performance of PSH coatings as compared to that of neat polymer may probably be attributed to the stronger adhesion strength of PSH coatings on CRS electrode, which was further evidenced by Scotch tape test evaluation. Increase of adhesion strength of PSH coatings on CRS electrode may be associated with the formation of FeOSi covalent bonds at the interface of PSH coating and CRS electrode based on the FTIRRAS (reflection absorption spectroscopy) studies. POLYM. COMPOS., 2012. (c) 2011 Society of Plastics Engineers