Study of (3-mercaptopropyl)trimethoxysilane reactivity on zinc: Comparison with organothiol and organosilane thin films

To assess the reactivity of both terminal functions of the (3-mercaptopropyl)trimethoxysilane molecule, three types of zinc substrate (mechanically polished, electrochemically reduced and electrochemically oxidized) were modified concurrently by 1H,1H,2H,2H-perfluorooctyl-triethoxysilane and 1H,1H,2H,2H-perfluorooctanethiol. Surface characterization has been carried out with X-ray photoelectron spectroscopy, polarization modulation infrared reflection–absorption spectroscopy and contact angle measurements. Classical electrochemical techniques were employed to investigate corrosion inhibition of zinc along with thin films grafting. It is found that electrochemical oxidation enhances the grafting of the –Si(OCH3)3 groups while electrochemical reduction facilitates the formation of thiolate bonds, leading both to modified surfaces of much better quality compared to modified polished zinc samples.