Comparative anti-corrosion properties of alkylthiols SAMs and mercapto functional silica sol–gel coatings on copper surface in sodium chloride solution

In this paper, we tried to fabricate a compact and thick mercapto functional silica sol–gel coating to achieve excellent corrosion resistance performance on copper. A detailed comparative study of alkylthiol self-assembled monolayers (SAMs) and mercapto functional silica sol–gel coating prepared by 1-octanethiol, n -dodecanethiol and (3-mercaptopropyl)trimethoxysilane (MPTMS) was carried out. The elements composition and chemical bonding of the protective coatings were characterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. In addition, the cross section morphologies of Cu–MPTMS sol–gel coating were investigated by field emission scanning electron microscopy. The wettability of various coatings was investigated by contact angle measurement instrument. Finally, the anti-corrosion ability of the coatings was characterized using an electrochemical workstation. Results demonstrated that compared to other alkylthiol SAMs, the Cu–MPTMS sol–gel coating showed the best anti-corrosion property in sodium chloride solution because it owned a multiple hierarchic Si–O–Si network structure, thus to achieve a higher range of thickness and lengthen the diffusion path way of corrosive medium. It was also found that compact and thick mercapto functional silica sol–gel coating shows better corrosion resistance performance than other SAMs of the same type.