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.