Research In Preparation And Corrosion Resistance Of Self-assembled Monolayer Of Alkanecarboxylic Acid On Copper

Self-assembled monolayer(SAM) is highly ordered, and close-packed molecular film, which forms through spontaneous chemisorption of active molecules onto solid surface. SAM provides a convenient technique to modify surfaces under mild conditions, which is currently widely studied. SAM has a broad application prospects of protecting the metal substrate from corrosion under different corrosive environments.Copper, with good electrical conductivity and thermal conductivity, is a metal widely used in chemical and electronics as well as building industries, so the research on corrosion of copper is an important research topic. Because copper surface can easily be oxidized in the atmosphere, which reduces the interaction of active molecules and copper, it is difficult to prepare SAM on copper. However, it is of both theoretical and practical importance to study the protection ability of SAM of alkanecarboxylic acid to the underlying copper substrate in corrosive solutions.The interaction of active molecules and copper is weak, therefore in order to improve the binding force of copper and SAM of alkanecarboxylic acid, in this dissertation, Cu(OH)2 nanorod quasi-arrays/CuO microflowers hierarchical structures were fabricated on copper substrates via alkali assistant surface oxidation technique, and then we prepared stearic acid(STA) and oleic acid(OA) SAM on the hierarchical structure surface. The formation of stearic acid and oleic acid SAM is susceptible to environmental factors. Therefore, in order to obtain dense and stable SAMs and improve their corrosion resistance, we selected optimal concentration and immersion period for formation of STA and OA SAM by using a simple and convenient electrochemical impedance spectroscopy(EIS) method.The results showed that:under the same conditions, the inhibition efficiency increased with increase in concentration of stearic acid and oleic acid and immersion time in a certain range; STA SAM had superior corrosion resistance than OA SAM. The paper also had a more detailed characterization of corrosion protection properties of STA and OA SAM in 0.1M NaCl solution using the polarization curve and cyclic voltammetry to clarify the inhibiting mechanism of STA and OA SAM. The SAM could act as hydrophobic barrier layer, which effectively prevented the copper substrate from contacting with corrosive ions, thereby inhibiting the copper corrosion to a considerable degree. Fourier transform infrared spectrosc- opy and contact angle measurements showed that the order and hydrophobicity of the STA SAM were higher than those of OA SAM, and so STA SAM had superior corrosion resistance than OA SAM. By quantum chemical calculations, C=C double bond and carboxyl of oleic acid competed to adsorb onto CuO/Cu(OH)2 surface, the two different reactions active sites was not conducive to the order of alkyl chain in OA SAM.