| The430stainless steel (430SS) has a great demand in society, but it’s susceptible to corrosion limits the application in high-end commodities. Self-assembly technology is a kind of simple and environmentally friendly method used to enhance anti-corrosion property of metal effectively. Alkylsilane SAMs, as a new environmentally friendly technique, are expected to replace the traditional toxic coatings such as the chromium and phosphate coatings mainly due to the excellent corrosion inhibition performance and its non-toxicity. However, studies about silanes self-assembled on the430stainless steel surface were rarely reported. Therefore, this research work was conducted in my master thesis.The adsorption behavior and the corrosion inhibition performance of both alkylsilane and fluoroalkylsiane SAMs were studied by electrochemical measurement, Electrochemical Impedance Spectroscopy (EIS), Attenuated Total Reflection-Fourier Transform Infrared spectroscopy (FTIR-ATR), static contact angle measurements, Scanning Electron Microscopy (SEM), Atomic Force Microscopy(AFM) and X-ray Photoelectron Spectroscopy(XPS).Our main researches are shown as following:1. The self-assembled monolayers(SAMs) of n-Dodecyltriethoxysilane (DTES) and1H,1H,2H,2H-Perfluorodecyltriethoxysilane (PFDS) were successfully prepared on the surface of430stainless steel (430SS) by treatment in assembly solution. The FTIR-ATR results demonstrate that DTES and PFDS were chemically adsorbed on430SS surface by forming Fe-O-Si bonds. The static contact angle tests reveal that PFDS SAMs present stronger hydrophobicity than DTES SAMs do. The potentiodynamic polarization experiment explore that alkali pretreatment and adding water to assembling solution are beneficial for the improvement of corrosion inhibition performances of DTES and PFDS SAMs. The most suitable temperature and time period for treatment to reach the balance between adsorption and desorption of silane molecules on430SS is25℃and2hrs respectively. The following curing process seems to be helpful for forming more Si-O-Si groups which enhance the corrosion inhibition performance, which was confirmed by SEM measurement. The DTES SAMs reach the highest density with the concentration of10mM of DTES, while the highest density of PFDS SAMs could be obtained at higher concentration of PFDS. With the combination of the results of potentiodynamic polarization measurement, contact angle measurement and morphologies by AFM, it was found that both DTES and PFDS are anode corrosion inhibitors, however PFDS SAMs has higher inhibition efficiency and stronger hydrophobicity than DTES SAMs.2. The pretreated430SS substrates were immersed in the1H,1H,2H,2H-Perfluorodecyltriethoxysilane (PFDS) solution to form SAMs, which are named as TEOS+PFDS SAMs and Na2SiO3+PFDS SAMs according to the pretreating solutions, tetraethoxysilane(TEOS) and Na2SiO3, respectively. The potentiodynamic polarization test and EIS reveal that the pretreatments by both TEOS and Na2SiO3solution are beneficial to form SAMs and enhance the corrosion inhibition performance. XPS test shows that a large number of Si-OH groups were derived from SiO2layer formed on430SS surface if pretreated in both TEOS and Na2Si03solution, and Si-OH groups had chemical interaction with active groups on430SS. It was also found that Na2SiO3+PFDS SAMs have a larger number of Si-OH groups than TEOS+PFDS SAMs and Na2SiO3+PFDS SAMs show a higher corrosion inhibition performance than TEOS+PFDS SAMs, which might be caused by higher density of Na2SiO3+PFDS SAMs.3. Our research prove that environmentally friendly silane SAMs, DTES and PFDS directly self-assembled on the430stainless steel surface and PFDS indirectly self-assembled on the430stainless steel surface pretreatment by TEOS and Na2SiO3solution, have good density and present excellent corrosion inhibition effect. Silane, as a new type of steel corrosion system, is expected to become one of the candidates to replace chromate and phosphate. |
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