| Corrosion resistance evaluation of a carbon steel disk coated with primer and glass-flake/epoxy paint received from the Esfahan Oil Refinery Company using electrochemical impedance spectroscopy |
| کد مقاله : 1019-CNF |
| نویسندگان |
|
پگاه یانی *1، محمد ژیانی2، محمد محمدی تقی آبادی3، سعید برزی4، محمد کریمی4 1شیمی کاربردی، دانشکده شیمی، دانشگاه صنعتی اصفهان، اصفهان 2گروه آموزشی شیمی فیزیک ، دانشکده شیمی ، دانشگاه صنعتی اصفهان ، اصفهان ، ایران 3گروه آموزشی شیمی فیزیک ، دانشکده علوم پایه ، دانشگاه تربیت مدرس ، تهران ، ایران 4واحد پژوهش و فناوری، شرکت پالایش نفت اصفهان، اصفهان، ایران |
| چکیده مقاله |
| Corrosion prevention is a vital issue that should be given serious attention. Several strategies have been used for this purpose, of which the use of paint and coating with barrier performance is the most common. However, there is no coating with absolutely perfect function, and even the best of them has porosities through which corrosive species can reach the coating/metal interface and cause corrosion of substrate and detachment of the coating [1, 2]. Electrochemical methods, especially electrochemical impedance spectroscopy (EIS), are widely used to evaluate the protective performance of organic coatings on metal [3]. In this study, a carbon steel sample coated with primer and glass-flake/epoxy was received from EORC and its corrosion resistance in salt solution was investigated using EIS and optical microscope images. Electrochemical measurements were conducted on IVIUM potentio-galvanostat controlled by IVIUM software. A homemade three-electrode cylindrical cell filled with 3.5% NaCl solution was used. The exposed surface area of the tested samples was 3.14 cm2. SCE and Pt sheet were used as reference and counter electrodes, respectively. All electrochemical tests were conducted at the open circuit potential (OCP) in a frequency range of 1 MHz-0. 1 Hz with sine wave potential of 0.05 V. At first EIS was conducted twenty minutes after sample immersion and then the immersed sample was kept at 60 °C for 1, 3, 6, and 9 days to accelerate the corrosion mechanism, but before the EIS measurements on each of the above mentioned day, the sample was allowed to reach ambient temperature. Two time constants can be recognized from bode-phase diagrams in Figure 2 that can be interpreted as very low resistance of coating against electrolyte penetration. According to the Nyquist plot in Figure 2, Arc diameter at the start is 160 MΩ.cm2 and decreases approximately 77% on the 3rd, 6th and, 9th day and reaches a much lower value of circa 65 MΩ.cm2 which is an evident sign of coating failure. Also in optical microscope images of the sample, while the substrate looks intact, some pits and non-uniformity are observable on the coating even prior to the immersion (Figure 1a). After 9 days of immersion of the sample, the surface under the coating has some reddish-brown spots, which are clearly the products of corrosion or in other words rust (Figure 1b). |
| کلیدواژه ها |
| Corrosion, Carbon Steel, Glass-Flake Epoxy, EIS, saline water |
| وضعیت: چکیده برای ارائه به صورت پوستر پذیرفته شده است |