| Summary: | 碩士 === 中國文化大學 === 化學工程與材料工程學系奈米材料碩士班 === 107 === The purpose of this research is to investigate the electrochemical corrosion characteristics of high-entropy alloy FeCoCrNiMox (x=0, 0.3, 0.7, 1.0) in hydrofluoric acid and fluoride salt. The HEA composition is similar to 316 stainless steel on the market ; the major components Fe. The addition of chromium (Cr) contributes to the formation of a passive film, and the addition of molybdenum (Mo) can effectively resist the pitting of chloride salts. It is interesting to know that the difference may find in the fluoride environments. From the results of XRD analysis, it is observed that when -Mo content between 0 and 0.3, it is a single FCC phase, and when the -Mo content is≧0.7, a large amount of HCP phase appears. As the Mo content increases, the hardness of the alloys is increased unequivocally using a microhardness tester.
In this experiment, four kinds of alloys were prepared by arc melting and electrochemically measured by a potentiostat. Anodic polarization curves were obtained in hydrofluoric acid and its sodium salt in three concentrations (0.01M, 0.1M, 1M) to determine all relevant corrosion parameters of the alloy, such as corrosion potential, corrosion current density and passive current density through the potential dynamic polarizations. Use the Electrochemical Impedance Spectroscopy(EIS) in terms of Nyquist and Bode plots to establish an equivalent circuit to simulate the interface electric double layer structures. Both SEM and EMPA were employed for the corroded surface analysis both quantitatively and qualitatively.
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