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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 43891 (07)
- University: Sharif University of Technology
- Department: Materials Science and Engineering
- Advisor(s): Ghorbani, Mohammad
- Abstract:
- Alloy coating of nickel - molybdenum with 20-25 wt% Mo, exhibits excellent protective properties against corrosion in different corrosive environments, therefore it has received much attention. In comparison with Ni coatings, Ni-Mo coatings reduce hydrogen evolution reaction overpotential(HER) significantly, therefore it has suitable catalytic properties for HER.
A few researches on pulse reverse palting of Ni-Mo coatings have been published. in this work, we have evaluated effects of PRC on some properties of Ni-Mo coating such as chemical composition, morphology, catalytic properties for HER, crystaline structure and hardness property. The results of atomic absorption spectroscopy(AAS) show that increase in anodic current density, first causes increase in Mo content of Ni-Mo coating to 35% and then keeps it constant about 67%. Figures of scanning electron microscopy(SEM) show that PRC especially at anodic current density 200 mA.cm-2, has significant effect on modification porphology, decrearsing grain size and increasing prosity. Electrochemical studies such as Electrochemical impedance spectroscopy(EIS) and Polarization test show that PRC has twofold effect to improve or deteriorate HER and corrosion properties, structure crystallinity and hardness. Among all PRCs, the best results was related to coating which precipitated under anodic current density 200 mA.cm-2. It's corrosion resistance polarization and hardness was respectively 1767 Ohm and 439 Vickers. Among coatings with constant Mo content about 25%, maximum corrosion resistance polarization about 1476 Ohm was related to coating precipitated by pulse current method and the best catalytic propertis and maximum hardness about 613 vickers was related to coating precipitated by direct current method - Keywords:
- Corrosion Resistance ; Electrodeposition ; Hydrogen Evolution Reaction ; Nickel-Molybdenum Alloy Coating ; Pulse Reverse Current (PRC)
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