Electrochemical Deposition of Zinc/Nickel Multilayer Coating and Investigating the Effect of Morphology and Phase Structure on the Dissolution of Zinc/Nickel Alloy Coating

Tahmasebi, Maedeh | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55493 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Ghorbani, Mohammad
  7. Abstract:
  8. The multilayer coating (Zn-Ni)1/(Zn-Ni)2 is deposited from a single bath with a zincate-sulfate compound and by changing the current density. The effect of current density and the number of layers on the chemical composition, surface morphology, roughness, phase structure, and corrosion resistance of multilayer coatings respectively using atomic absorption spectroscopy, FE-SEM microscope, roughness tests, X-ray analysis, and electrochemical techniques such as Tafel polarization and impedance was investigated and compared with single-layer coatings. Because the amount of nickel in the composition of the coatings is less than 27%, in all the studied currents, the deposition is anomalous. The corrosion current density of the eight-layer (Zn-Ni)1/(Zn-Ni)2 coating is about 0.1 times that of the single-layer zinc-nickel coating deposited at a current density of 60 mA/cm2, and with the increase in the number of layers, the roughness OF coatings also improved by about 45% compared to the monolayer coating deposited at 10 mA/cm2 current, so the multilayer-ing leads to the formation of a finer morphology as well as less roughness. The electrical circuit that was proposed to model the corrosion process based on electrochemical impedance spectroscopy proved that multilayering reduces the porosity of the coatings and thus improves the properties of the barrier layer. Also, to remove the bubbles during deposition, the final coating was done in the presence of ultrasonic waves, and the corrosion properties, in this case, were also improved by about 40% compared to the absence of ultrasonic waves
  9. Keywords:
  10. ZINC ; Nickel ; Multi-Layer Coating ; Alloy Coating ; Electrochemical Deposition ; Zinc-Nickel Coat ; Ultrasonic Waves ; Coating Morphology

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