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plasma Electrolytic Oxidation of AZ31 in Silicate and Phosphate Electrolyte and Study of Corrosion Behavior

Sharifi, Hassan | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 47384 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Ghorbani, Mohammad
  7. Abstract:
  8. In recent years, magnesium and its alloys have been considered as biodegradable implants, but they corrode in the body before natural process of damaged organs recovery is completed. In this investigation PEO operation was used for corrosion control and effect of different parameter such as number of operation steps, electrolyte type, time and operation voltage on coating properties was studied. Scanning electron microscopy was used for investigating of morphology of coats and to determine chemical composition and phase of coats EDS analysis and X-ray diffraction were used. The corrosion resistance of samples were evaluated by potentiodynamic polarization and electrochemical impedance (EIS) tests and immersion in simulated body fluid (r-SBF) at 37 ° C. One step PEO operation was conducted in silicate, phosphate and silicate-phosphate electrolyte in 240 volt and operation time was 15 minutes, and tow step operation was conducted in silicate electrolyte in 240 volt and phosphate electrolyte in 270 volt and operation time was 15 minutes for each process (SP). Two steps operation was repeated by replacement of electrolytes (PS). Results of investigation indicated that the best corrosion resistance was 0.5 µA/cm2 in tow steps operation (SP). Effect of different voltage 220, 240 and 260 volt for first step was studied in 10 minutes operation time where in which the coating formed in 240 volt has the best corrosion resistance (0.4µA/cm2). Also the effect of operation time was investigated in tow step process in which the 15 minutes operation was the best time in which corrosion resistance was 0.5µA/cm2
  9. Keywords:
  10. Biodegradability ; AZ31 Magnesium Alloy ; Plasma Electrolytic Oxidation ; Two Stage Plasma Electrolytic Oxidaition (PEO) ; Reverse-solution Body Fluid (r-SBF)

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