The corrosion resistance enhancement of magnesium alloy through creating plasma electrolytic oxidation-layered double hydroxide nanocomposite coating in phosphate bath

نوع: Type: Thesis

مقطع: Segment: masters

عنوان: Title: The corrosion resistance enhancement of magnesium alloy through creating plasma electrolytic oxidation-layered double hydroxide nanocomposite coating in phosphate bath

ارائه دهنده: Provider: Hossein Ghadimi

اساتید راهنما: Supervisors: Dr. Omid Imantalab

اساتید مشاور: Advisory Professors: Dr. Arash Fattah Al-Hosseini _ Dr. Mazdak Izadi

اساتید ممتحن یا داور: Examining professors or referees: Dr. Mohsen Sheikhi _ Dr. Ismail Damavandi

زمان و تاریخ ارائه: Time and date of presentation: 2025

مکان ارائه: Place of presentation: 71

چکیده: Abstract: The primary objective of this research is to develop plasma electrolytic oxidation (PEO) nanocomposite coatings incorporating layered double hydroxides (LDH) to enhance the electrochemical behavior of AZ31B magnesium alloy in chloride-ion-containing environments. Characterization of the fabricated coatings was performed using X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM) images, energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), roughness and wettability tests, potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS). To achieve the research goal, Zn-Al-LDH was first synthesized via a hydrothermal method. Subsequently, nanocomposite coatings were produced in the presence of varying concentrations of the synthesized LDH (0.50, 0.75, and 1.00 g/L) at a current density of 7 A/dm², a duty cycle of 50%, a frequency of 100 Hz, a duration of 7 minutes, using a phosphate electrolyte under direct current conditions on AZ31B substrates. Electrochemical test results indicated that the incorporation of LDH into the phosphate-based coating electrolyte improved the electrochemical behavior of the nanocomposite coating compared to the PEO coating formed in a phosphate electrolyte without LDH. Additionally, increasing the LDH content in the coating electrolyte further enhanced the electrochemical performance of the resulting coatings. Electrochemical tests revealed that the primary role in corrosion protection of the fabricated coatings is attributed to the compact inner layer. Moreover, the presence of LDH influenced the EIS behavior of the coatings, such that inductive behavior was not observed in coatings containing LDH. The improved electrochemical behavior of the coatings with increased LDH content in the coating electrolyte can be attributed to increased hydrophobicity, reduced roughness, decreased porosity, and the inhibitory effect of LDH against the penetration of aggressive anions towards the substrate. Considering all experimental results of the present study, the use of LDH to enhance the performance of oxide films produced by the PEO process on magnesium alloys can lead to the development of these alloys for orthopedic and implant applications

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