The effect of strontium and chromium element doping on the corrosion behavior and photocatalytic properties of plasma electrolytic oxidation coatings on AZ31B magnesium alloy

نوع: Type: Thesis

مقطع: Segment: PHD

عنوان: Title: The effect of strontium and chromium element doping on the corrosion behavior and photocatalytic properties of plasma electrolytic oxidation coatings on AZ31B magnesium alloy

ارائه دهنده: Provider: Abdelhameed Fardosi

اساتید راهنما: Supervisors: Dr. Arash Fattah-alhosseini

اساتید مشاور: Advisory Professors: دکتر مینو کارباسی- دکتر راضیه چهار محالی

اساتید ممتحن یا داور: Examining professors or referees: Dr. Omid Imantalab - Dr. Masoud Atapour - Dr. Ahmad Keyvani

زمان و تاریخ ارائه: Time and date of presentation: 2026

مکان ارائه: Place of presentation: سالن سیمنار

چکیده: Abstract: This thesis investigates the simultaneous enhancement of corrosion resistance and photocatalytic activity of plasma electrolytic oxidation (PEO) coatings on AZ31B magnesium alloy through the incorporation of strontium (Sr) and chromium (Cr) into the electrolyte. PEO coatings were fabricated using a phosphate-based electrolyte (5 g/L Na3PO4 + 3 g/L KOH) with and without the addition of 0.5 g/L Sr(NO3)2 or Cr(NO3)3, at two current densities of 6 A/dm² and 12 A/dm2. The microstructure, phase composition, surface wettability, roughness, electrochemical corrosion behavior, and photocatalytic activity of the coatings were systematically characterized. The results demonstrated that coatings formed at higher current density (12 A/dm2) exhibited greater thickness compared to those at 6 A/dm². Regarding corrosion resistance, the Sr-modified coating fabricated at 12 A/dm2 showed superior performance with the lowest corrosion current density (3 × 10⁻⁹A/cm²), highest polarization resistance (1480 kΩ.cm2), and largest contact angle (115.1°), indicating hydrophobic surface behavior. The Cr-modified coating fabricated at 12 A/dm2 also exhibited improved corrosion resistance compared to the uncoated substrate, with a corrosion current density of 82 × 10⁻⁹ A/cm2 and a polarization resistance of 162.8 kΩ·cm². Photodegradation tests of methylene blue under visible light revealed that the Cr-modified coating possessed the highest photocatalytic efficiency, followed by the unmodified coating, while the Sr-modified coating showed the lowest activity due to its hydrophobic surface limiting solid–liquid contact. These findings present a strategy for developing multifunctional PEO coatings with tailored properties for applications requiring both corrosion resistance and photocatalytic activity, where Sr doping is optimal for corrosion protection and Cr doping for photocatalytic degradation.