Comparative Study of Strontium- and Chromium-Modified PEO Coatings on Mg Alloys for Photocatalytic Degradation of Methylene Blue

Fardosi A., Fattah-Alhosseini A., Karbasi M., Chaharmahali R., DİKİCİ B., Kaseem M.

Journal of Ultrafine Grained and Nanostructured Materials, vol.59, no.1, pp.41-48, 2026 (Scopus)

  • Publication Type: Article / Article
  • Volume: 59 Issue: 1
  • Publication Date: 2026
  • Doi Number: 10.22059/jufgnsm.2026.01.04
  • Journal Name: Journal of Ultrafine Grained and Nanostructured Materials
  • Journal Indexes: Scopus, Applied Science & Technology Source, Directory of Open Access Journals
  • Page Numbers: pp.41-48
  • Keywords: AZ31B Mg alloy, Methylene blue, Photocatalytic, Plasma electrolytic oxidation (PEO)
  • Ataturk University Affiliated: Yes

Abstract

In this study, plasma electrolytic oxidation (PEO) coatings were developed on AZ31B Mg alloy under a constant current density of 12 A·dm-2 in a phosphate-based electrolyte, with modifications introduced by strontium (Sr) and chromium (Cr) ions. Three coating types were obtained: unmodified (12A), Sr-modified (12A-Sr), and Cr-modified (12A-Cr). All coatings exhibited porous and micro-cracked morphologies, characteristic of oxide ejection and rapid solidification during the PEO process. Grazing-angle X-ray diffraction (GXRD) confirmed the presence of MgO and ZnAl2O4 phases. Surface characterization revealed that the 12A-Sr coating displayed pronounced hydrophobicity (contact angle ≈115°), attributed to chemical and microstructural modifications that enhanced air entrapment. Photocatalytic experiments demonstrated that all coatings were active under visible light, with the Cr-modified coating showing the highest MB degradation efficiency, followed by the unmodified and Sr-modified samples. Electrochemical impedance spectroscopy (EIS) further indicated that visible light irradiation significantly improved charge transfer, as evidenced by reduced Nyquist arc radii, highlighting efficient electron–hole separation and accelerated interfacial reactions. The results demonstrate that Sr- and Cr-modified PEO coatings hold promise for improving photocatalytic wastewater treatment.