Title: Effect of Na₂SiF₆ concentration on the plasma electrolytic oxidation of AZ31B magnesium alloy

Authors: Zeeshan Ur Rehman; Byung Hyun Ahn; Jung Il Song; Bon Heun Koo

Addresses: School of Materials Science and Engineering, Changwon National University, Changwon 641-773, Korea ' School of Materials Science and Engineering, Changwon National University, Changwon 641-773, Korea ' Department of Mechanical Engineering, Changwon National University, Changwon 641-773, Korea ' School of Materials Science and Engineering, Changwon National University, Changwon 641-773, Korea

Abstract: The effect of Na₂SiF₆ on the composition, morphology and mechanical properties of plasma electrolytic oxidation (PEO) coatings produced on AZ31B magnesium alloy was investigated. It was explored that the addition of Na₂SiF₆ into the Na₂SiO₃-NaOH electrolyte solution substantially enhances the surface quality of the PEO coating by eliminating the amorphous residuals and decreasing the surface porosity. Furthermore, the average coating thickness was significantly increased by increasing the Na₂SiF₆ concentration up to 0.5 g/l with the highest value of coating thickness being 85.31 µm. In addition, hardness was remarkably enhanced, by increasing the concentration of Na₂SiF₆ up to 0.5 g/l. The X-ray diffractometer (XRD) results revealed that the intensity of MgF₂ peaks increases with Na₂SiF₆ concentration. Major phases detected in the XRD pattern were MgO (periclase), Mg₂SiO₄ (forsterite) and MgF₂. Finally, it was revealed from the wear analysis that the anti-wear resistance of the coatings was significantly improved with Na₂SiF₆ concentration.

Keywords: AZ31B magnesium alloys; plasma electrolytic oxidation; PEO coatings; fluoride ion; scanning electron microscopy; SEM; sodium fluorosilicate; Na2SiF6; amorphous residuals; surface porosity; coating thickness; wear resistance.

DOI: 10.1504/IJSURFSE.2016.079043

International Journal of Surface Science and Engineering, 2016 Vol.10 No.5, pp.456 - 467

Received: 20 May 2015
Accepted: 07 Sep 2015
Published online: 10 Sep 2016 *

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