The formation mechanism and bio-corrosion properties of Ag/HA composite conversion coating on the extruded Mg-2Zn-1Mn-0.5Ca alloy for bone implant application

In this study, a silver and hydroxyapatite (Ag/HA) composite coating was generated on an extruded Mg-2ZnlMn-0.5Ca magnesium alloy through a chemical conversion process. Scanning electron microscopy (SEM) observation showed that a gray conversion coating was formed with white snow -like and gray globular particles or crystals located randomly above the coating. X-ray diffraction (XRD) combined with X-ray photoelectron spectroscopy (XPS) analysis indicated that the conversion coating was mainly composed of Caio(PO4)6(OH)(2) with limited quantities of Ag/Ag2CO3, CaHPO4.2H(2)0 and CaSiO3. The formation mechanism of the Ag/HA composite conversion coating is discussed in thiswork. The electrochemical polarization and EIS tests showed that the conversion coating markedly improved the bio-corrosion resistance of the Mg-2Zn-lMn-0.5Ca alloy in Hank's solution. Adhesion test showed that the coating has a strong bonding strength. The bactericidal activity was assessed with the zone of inhibition method, and the composite coating on the Mg alloy substrates exhibits good antibacterial performance(C)2017 Elsevier B.V. All rights reserved.