Microstructure characterization and corrosion behaviour of a nano-hydroxyapatite coating deposited on AZ31 magnesium alloy using radio frequency magnetron sputtering

The present study reports the fabrication of a nano-hydroxyapatite (HA) film on an AZ31 magnesium alloy via radio frequency (RF) magnetron sputtering. The phase composition, microstructure, and surface morphology of the HA coatings were investigated using X-ray diffraction and atomic force microscopy. The polarization tests in a 3.5 wt.% NaCl solution were performed to examine the corrosion behaviour of the HA-coated magnesium alloy. Two HA coating thicknesses of 700 nm and 1500 nm were studied. The coatings homogeneously covered the entire surface of the substrates. In the case of a greater coating thickness, larger crystallites were formed. The potentiodynamic polarization test demonstrated that a 1500-nm thick nanocrystalline HA coating significantly improved the corrosion resistance of the bare AZ31 magnesium alloy.