The present investigation is laid on nanostructured fluorhydroxyapatite (FHA) coatings (accompanied with 0%, 25% and 60% Fluorine (F - ) substitution into hydroxyapatite(HA) crystalline structure) on AZ91 magnesium based alloy via sol-gel and electrophoretic deposition (EPD) techniques in order to control magnesium degradation rate for bone implant applications. The first step was followed by nanostructured HA coating via sol-gel method. The coated samples were heat treated up to 400?C for further calcination process. Another group of AZ91 samples was anodized by Micro arc oxidation (MAO) method for the initial surface treatment before EPD. FHA powders were prepared using sol-gel method. The powders were heat treated up to 600?C to synthesize high degree of crystalized powders. EPD method was used to apply the FHA powders on AZ91 samples using a (methanol + FHA) suspension bath. Results revealed that the sol-gel technique is just able to create a pure hydroxyapatite coating on AZ91 samples, while EPD is a promising method in fluoridated HA coatings on AZ91 magnesium based alloy specimens. All coated samples had a striking bioactive surface according to simulated body fluid (SBF) immersion test. A considerable degree of decrease (two times and more) in substrate degradation rate has been occurred in all successful coatings. Zeta potential/conductivity measurements revealed that the homogeneity of FHA coatings will decrease as fluorine percentage increase. Electrochemical polarization tests showed a remarkable reduction in corrosion current densities in FHA coated AZ91 samples versus bare AZ91 specimens. Among these, 25% Fluorine substituted in HA crystalline structure (FHA25) coating on AZ91 specimens possesses the best effects on controlling the magnesium degradation rate which is due to the lower solubility of fluoridated HA coatings incorporating higher amount of F - . Keywords : Magnesium, Fluorhydroxyapatite, Bioactivity, Controlling Degradation Rate, Micro Arc Oxidation, Electrophoretic Deposition.
