Effect of electrodeposition parameters and substrate on morphology of Si-HA coating

In this study, a Si-HA coating was deposited on Mg-5Zn-0.3Ca alloy substrate by pulse electrodeposition. The effect of varying electrodeposition parameters like current density (20, 40, 60 mA/Cm-2), duty cycle (0.1, 0.2), pH (4, 5, 6) and temperature (25, 85, 100 degrees C) on the composition and morphology of coating were investigated. A homogenous nano-needle morphology of Si-HA coating was chosen as optimum coating. Regarding to results obtain from SEM and XRD, in low current density of 20 mA/cm(-2 )a coarse and non-uniform coating was deposited and in high current density of 60 mA/cm(2), high amounts of hydrogen gas at interface was produced and a non-uniform coating was formatted once more. At middle current density of 40 mA/cm(-2), nano-needle like coating could be deposited. According to results, an increase in duty cycle from 0.1 to 0.2 increased the t(on) and the pH of electrolyte vicinity of cathode and cause calcium phosphate of DCPD deposited along with HA on surface and morphology of coating was also changed from needle like to think plate like. The results also indicated coatings had micro size sheets and agglomerated morphology in 26 degrees C and 100 degrees C, respectively, whereas coating had nano-sized needle- like blades approximately 100-200 nm in length and < 100 nm in thickness in 85 degrees C. the pH less or > 5 for electrolyte (4 and 6) made the plate like morphology for coating. Moreover, the results indicated that the selection of composited Mg alloy with nano-HA as a substrate caused the deposition of Si-HA coatings on it to be more homogenous with better interface in comparison to that of Mg alloy selection as a substrate.