Development of Ternary Hydroxyapatite-Al2O3-TiO2 Nanocomposite Coating on Mg Alloy by Electrophoretic Deposition Method

In the present study, ternary hydroxyapatite (HA)-Al2O3-TiO2 nanocomposite coating and HA nano-coating have been developed on Mg alloy by the electrophoretic deposition (EPD) method for temporary bioimplant application. Following this, a post-heat-treatment has been done at 250 degrees C for 2 h. Detailed microstructural studies indicate uniform deposition of coating with the presence of porosities (area fraction-16%), agglomerated particles of size range 0.3-1.8 mu m and micro-cracks in composite coating. However, in HA-coated samples, the presence of porosities (area fraction-25%) and particles of size range 0.2-1.4 mu m are observed. The phase evaluation shows the presence of HA, Al2O3, TiO2, and Mg phases in the composite coating, whereas presence of HA and Mg phases in HA coating. The residual stress is tensile in nature with a value 88 MPa for composite coating and compressive in nature with a value - 82 MPa for HA coating. The hydrophilicity increases after applying the coating in terms of a decrease in contact angle from 66 degrees for as received Mg alloy to 20-42 degrees, where 42 degrees for HA coating and 20 degrees for composite coating. Corrosion studies reveal that the corrosion potential (Ecorr) of composite coating is marginally shifted toward the negative direction (- 1.3 V(SCE)) as compared to HA coating (- 1.2 V(SCE)). The corrosion rate decreases from 399 mpy for HA coating to 88 mpy for composite coating.

Automated summary

In this study, ternary hydroxyapatite (HA)-Al2O3-TiO2 nanocomposite coating and HA nano-coating were developed on Mg alloy using the electrophoretic deposition (EPD) method for temporary bioimplant application. The microstructural studies showed uniform deposition of the coating with the presence of porosities, agglomerated particles, and micro-cracks in the composite coating. The phase evaluation revealed the presence of different phases in the composite coating and HA coating, and the residual stress varied in nature between the two coatings. The hydrophilicity increased after the application of the coatings, and the corrosion studies showed a decrease in corrosion rate for the composite coating compared to the HA coating.