Electrodeposition of calcium phosphate coatings on titanium alloy implant at different Ca/P ratios and different times

Brushite (CaHPO.2HO) was coated on titanium alloy substrate by electrochemical deposition technique. Then, it was converted to hydroxyapatite [Ca (PO) (OH) ] by NaOH treatment. Different Ca/P ratios (0.335, 0.67, 1.0, 1.667) were applied. The surface morphology, chemical composition and phase identification of the coatings were investigated. The results showed that the coating layer is brushite except at 5 hr coating time. Furthermore, Ca/P ratio has insignificant effect on coating thickness and weight gain. However, with increasing coating time, coating thickness and weight gain are increased. Coating thickness at Ca/P ratio of 1.67 and coating time of 1 hr at 1.5 mA/cm² was about 17 and 23 μm with and without treatment, respectively. It increased to about 28 and 48 μm at 5 hr coating time, with and without NaOH treatment, respectively. The formed phase is changed with increasing coating time to 5 hr and no hydroxyapatite was directly electrocrystallised.

Keywords: in situ synthesis, biomaterials, coatings, electrodeposition, calcium phosphate, brushite, hydroxyapatite, titanium alloys, electrocrystallisation, titanium alloy implants