Hydroxyapatite (HA) coating was deposited on commercially pure Ti to improve its biocompatibility as a biomedical implant material. The HA layer was deposited by the electrophoretic deposition (EPD) method. The processing parameters controlled the HA structure. In this research, the applied voltage was varied 20, 30, and 40 V to optimize a free-crack layer. The current output during EPD at 20 V was in the order of 10-5 A/cm2. A higher current density in the order of 10-4 A/cm2 was obtained at 30 and 40 V. The coating formed at 20 V was relatively free of crack. A high number of cracks began to observe in the layer formed at 30 V, while only a few cracks were revealed on the layer formed at 40 V. The average thickness of the HA layer increased slightly with applied voltage. The thickness was approximately 40±5 µm, as observed by an optical microscope. The optimum voltage to produce a thick HA layer with a small number of cracks was at 40 V.

Bioactive hydroxyapatite (HA) coating is applied on a commercially pure Ti by electrophoretic deposition (EPD). Optimizing the coating structure is necessary to obtain a stable layer and the best corrosion protection. The EPD was conducted at a constant voltage of 20, 30, and 40 V for 30 min in a HA/DMF (dimethylformamide) suspension. Uniform HA layers with a Ca/P ratio of 1.82 were successfully deposited on the Ti surface. The layers, which consisted of HA grains with the size of 1-5 μm, exhibited a gradual increase in thickness of 32, 50, and 60 μm with formation voltage. For the biomedical application, the suitable coating thickness was at least 50 μm. The high compaction of HA grains deposited at 30 V led to an order magnitude higher polarization resistance and ten times lower corrosion current density relative to the other specimens. The porous HA layer formed at 20 V, and the presence of cracks in the 40 V-coating led to a lower corrosion resistance relative to the 30-V coating. The 20 V- and 30 V-coatings remained intact and triggered the deposition of HA during immersion in simulated body fluid for 28 days, while the 40 V-coating dissolved into the solution. The optimum EPD voltage for depositing a stable HA coating with reasonable coating thickness and the best corrosion resistance was 30 V.