Thin Stable Calcium Phosphatc Coating on Titanium by a Discharging Method in an Electrolyte of Phosphoric Acid and Citric Acid Solution

Abstract

The purpose of this study was to coat thin stable calcium phosphates on titanium substrates using a discharging method in an electrolyte. A titanium plate was connected to the cathode with a platinum anode in phosphoric acid and citric acid solution with oversaturated tri-calcium phosphate powder using a pulsed battery and was treated under discharging. The surface of titanium plates was coated by a calcium phosphate layer with treatment. The surface and the sectioned surface of the coated titanium plates were observed by SEM.
The coated layer was also analyzed by EDX, X-ray diffractory (XRD) analysis, and IR analysis. SEM observation on the sectioned surface revealed that the coated layer with a thickness of 5-10 μm adhered to the mother metal tightly. The results indicated that the composition of the coated layer was hydroxyapatite when the electrolyte contained 2 wt% phosphoric acid with citric acid. On the other hand, that of the coated layer was β-TCP when the electrolyte contained 4 wt% phosphoric acid with citric acid.
Therefore, thin stable calcium phosphate coating without secondary components on titanium could be obtained by discharging in an electrolyte when adjusting the composition and content of the electrolyte.