Electrochemical deposition of hydroxyapatite on titanium substrates in metastable calcium phosphate solution under pulse current

Titanium (Ti) metal substrates were etched in sulfuric acid (H ₂S0₄) with concentrations of 25, 50, 75 and 97% at 60°C for 30 min. Apatite films were deposited onto unetched and etched substrates by an electrodeposition method under a pulse current. The electrolyte was metastable calcium phosphate solution that had 1.5 times the ion concentrations of human body fluid. but did not contain magnesium ion at 36.5C. Deposition times were 90 min. We used the average current density of 0.01 A/cm² and ON time equal to OFF time of 15 s. In the electrodeposition. hydrogen was incorporated into the surface of the Ti substrates to form titanium hydride (TiH₂) on the substrate surfaces. After the electrodeposition, all specimens were heated at 600°C for 60 min. The adhesion between apatite and substrates were greatly improved by the heat treatment for the substrates etched in 50 and 75% H₂SO₄. It is considered that in these specimens the anchoring effect due to the microstructural roughness formed by etching was enhanced by the shrinking of apatite crystals during the heat treatment.