Surface modification of titanium utilizing a repassivation reaction in aqueous solutions

The surface modification of titanium utilizing repassivation reaction was attempted. The original surface oxide film on titanium plates were mechanically removed under immersion in water and Hanks' solutions with pH 5.0 and 7.4 followed by repassivation or regeneration of surface oxide film in the same solutions. Then the surface-modified titanium plates were immersed in Hanks' solution (pH 7.4) up to 604.8 ks. Their surface was analyzed with scanning electron microscopy with energy dispesive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffractometry, and the mass gain was measured using a microbalance, to confirm the performance of the modification. It was found that more calcium phosphate was precipitated on specimens modified in Hanks' solutions in comparison with that in water. Calcium and phosphate ions contained in the surface oxides modified in Hanks' solutions had effect for the titanium surface to adsorb more calcium and phosphate ions than specimens repassivated in water. In addition, more calcium phosphate was precipitated on titanium modified in pH 5.0 solution than that in pH 7.4 solution because more H2PO4- and/or HPO42- ions exist in the surface oxide regenerated in pH 5.0 Hanks' solution than in pH 7.4 Hanks' solution. It is suggested that a solution with proper pH and ion concentration for the modification should give higher efficiency for the modification of titanium surface.