Hydroxyapatite coating on titanium by thermal substrate method in aqueous solution

A new hydrocoating method (the thermal substrate method) is proposed for coating calcium phosphates such as hydroxyapatite (HA), on titanium substrates in an aqueous solution. Several factors (e.g., the type of ion source, the heating time and temperature, and the surface roughness of the substrate) affected the characteristics of the precipitate formed by this method. The solution used included 3 mmol dm−3 Ca(H2PO4)2 and 7 mmol dm−3 CaCl2, and its pH was adjusted to 6.5. The experimental studies were conducted under the following conditions: temperature 45–160°C, heating time 10–20 min, and surface roughness of substrate #120–#2000 grid ground using energy paper. A high quality of precipitate, whose predominant component was HA, was obtained on titanium substrates by the thermal substrate method in an aqueous solution. No significant difference in the precipitates was found with the type of ion source. The amount of HA precipitate increased with increasing temperature and with increasing heating time. The features of the precipitate were different, depending on the surface roughtness of the substrate: HA regularly nucleated along the grooves of the rough surface (#120 and #400 grid), and in the case of the fine surface (#1200–#2000 grid), a uniform precipitation occurred. © 2001 Wiley Periodicals, Inc. J Biomed Mater Res 59: 390–397, 2002