Electrochemical depositions of calcium phosphate film on commercial pure titanium and Ti–6Al–4V in two types of electrolyte at room temperature

Electrochemical depositions of calcium phosphate film on commercially pure titanium (cp-Ti) and Ti–6Al–4V in two types of electrolytes, mono-calcium phosphate monohydrate (MCPM) based aqueous solution and supersaturated calcium phosphate solution (SCPS), were carried out by the cathodic polarization. The calcium phosphate coating layer was successfully deposited on cp-Ti and Ti–6Al–4V under 3 mA/cm2 current density for 45 min. The major phases that appeared in the film were DCPD (brushite) co-existed with octa-calcium phosphate (OCP). After soaking in revised simulated-body-fluid (r-SBF), the amorphous bone-like apatite became a single phase within a day for the specimen obtained from MCPM electrolyte. The specimens obtained from SCPS electrolyte took a week to complete the apatite precipitation in r-SBF. From the scratch test, the highest critical load of 87.2 N was obtained from the as-deposited rod-like DCPD on cp-Ti substrate. The critical load was decreasing almost 50% for all of the specimens after apatite precipitation in r-SBF. The decrease of critical load might result from loosening of the film structure during immersion of the specimens in r-SBF. The thickness of the films was 44–55 μm in average, which satisfied the qualification for using as an implant material.