Electrocrystallization of Hydroxyapatite and Its Dependence on Solution Conditions

Abstract

Electrocrystallization of hydroxyapatite (HAp) on titanium was achieved by cathodic polarization in solution containing calcium nitrate and ammonium dihydrogen phosphate. The composition and pH of the bath were found to significantly affect the nature and surface morphology of the deposit. The effect of bath temperature was also studied. X-ray diffraction tests and microscopic inspections confirmed the formation of well-crystallized HAp at pH 0 ) 6.0 at any temperature between 70 and 95 °C, whereas, at pH 0 ) 4.2, less-crystallized, thicker, and more porous coatings that contained traces of octacalcium phosphate were observed. The influence of potassium chloride and sodium nitrite on the composition and surface morphology of the deposit was also evaluated. A speciation-precipitation model was applied to better understand the effect of bath conditions. The standard enthalpy of activation was ∼40 kJ mol -1 , indicating that the reaction kinetics is controlled by the interfacial area. The corrosion resistance of the coatings was determined by open-circuit potential and cyclic potentiodynamic polarization measurements in a simulated body fluid. The samples coated at pH 0 ) 6.0 exhibited nobler behavior. The ability to modify the chemistry and surface morphology of the coating by fine control of bath composition, pH, and temperature makes electrochemical deposition a versatile process for deposition of coatings on implants, with a tailored body response.

Elaboration of Monophasic and Biphasic Calcium Phosphate Coatings on Ti6Al4V Substrate by Pulsed Electrodeposition Current

“…[29] In pulsed electrodeposition current associated with H 2 O 2 , the craters and holes disappear (Fig. 5b) and the needles agglomerate.…”

Effect of trisodium citrate on electrolytic deposition of hydroxyapatite coatings

“…The SI HA , SI OCP , and SI DCPD in the experimental conditions of this work were calculated with a popular computer program PHREEQC (Parkhurst and Appelo, 1999). 19,20 Figure 6 clearly shows the influence of pH value on the SIs with respect to HA, OCP, and DCPD. According to this figure, DCPD has SI < 0 over the whole pH range and is therefore not expected to be present in the deposit.…”

The impedance‐titrator : A novel setup to perform automated pH‐dependent electrochemical experiments

“…This deposition can be either irreversible, for example when a hydroxide precipitate converts into an oxide or can be sufficiently protective from the over all amount of material deposited. Elias and Srithar studied the electrocrystallisation of hydroxyapatite on titanium as a function of the solution pH [4]. Other researchers namely Schiller and Epple demonstrated that pH fillers are useful additives [5].…”