Effect of Technological Parameters on Composition and Structure of Electrodeposited Calcium Phosphate Coatings

The effects, of cation to anion concentration ratio n(Ca)/n(P) in the electrolyte solution, the current density, and the temperature and pH valve of the electrolyte solution on the composition and structure of electrodeposited calcium phosphate coatings were investigated by means of X-ray diffraction, Fourier transformation infrared spectroscopy, and scanning electron microscopy. The results showed that the compositions and structures of the electrodeposited calcium phosphate coatings were highly dependent on the plating parameters. The electrodeposited calcium phosphate coatings deposited at Ca(NO3)2 concentration of 0.042 mol/L, NH4H2PO4 concentration of 0.008 4 ~ 0.042 0 mol/L, pH value of 4.0 ~ 6.0, current density of 0.4 ~ 20.0 mA/cm2, and temperature of 0 ~ 90 deg C consisted of CaHPO4 * 2H2O (DCPD), Ca8H2(PO4)6 * 5H2O (OCP), and Ca10(PO4)6(OH)2 (HA). The thermodynamically unstable DCPD transformed to more stable OCP and HA with increasing temperature, current density, pH value, and n(Ca)/n(P) in the el