Corrosion and biocompatibility examination of multi-element modified calcium phosphate bioceramic layers

Multi-ions doped bioactive calcium phosphate (dCaP) layers were developed by pulse current deposition onto surgical grade titanium alloy material (Ti6Al4V). The coatings were electrodeposited from base electrolyte containing adequate amounts of calcium nitrate and ammonium dihydrogen phosphate at 70 °C. After electrodeposition, the pure CaP layers were doped with different ions that possess bioactive and antimicrobial properties, such as Zn²⁺, Mg²⁺, Sr²⁺ and Ag⁺ ions. The morphology and structure of coatings were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy-dispersive X-ray Spectroscopy (EDX) as well as XRD and FT-IR measurements. The results revealed the pulse current deposited and surface post-treated CaP layer to be mainly in hydroxyapatite phase. The corrosion properties of bioceramic coatings were assessed in conventional simulated body fluid (SBF) in a three electrode open cell by using potentiodynamic polarization measurements over two weeks period. The electrochemical results revealed that the pure calcium phosphate (CaP) coated implant material and the bare implant possess the highest resistivity to corrosion, while the modified calcium phosphate coating showed lower corrosion resistance by at least one order of magnitude. The cell viability measurements showed that the electrochemically deposited CaP layer was biocompatible.