Impact of the Applied Electrode System on Properties of Electrodeposited Calcium Phosphate Coatings

The morphology and physicochemical properties of electrochemically deposited CaP coatings depend on the applied process parameters; however, the influence of different electrode systems has not been studied so far. In this work, the possibility of electrochemical deposition of CaP coatings on Ti6Al7Nb alloy using different electrode systems (two-electrode and three-electrode) and the influence of the electrode system and selected ranges of deposition parameters on the properties of the deposited CaP coatings were investigated. The morphology and physicochemical properties of the CaP coatings were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy, X-ray diffraction (XRD), and corrosion studies. The results confirmed the effective electrodeposition of CaP coatings using both electrode systems. The applied electrode system and deposition parameters cause changes in the morphology of the obtained coatings. Chemical structure analysis confirmed the presence of mainly hydroxyapatite in the deposited CaP coatings. With the change in voltage/potential in a more cathodic direction, in addition to hydroxyapatite, a dicalcium phosphate dihydrate (DCPD) structure appears. The corrosion tests have shown that the applied deposition parameters have an impact on corrosion resistance and the deposited coatings exhibited protective properties against corrosion under physiological conditions. The CaP coatings with optimal properties for biomedical applications were deposited at a voltage of -4 V in the two-electrode system and a potential of -4 VSCE in the three-electrode system.