Zn-, Cu- or Ag-incorporated micro-arc coatings on titanium alloys: Properties and behavior in synthetic biological media

Zn-, Cu- or Ag-incorporated calcium phosphate coatings were deposited on pure titanium and Ti-40 wt% Nb substrates by the micro-arc oxidation method. Microstructure, morphology, phase composition, physicochemical and antibacterial properties of the formed coatings and their behavior in synthetic biological media have been studied. Due to the different compositions of the electrolytes and different substrates the MAO process took place at various electro-physical parameters such as current densities and voltages. As a result, the coatings had different properties, phase composition and were characterized by a different behavior in synthetic biological fluids. When using the acidic electrolyte, the applied voltage varied in the range of 200-300 V. In the case of an alkaline electrolyte, the voltage range was 350-450 V. The current density of the MAO process in acidic electrolyte was ten times higher than that in alkaline electrolyte. Therefore, the thickness, roughness and porosity of the Zn-, Cu-incorporated calcium phosphate coatings deposited in acidic electrolyte were the highest. The Zn-, Cu-incorporated coatings showed weight gain in the biological fluids due to intensive dissolution and consequent sedimentation of the calcium phosphates on the coating surface. Ag-incorporated coatings dissolved slowly in the biological fluid. The calcium phosphate coatings containing trace elements Zn, Cu or Ag demonstrated antimicrobial activity against Staphylococcus aureus 209P and in general, did not show cytotoxic effect on myelocariocytes.