Study of the effect of ZnO nanoparticles addition to PEO coatings on pure titanium substrate: Microstructural analysis, antibacterial effect and corrosion behavior of coatings in Ringer's physiological solution

Abstract In this work, a phosphate-based electrolyte, containing ZnO nanoparticles in concentrations of (0, 5, 10, and 15 g/L), was used to achieve coatings on pure titanium by using plasma electrolytic oxidation (PEO) method. Microstructure, phases, and chemical compositions of the coatings were investigated using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) pattern and energy dispersion spectroscopy (EDS), respectively. In order to investigate the corrosion behavior, the samples were dipped in Ringer’s solution, and then potentiodynamic polarization test and electrochemical impedance spectrometry (EIS) were performed. Incorporation of ZnO nanoparticles into the coatings resulted in reduction in the number of pores, and modification of the coating microstructure, which consequently increased corrosion resistance. Also, addition of ZnO nanoparticles resulted in a decrease in the corrosion current density (93% reduction for the sample containing 15 g/L ZnO nanoparticles) in comparison with the uncoated titanium substrate. The results of antibacterial tests revealed that ZnO nanoparticles were able to effectively retain the Gram-positive and Gram-negative bacterial activities, and also, by increasing the concentration of nanoparticles, the intensity of antibacterial effect of the coating was increased.