Zinc/Silver particle (Zn/AgP) composite coatings: Evaluation of corrosion in physiological environments and antibacterial activity against P. aeruginosa

In this work, zinc/silver particle (Zn/AgP) composite coatings were manufactured by electrodeposition to investigate their antibacterial capacity and corrosion rate in physiological environments. The morphology and composition of the coatings were analysed by glow-discharge optical emission spectroscopy and scanning electron microscopy coupled to an energy dispersive spectrometer. The results showed the formation of Zn/AgP composite coatings with a homogeneous distribution of Ag throughout the coating surface and depth. Additionally, the Ag content in the coatings increased with increasing concentrations of AgP in the electrolytic solution. The Zn/AgP composite coatings with 0.30 wt. % Ag on the surface (0.30 wt. % Ag_surf) showed efficiencies close to 100% growth inhibition of the bacteria Pseudomonas aeruginosa after 10 min of contact. The corrosion rate of the Zn and the Zn/AgP (0.30 wt. % Agsurf) coatings in Hank's, Ringer's and Phosphate buffered saline (PBS) solutions was evaluated by polarization curves and by immersion tests over different time periods (7, 30, and 40 days). The corrosion rate of the Zn/AgP (0.30 wt. % Agsurf) coatings was on the order of tenths of microns per year and the amount of zinc mass dissolving per day was in the range of 0.15 to 0.7 mg cm^-2. Additionally, the surface of the coatings was analysed by X-ray diffraction (XRD) after 40 days of immersion. These results showed the formation of ZnO, as the main corrosion product, in the samples immersed in Hank's and Ringer's solutions. In the samples immersed in PBS, the formation of a passivating film of Zn₂(PO₄)₃•2H₂O was detected.