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The increasing demand for titanium and its alloys used for implants results in the need for innovative surface treatments that may both increase corrosion resistance and biocompatibility and demonstrate antibacterial protection at no cytotoxicity. The purpose of this research was to characterize the effect of two-stage anodization—performed for 30 min in phosphoric acid—in the presence of hydrofluoric acid in the second stage. Scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy, glow discharge optical emission spectroscopy, nanoindentation and nano-scratch tests, potentiodynamic corrosion studies, and water contact angle measurements were performed to characterize microstructure, mechanical, chemical and physical properties. The biologic examinations were carried out to determine the cytotoxicity and antibacterial effects of oxide coatings. The research results demonstrate that two-stage oxidation affects several features and, in particular, improves mechanical and chemical behavior. The processes influencing the formation and properties of the oxide coating are discussed.

This paper presents results of oxidation tests and corrosion investigations of titanium alloy Ti13Nb13Zr performed at different conditions. The oxide layers have been formed by electrochemical method in 2M H3PO4 + 0.3% HF solution for 30 min. and 1 h at 20 V constant voltage. The corrosion tests have been made by potentiodynamic method in Ringer`s solution at pH ranged between 3 and 7. It has been shown that the nanooxide films, which improve corrosion resistance of titanium alloy Ti13Nb13Zr even if acidic environment, have appeared.

The development of composite oxide layers on the Ti13Nb13Zr alloy, their structure and properties, were demonstrated. Two subsequent methods were applied to prepare the composite layers. During the first stage, gas oxidation produced a dense compact oxide layer, and subsequent oxide nanotubes were formed applied an electrochemical oxidation. The scanning electron microscopy, energy-dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, and Raman spectroscopy were used to examine the appearance, thickness, chemical and phase composition of the oxide layers. The results obtained revealed that the composite layers composed of two zones. The electrochemical formation of the outer nanotubular oxide zone occurred if the thickness of the first inner oxide zone was small enough because of resistance increasing with the inner zone thickness followed by a decrease in electrochemical reaction rate. The decreasing corrosion resistance of the Ti13Nb13Zr alloy was observed and explained by a model electric circuit.