Comparison of the wettability and corrosion resistance of two biomedical Ti alloys free of toxic elements with those of the commercial ASTM F136 (Ti–6Al–4V) alloy

Abstract

Titanium alloys have been widely used as biomaterials. However, contact of titanium with body fluids can release toxic ions due to degradation. The present work aimed to compare the wettability and corrosion resistance of two Ti alloys without toxic ions, Ti–30Nb–7Zr (TNZ) and Ti–47Nb (TN), with those of the commercial biomedical alloy Ti–6Al–4V-ELI (ASTM F136). Corrosion studies were carried out in a three-electrode cell conventional system, which Ti alloys as working electrodes were exposed to 0.9% sodium chloride electrolyte at 37 °C to determine if they have surface properties adequate for biomedical applications. α and β phases present on the microstructure were distinguished using scanning electron microscopy (SEM). Chemical surface composition was performed using X-ray photoelectron spectroscopy (XPS) analysis. Surface energy was determined by wettability testing. For TN and TNZ alloys the microstructure consisted of a β matrix, although only TNZ exhibited α precipitates. In contrast, F136 alloy microstructure presents α matrix, which was strengthened by the β phase. All alloys tested exhibited an increase in corrosion potential with the immersion time, indicating the growth and stabilization of the passive oxide film. The results showed that ASTM F136 is more hydrophilic but less corrosion resistant than the TN and TNZ alloys. It remains to be seen in practical applications whether the lower hydrophobicity of TN and TNZ alloys is compensated by lower toxicity and higher corrosion resistance.