Influence of processing technology on electrochemical corrosion behavior of Ti-6Al-4V alloys

Ti-6Al-4V alloys are typically used for biomedical implants, aerospace components and offshore equipment, where corrosion resistance is critical. In the present paper, the electrochemical corrosion behaviors of Ti-6Al-4V alloys made by different traditional processing and 3D printing technologies in seawater, 3.5 wt.% NaCl, 3.5 wt.% HCl, 5 wt.% HCl and 10 wt.% HCl solutions were studied through polarization curve and electrochemical impedance spectra (EIS) analyses. The influences of microstructure and printing parameters on the corrosion behaviors of Ti-6Al-4V alloys were analyzed. In addition, the corrosion current density, film resistance and charge transfer resistance of traditionally processed Ti-6Al-4V and 3D printed Ti-6Al-4V in the five solutions were compared. The results show that Ti-6Al-4V possesses a better corrosion resistance in seawater than in 3.5 wt.% NaCl, and that the corrosion rate increases with the HCl concentration. Besides, 3D printed Ti-6Al-4V shows a higher corrosion rate in comparison with traditionally processed Ti-6Al-4V because pores are effortless to enrich Cl-. Finally, the ratio of laser power to its scanning speed and the phase constituent composition of the alloy have slight influences on its electrochemical corrosion behavior. It is suggested that for the 3D printed alloy, the deterioration of mechanical properties induced by corrosion damage during servicing should be assessed and considered.