A nanostructured TiZrNbTaMo high-entropy alloy thin film with exceptional corrosion properties for biomedical application

High-entropy alloys (HEAs) have attracted extensive attention for biomedical application due to their excellent corrosion resistance. In this study, a simple body-center cubic TiZrNbTaMo nanostructured high-entropy alloy thin film (HEATF) was synthesized via magnetron sputtering. Its microstructure, phase structure and corrosion properties were identified by SEM, TEM, electrochemical tests and XPS, respectively. The corrosion properties of this nanostructured TiZrNbTaMo HEATF were studied in phosphate buffer solution at 37 ℃. It was found that the nanocrystals were randomly distributed in the HEATF, and the average grain size was statistically counted to be ∼ 70 nm. This nanostructured TiZrNbTaMo HEATF showed a higher open circuit potential value (−328 mV_SCE), lower corrosion current density (0.017 μA/cm²) as compared with the traditional Ti6Al4V alloy. The cyclic polarization experiments implied that this nanostructured HEATF was not prone to local corrosion. The constant potential polarization demonstrated that the density of the passive film (k = -0.96) formed on the surface the nanostructured TiZrNbTaMo HEATF was better than that of the Ti6Al4V alloy (k = -0.87). Furthermore, the Mott-Schotty analysis showed that the passive film formed on the nanostructured TiZrNbTaMo HEATF exhibited n-type semiconductor. The donor density was smaller than that of the Ti6Al4V alloy at the same film forming potential, verifying that the HEATF’s passive film had higher stability and lower conductivity. The exceptional corrosion properties of this TiZrNbTaMo HEATF were ascribed to the synergistic effects of multiple elements, nanocrystal structure, and a stable surface passive film formation.