Stability of passive film and antibacterial durability of Cu-bearing L605 alloy in simulated physiological solutions

In this work, the stability of passive film for long-time immersed Cu-bearing L605 (L605-Cu) alloy in the phosphate buffer solution (PBS) was studied by potentiodynamic polarization and electrochemical impedance spectroscopy. The results showed that the impedance of passive film for L605-Cu alloy experienced an initial increase and subsequent stabilization with the increase in the immersion time. In addition, the plate count method was employed to assess the antibacterial durability of L605-Cu alloy against Escherichia coli after long-time immersion. The results indicated that the antibacterial rate of L605-Cu alloy presented a declining tendency with the immersion time prolonging. X-ray photoelectron spectroscopy (XPS) was used to analyze the change of the chemical composition in the passive film on L605-Cu alloy immersed in the PBS for different time. The results showed that Cu content and its compounds in the passive film gradually increased with the immersion time prolonging, hinting declined activity of Cu ions penetrating into the passive film, which resulted in a decrease in the antibacterial performance.