In-situ XAFS and SERS study of self-healing of passive film on Ti in Hank's physiological solution

By Wang, Lu; Yu, Hongying; Wang, Shaoyang; Qiao, Lei; Sun, Dongbai
Published in Applied Surface Science 2019

Abstract

The self-healing of passive film on Ti after being damaged in Hank's physiological solution greatly fluctuates with time and its mechanism has been investigated by in-situ X-ray absorption fine structure spectroscopy (XAFS) and surface enhanced Raman spectroscopy (SERS) in a novel electrochemical repassivation set-up. The self-healing response is instant and the current density decays within 50 s due to the increase of the ratio of O and Ti atoms. The increase of the coordination number of TiO contributes to the decrease of current density until 6000 s. Moreover, the in-situ structure evolution is vastly different from that of ex-situ. Two time-dependent adsorbed intermediates exist during self-healing, the adsorption layers of TiOHads and TiOH, and finally the interface forms a stable passive film of OTiOH after 1000 s with good corrosion resistance. Besides, in-situ XAFS and SERS exhibit a high disorder and amorphous nature of passive film on Ti, and the crystallinity increases from 300 s to 6000 s. Additionally, the time-dependent structure evolution and mechanism of self-healing of titanium passive film in local atomic scale will help to understand the corrosion science and protection in healthcare.

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