Electrochemical Surface Nanostructuring of Ti47Cu38Fe2.5Zr7.5Sn2Si1Ag2 Metallic Glass for Improved Pitting Corrosion Resistance

Abstract

Ti‐based bulk metallic glasses are envisioned for human implant applications. Yet, while their elevated Cu content is essential for a high glass‐forming ability, it poses biocompatibility issues, necessitating a reduction in near‐surface regions. To address this, surface treatments that simultaneously generate protective and bioactive states, based on nanostructured Ti and Zr‐oxide layers are proposed. An electrochemical pseudo‐dealloying process using the bulk glass‐forming Ti47Cu38Fe2.5Zr7.5Sn2Si1Ag2 alloy is defined. Melt‐spun ribbons are immersed in hot concentrated nitric acid solution, monitoring the anodic polarization behavior. From the current density transient measurements, together with surface studies (field‐emission scanning electron microscopy, transmission electron microscopy, and Auger electron spectroscopy), the surface reactions are described. This nanostructuring process is divided into three stages: passivation, Cu dissolution, and slow oxide growth, leading to homogenous nanoporous and ligament structures. By tuning the applied potential, the pore and ligament sizes, and thickness values are adjusted. According to X‐ray photoelectron spectroscopy, these nanoporous structures are Ti and Zr‐oxides rich in hydrous and nonhydrous states. In a simulated physiological solution, for those treated glassy alloy samples, complete suppression of chloride‐induced pitting corrosion in the anodic regime of water stability is achieved. This high corrosion resistance is similar to that of clinically used cp‐Ti.