Effect of exposure time on corrosion behavior of zinc-alloy in simulated body fluid solution: Electrochemical and surface investigation

Zn alloy biocompatible implant materials have wide clinical application but its susceptibility to corrosion in the physiological environment due to increased exposure time is a major constraint. Consequently, diverse electrochemical responses have been investigated to understand the corrosion mechanism at the Zn alloy interface in different immersion times up to 168 h. A self-protective layer of Zn(OH)2 was evidenced over the surface of Zn alloy at higher exposure time in simulated body fluid (SBF) solution. The morphology and chemical composition of the zinc surface has been studied by Field emission scanning electron microscopy (FESEM), X-RAY diffraction (XRD), annulated transmission refraction (ATR), and X-RAY Photoelectron Spectroscopy (XPS). The results indicated that the Zn alloy predominantly forms zinc oxide or hydroxide and zinc phosphate compound as primary corrosion products at the interface which is confirmed from the elemental ratio (Zn/O, Zn/Cl and Zn/P 1:1, 1:2, 2:3 respectively). Additionally, FESEM results confirmed the selective formation of nano structured Zn(OH)2 which is responsible for the protectiveness of zinc specimen at higher exposure period. When Zn alloy was immersed in SBF solution, the corrosion rate was found to be 0.156-0.0976 mmy-1, which proves the sustainability of Zn alloy for biomedical applications and provides an improved degradation mechanism of Zn alloy in SBF solution.