In Vitro Corrosion and Bioactivity of Tungsten Inert Gas-Cladded AZ31-Zn Coatings on Ti-6Al-4V for Biomedical Applications

Abstract

In this study, AZ31 (Mg alloy), Zinc (Zn), and AZ31-Zn preplaced layers were applied on the Ti-6Al-4 V (Ti64) alloy used for biomedical purposes using the tungsten inert gas (TIG) cladding method. Scanning electron microscope (SEM) and energy-dispersive x-ray spectroscopy (EDX) analysis revealed uniform coatings with AZ31-Zn exhibiting lamellar, heterogeneous morphology due to the presence of Mg-Zn intermetallics (Mg12Zn17). X-ray diffraction (XRD) confirmed the presence of alpha-Ti and beta-Ti in the substrate as well as Mg, Zn, and Mg-Zn intermetallic phases in the coatings. Electrochemical tests revealed that AZ31 had a high corrosion rate of 0.349 mm<middle dot>year-1 (Icorr = 1.53 x 10-2 A<middle dot>cm-2), Zn exhibited 0.200 mm<middle dot>year-1 (Icorr = 1.33 x 10-2 A<middle dot>cm-2), while AZ31-Zn showed the lowest corrosion rate of 0.014 mm<middle dot>year-1 (Icorr = 1.06 x 10-3 A<middle dot>cm-2) and the highest polarization resistance (2105 Omega), indicating controlled biodegradation. Contact angle measurements indicated hydrophilic surfaces: 77 degrees for AZ31, 87 degrees for Zn, and 80 degrees for AZ31-Zn, which is favorable for cell adhesion. In vitro SBF immersion demonstrated dense and homogeneous Ca-P deposition on AZ31-Zn, highlighting enhanced bioactivity. These results suggest that the AZ31-Zn coating effectively balances corrosion resistance, biodegradability, and bioactivity, making it a strong candidate for temporary implants and bone stabilization applications. This study demonstrates that TIG cladding can produce multifunctional coatings that optimize both in vitro corrosion sensitivity and bioactivity performance in next-generation biomaterials.