Nano-to-micron scale surface topography dictates corrosion behavior of biodegradable LiZn4-based intermetallic

Despite being a critical design parameter, how surface roughness governs the corrosion of LiZn4-based intermetallic (LiZn4-IMC), a newly developed biodegradable material, remains completely unexplored. In this study, LiZn4-IMC is fabricated into two distinct surface roughness scales, nano (Ra = 58 nm) and micron (Ra = 1333 nm), and immersed in 0.9% NaCl solution for 30 days. The micron sample exhibits a 40% faster corrosion rate and an 80% poorer corrosion uniformity. This phenomenon primarily originates from three factors. Firstly, the micron sample possesses about 8% larger surface area. Secondly, the valleys within the grooves of the micron sample act as anodes, while the ridges as cathodes, forming galvanic couples that accelerate pitting corrosion. Lastly, the corrosion products on the micron sample contain higher amounts of nano-columnar ZnO with relatively poor protective properties and show a groove-like morphology, which fails to effectively protect the substrate.