Abstract
Abstract
Mechanical polishing can significantly improve the surface integrity of Mg alloys to reduce the corrosion rate (CR) by minimizing the galvanic corrosion sites. In this study, an emery-polishing attachment on a lathe machine has been used for surface polishing of as-turned cylindrical ZM21 Mg alloy. Using Taguchi’s L9 orthogonal array, three process variables with three levels were investigated and optimized for minimum surface roughness (Ra and Rz values) of Mg-alloy samples. The minimum surface roughness values of Ra; 195 nm and Rz; 1481 nm were obtained corresponding to emery paper (EP) grade; 2000, rotational speed; 250 rpm, and polishing time; 2 min. An in-vitro immersion study was conducted in simulated body fluid (SBF) for up to 28 days to investigate the degradation behavior of as-turned and as-polished Mg alloy samples. In-vitro study showed that the as-turned samples (surface roughness; Ra: 640 nm, Rz: 4640 nm) had a higher degradation rate (CR: 3.9 mm year−1 after 28 days) with a higher volume of H2 evolution rate, whereas the polished sample with the minimum surface roughness (Ra: 195 nm, Rz: 1481 nm) exhibited lower weight loss, H2 release rate, degradation rate (CR: 0.95 mm year−1 after 28 days) and minimum loss of mechanical strength. Based on the present study, polishing is recommended as a secondary operation after machining of Mg alloy to reduce the corrosion rate for biodegradable implant applications.