Effect of electropolishing parameters of WE43 magnesium alloy on corrosion resistance of artificial plasma

Abstract

In this study, an improved technique is proposed to obtain bare metal surfaces for implants, stents, and medical devices. The aim is to enhance the corrosion resistance and biocompatibility of the WE43 magnesium alloy by modifying its surface characteristics through electropolishing. This is achieved using an electrolytic mixture with varying concentrations of HNO3 and C2H5NO3. The morphology, microstructure, chemical composition, and phase structures of the coating are analyzed by SEM, XPS, and XRD. The corrosion resistance of the surface was analyzed by polarization and bio-corrosion behavior tests. During the electropolishing process, unstable Mg(NO3)2 is easily formed by Mg and HNO3. However, the addition of C2H5OH helps release C2H5NO3 and HNO3 ions from the electrolyte, leading to the formation of a thin and dense layer of MgO on the alloy surface. The results revealed that surface roughness significantly affected the corrosion resistance of the alloy. Specifically, the oxide layer thickness gradually decreased with increasing voltage during electropolishing. However, it was observed that higher electropolishing voltages (beyond 0.5 V) caused surface cracking and reduced the corrosion resistance of the alloy. Therefore, it is necessary to investigate the optimal electrolytic polishing parameters to enhance the corrosion resistance of WE43 magnesium alloy. According to the experimental results, the optimal electrolytic polishing parameters for WE43 magnesium alloy were determined as follows: 2.0 wt% HNO3 and C2 H5OH, a voltage of 0.45 V, and a time of 300 s. These parameters also exhibited the best biocompatibility characteristics.