Enhanced corrosion resistance of biodegradable Mg alloys via ultrasonically treated fluoride coating

Magnesium (Mg) and its alloys are promising materials for use in medical applications due to their good mechanical properties, biocompatibility, and biodegradability. However, the rapid corrosion of Mg alloys restricts their range of use in these applications. Fluoride conversion (HF) coating is one of the most effective and environmentally friendly surface modifications available to address this limitation. The formation of a thin, uniform, smooth, and adherent fluoride coating improves the corrosion and wear resistance of Mg alloys. However, this method is not suitable for long-term medical treatment. In previous research, we found that ultrasonically treated fluoride (HFU) coatings can increase the corrosion resistance of Mg alloys. The aim of this study, therefore, was to investigate in more detail the surface morphology, coating thickness, composition, and corrosion of ultrasonically treated fluoride-coated Mg alloys. The results indicated that the HF and HFU coatings were identical in terms of thickness and composition. However, unlike the HF-coated specimens, there were no pores and cracks on the surface of the HFU-coated specimens, which also exhibited significantly higher corrosion resistance in electrochemical corrosion and mass loss tests. As a result, HFU- coated Mg alloys may prove suitable for use in long-term medical treatment.