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

Abstract

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.

In Vivo Corrosion Behavior of Biodegradable Magnesium Alloy by MAF Treatment

“…Materials with bacterial resistance are highly desirable in medical implantation procedures [8,39]. Scanning electron microscopy observation of the MAF coating in this experiment reveals similarities between the fluorinated coating and the previous study [15][16][17]. Therefore, we compared the results of the in vivo corrosion with the Hank's Balanced Salt Solution (HBSS) immersion experiments from previous studies.…”

“…The corrosion tests in the in vivo environment were performed in combination with existing in vitro experiments on the MAF coating treatment. The composition, surface morphology, and electrochemistry of MAF-coated magnesium alloys have been evaluated to some extent by in vitro experiments in previous studies, with more satisfactory results [15][16][17]. In this experiment, the processed AZ31 samples were processed at 190 V constant voltage mode.…”

“…Based on the above facts, it can be stated that the coating on the magnesium substrate is prepared completely and that the coating has a certain corrosion limitation. However, the corrosion resistance of MAF-treated coatings in the in vivo environment has not been studied previously [15][16][17]. In a study by Chan [31], the need for loss analysis of implantable materials, especially magnesium alloys, is raised.…”

“…Experiments have been carried out to prepare MgF 2 coatings using the microarc fluorination (MAF) method [15][16][17]. A series of in vitro corrosion tests proved that the microarc fluoride treated magnesium alloy, compared to the untreated ones, has been significantly improved in anticorrosion properties.…”

“…This method is based on the principle of electrolysis. MgF 2 layers are prepared on magnesium or magnesium alloy substrates using a certain voltage as a reaction condition in a fluorinated solution [17,18]. The MAF method was followed in this experiment.…”