The detailed corrosion performance of bioresorbable Mg-0.8Ca alloy in physiological solutions

The electrochemical behaviour of biodegradable magnesium alloy Mg-0.8Ca was evaluated in a mammalian cell culture medium (MEM) and NaCl solutions (0.9 wt.%, 0.3 wt.%) using traditional (EIS, PDP, OCP) and local scanning electrochemical (SVET, SIET with pH-selective microelectrode) methods at the micro- and meso-level. Corrosion rates of samples in two different media were determined using weight loss tests. The influence of testing media components, alloy composition and microstructure on the material's degradation process was determined. The SVET/SIET test parameters were optimized for in vitro investigation of the bioresorbable material surface. The mechanism of the alloy's bioresorption was suggested. The effect of microsized phases on the corrosion behaviour of the alloy was proved using complementary in situ monitoring and SKPFM measurements. The rapid degradation rate of the alloy is related to the presence of local microgalvanic cells formed by cathodic alpha-magnesium matrix and anodic Mg2Ca phase. The highest corrosion activity was revealed in the first 12 min of sample exposure to MEM, followed by stabilization of corrosion process due to the material's passivation. Using SEM-EDX analysis, micro-Raman spectroscopy and XPS analysis the composition of the corrosion products was determined. Degradation in MEM proceeds with a formation of magnesium-and-carbonate substituted hydroxyapatite-containing film on the sample's surface. The low possibility of application of Mg-0.8Ca alloy without coating protection in implant surgery was highlighted. (C) 2022 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd.

Automated summary

The electrochemical behavior of biodegradable magnesium alloy Mg-0.8Ca was evaluated using traditional and local scanning electrochemical methods. The corrosion rates and degradation process of the alloy were determined and the mechanism of bioresorption was proposed. The influence of alloy composition and microstructure on corrosion behavior and the composition of corrosion products were investigated. The study also highlighted the low applicability of uncoated Mg-0.8Ca alloy in implant surgery.