Microstructure and Corrosion of Cast Magnesium Alloy ZK60 in NaCl Solution

Abstract

In this work, the effects of the microstructure and phase constitution of cast magnesium alloy ZK60 (Mg-5.8Zn-0.57Zr, element concentration in wt.%) on the corrosion behavior in aqueous NaCl (0.1 mol dm−3) were investigated by weight-loss measurements, hydrogen evolution tests, and electrochemical techniques. The alloy was found to be composed of α-Mg matrix, with large second-phase particles of MgZn2 deposited along grain boundaries and a Zr-rich region in the central area of the grains. The large second-phase particles and the Zr-rich regions were more stable than the Mg matrix, resulting in a strong micro-galvanic effect. A filiform corrosion was found. It originated from the second-phase particles in the grain boundary regions in the early corrosion period. The filaments gradually occupied most areas of the alloy surface, and the general corrosion rate decreased significantly. Corrosion pits were developed under filaments. The pit growth rate decreased over time; however, it was about eight times larger than the general corrosion rate. A schematic model is presented to illustrate the corrosion mechanism.

On the Corrosion Fatigue of Magnesium Alloys Aimed at Biomedical Applications: New Insights from the Influence of Testing Frequency and Surface Modification of the Alloy ZK60

“…It is unclear whether the locations of individual pits are completely random or are pre-determined by the microstructural/chemical inhomogeneity. However, the results of Li et al [87] show, quite unambiguously, that in line with the discussion given in the introduction, the micro-galvanic corrosion in the alloy ZK60 initiates primarily in the areas around the second-phase particles at the grain boundaries. Figure 8 indicates that once initiated, the corrosive pits tend to grow and deepen under the action of cyclic loads.…”

Toward understanding in vivo corrosion: Influence of interfacial hydrogen gas build‐up on degradation of magnesium alloy implants

“…Furthermore, the values compare well with corrosion rates reported in the literature for MgZnZr alloys of similar composition, such as the 0.32–1.03 mm yr −1 in Hanks' solution; 1.27–1.37 mm yr −1 in PBS and 1.5–3.5 mm yr −1 in 0.1 M NaCl. This provides a good quantifying of the reliability of the setup and material used 36–39 …”

“…This provides a good quantifying of the reliability of the setup and material used. [36][37][38][39] Upon the introduction of agarose films into the setup, the corrosion rates of the Mg-Zn-Zr samples at first increased with a value of 9.95 mm yr À1 being recorded for the thinnest layer (x = 0.3 mm).…”

Effect and mechanism of a novel Mg-Nd-Gd-Sr alloy on osteogenic differentiation of bone marrow mesenchymal stem cells

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