Abstract
Biodegradable magnesium alloys, such as Mg-Zn-Ca system ones, are promising materials for the manufacture of degradable surgical implants, including screws and plates for osteosynthesis. They possess sufficiently high mechanical properties, controlled degradation rate and excellent biocompatibility. However, high propensity to the local filiform and pitting corrosion jeopardizes the structural integrity of orthopedic implants and, thus, challenges the biomedical application of these alloys. It is generally accepted that non-uniformity of corrosion in Mg alloys is mainly attributed to the enhanced anodic dissolution of Mg matrix neighboring with nobler second phase particles and impurity inclusions, which serve as local cathodic sites. The crystallographic orientation of individual grains can also contribute to nonhomogeneous propagation of corrosion. In the present study, the effect of crystallographic orientation of grains and distribution of second phase / impurity particles on the propagation path of filiform corrosion and location of corrosion pits in the as-cast ZX10 alloy have been investigated using electron backscatter diffraction (EBSD), energy dispersive spectroscopy (EDS) and in-situ video imaging. It is found that filiform corrosion propagates normally to the basal plane of Mg grains, while the particles such as MgO ones causing disruption of the passivation film can produce initiation sites for corrosion pits.
Funding
1. Russian Science Foundation - 23-23-10041