Composition of corrosion layers on a magnesium rare-earth alloy in simulated body fluids.

In this study, the composition of corrosion product layers on a magnesium rare-earth alloy in simulated body fluid (m-SBF) containing albumin in physiological concentration is examined. The time dependence of the composition of the layer is studied. The ions from the body fluid that participate in the corrosion layer formation were identified by analyzing layers formed in different solutions that contain only some of the ions of SBF. The layer composition was analyzed by different complementary methods. We used energy dispersive X-ray analysis, grazing incidence X-ray diffraction, and Fourier transform infrared spectroscopy. The morphology of the corrosion layers was studied using scanning electron microscopy and light microscopy. In m-SBF with and without albumin we found an amorphous layer of carbonated calcium phosphate with some calcium replaced by magnesium. It can be clearly shown that calcium is only deposited in the corrosion layer if phosphates are in the solution. The cross-sections reveal that there are some sharp crevices in the substrate. The work systematically explores the nature of surface layers on magnesium rare-earth alloys formed in complex SBFs, with the aim to elucidate the influence of specific electrolyte components on the morphology, structure, and composition of corrosion layers on Mg alloys.