Introduction. Plasma electrolytic oxidation of pure Mg could provide the formation of low dissolution porous oxide coating in silicate-based baths. Corrosion resistance is the main characteristic of obtained coatings for Mg-based implants. There are several methods for corrosion rate measurements as weight loss, volume loss, hydrogen evolution, visual and electrochemical methods. Though these methods often give different rates. The imitation in-vivo conditions in the in-vitro tests have difficulties before analyzing the corrosion behavior of a degradable material. This is connected with corrosion behavior influenced by different environments. 

Aim: The aim of our research was to compare the mechanism of degradation

silicate-based coatings on Mg-based implants. 

Materials and methods: Our study attempted to examine the corrosion behavior of Mg-based samples with silicate coating in a different environment. Samples were immersed in three different solutions: cell culture media DMEM/F12, PBS (phosphate buffer saline), and saline. The surfaces of the samples were examined and characterized with an optical microscope, scanning electron microscopy, weight loss measurement.

Results. It was observed that the corrosion in-vitro was visualized macroscopically by the ganging of the surface color. The silicate coating dissolved in all solutions. Local sites of corrosion were observed in the case with saline and PBS solutions. The degradation rate of the samples in saline solution was lower compared to other solutions. 

Conclusion: Magnesium and its alloys have unpredictable corrosion in DMEM/F12 and PBS solutions mainly due to the presence of numerous ions in the fluids (e.g., Na+, K+, Ca2+, СО32+etc.). Therefore, corrosion prediction is a complicated task. Consequently, to study the corroded surface chemistry we have to conduct additional EDS (Energy-Dispersive Spectroscopy) test.

Acknowledgment: This research was funded by Ministry of Education and Science of Ukraine 0119U100823.