Glass-like cerium sol-gel coatings on AZ31B magnesium alloy for controlling the biodegradation of temporary implants

- Pure Ce and Ce/Si coatings on Mg alloy are adherent promoting HA when immersed in SBF.
- The degradation rate of Ce/Si films is much lower than that of Mg substrate.
- Pure Ce and Ce/Si coatings are proposed to control biodegradation of Mg implants.

Mg alloys are a good alternative to be used as biodegradable and resorbable implants, but its rate of degradation in the body is too fast. In this work, two types of coatings are studied to control the corrosion speed and to improve the corrosion resistance of magnesium alloy in simulated physiological environment. First, glass-like cerium-based coatings (CexOy) were prepared using cerium nitrate and various complexing agents, deposited by dip-coating and heat treated at 250 °C for 10 min. On the other side, a silica sol was prepared by acid catalysis with ethyltriethoxysilane (TEOS) and deposited by dip-coating on the CexOy coatings. The characterizations of single (CexOy) and double layer (CexOy/SiO2) coatings included adhesion tests and wettability by contact angle measurements. Furthermore, immersion tests were performed using the simulated body fluid (SBF) at 37 °C assessing the change in pH, hydrogen evolution and mass loss of the coated and uncoated alloys as a function of the immersion time. The coated substrates showed suitable adhesion behaviour and SBF tests demonstrated that degradation speed of the substrate is reduced by the deposition of the coatings.