Biodegradable metallic materials: A measuring approach to predict the corrosion rate

The bone surgery often makes use of implants to sustain and fix the bones during the healing phase. Commonly used implants require a surgical procedure to be removed after bone healing, so there is a strong demand for a new typology of bio-absorbable implants. To design biodegradable implants one has to find a material with good mechanical characteristics coupled to the capability of being corroded by the body fluids without releasing toxic compounds. Notwithstanding the commercially available magnesium alloys possess several of the positive required properties, the magnesium corrosion rate in the body is too high with respect to the bone healing rate. Innovative alloys designed by alloying magnesium with other metals already present in human body may overcome this problem. The choice of the proper alloy is supported by the development of a measuring approach which can allow to assess the corrosion rate as a function of the alloy composition, and to gain knowledge on the degradation mechanism and kinetics. In this paper EIS (Electrochemical Impedance Spectroscopy) measurements are proposed because they may be carried out on devices of any shape and size and with different electrolytes provided that their conductivity is high enough in comparison to the impedance of the device surface. Our experimental findings show that EIS is noticeably promising to assess the corrosion behavior of bio-adsorbable implants.