Degradation characteristics of Mg0.8Ca in saline solution with and without albumin protein investigated by electrochemical impedance spectroscopy

Biodegradable magnesium-calcium (MgCa) alloy is a very attractive biomaterial. Binary Mg0.8Ca alloy was fabricated. X-ray diffraction (XRD) analysis and optical microscopy observed showed that Mg0.8Ca alloy was composed of alpha(Mg) phase. The electrochemical impedance spectroscopy (EIS) technique was used for the study on the degradation characteristics of Mg0.8Ca alloy. Because the proteins have a role on the passivation of metals, the effect of albumin protein addition in NaCl solution on the electrochemical behaviour of Mg0.8Ca alloy was studied. It has been shown that in 0.9wt% NaCl solution the impedance was mainly characterised by one capacitive and one inductive effect, which related to the alloy charge transfer reaction and the relaxation of the absorbed corrosion compounds. The addition of 37.5 mg/mL albumin protein to 0.9wt% NaCl solution increased the impedance compared to that without albumin protein. The equivalent circuits simulating the electrochemical behaviour of Mg0.8Ca alloy in 0.9wt% NaCl solution with and without albumin protein were proposed. The surface morphology of the Mg0.8Ca samples after 1-week immersion in Mg0.8Ca alloy in 0.9wt% NaCl solution with albumin protein was studied using scanning electron microscopy (SEM). The electrochemical mechanism for degradation of Mg0.8Ca alloy in 0.9wt% NaCl solution is related to the albumin protein addition.