Corrosion behavior of Mg–Bi–Ca alloys prepared via high vacuum melting as biodegradable materials in Hank solution

Abstract

The study investigated the corrosion behavior of Mg–Bi–Ca alloys in a balanced Hank solution through potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS). Corrosion potential (Ecorr), Current density (Icorr), Corrosion rate (CR), Impedance modulus (|Z|) and phase angle parameters were employed to analize the electrochemical test results. The effects of the quantity and distribution of the different phases, as well the percentage of Bi in the alloys, were assessed. The cell compatibility results indicated that both alloys are suitable for use as biodegradable implants, and the electrochemical testing results demonstrated that the primary corrosion mechanism observed in the alloys is continuous anodic dissolution, meaning the material steadily dissolves without forming a protective passivation layer. The behavior of impedance modulus and phase angle, which are indicators of the material's resistance to corrosión, were influenced by the reactions occurring at the material-electrolyte interface and the types of corrosion products formed. Additionally, the content of Bi in the alloys plays a role in determining these behaviors, particularly the eutectic phase. According to the CR criteria, the as-received Mg–4 %Bi–1 %Ca alloy in Hank solution at 37 °C is the most suitable for the fabrication of biodegradable implants.