Influence of ultra-fine grain structure on corrosion behaviour of biodegradable Mg-1Ca alloy

Abstract Biodegradation studies of Mg-1Ca alloy with different microstructures in Ringer’s solution reveal corrosion mechanism based on the balance between the anodic dissolution of the secondary phase and hydroxide precipitation, controlled by the secondary phase size and distribution uniformity. Alloy with ultrafine-grain structure shows at least 5-fold improvement in corrosion resistance compared to the coarse-grained alloy due to the separation of the particles of the secondary phase and its continuous intragranular nano-precipitation. This promotes an unusual low-frequency impedance behaviour described by an inductive loop with the negative time constant, which leads to the increased impedance modulus signifying the improved corrosion resistance.