Accelerated biodegradation of Fe-30Mn-S biocomposite via preferential corrosion of secondary phase

Biomedical Fe-30Mn alloy was a promising alternative for the repair of load-bearing bone defects, but its applications were largely limited by slower degradation rate than growth rate of natural bone. The accelerated corrosion mechanisms of secondary phase MnS in Fe-30Mn-S biocomposite were proposed in the study. Detailly, the MnS with a lower corrosion potential preferentially corroded and thereby increased corrosion active sites. Moreover, adsorbed S element produced by the corrosion of MnS weakened the metal-metal bond of Fe. Meanwhile, Cl⁻ with a small ion radius easily penetrated through degradation products, which made corrosive media inside corrosion pits more aggressive. Thus, the Fe-30Mn-S biocomposite tended to vertically expand during corrosion evolution, and caused rapid corrosion with a considerably increased corrosion rate of 0.41 mm y⁻¹. Besides, the Fe-30Mn-S biocomposite presented an ultimate compressive strength of 687 ± 22 MPa, compressive yield strength of 402 ± 23 MPa, microhardness of 280.4 ± 5.8 HV, and favorable cytocompatibility. These results indicated that Fe-30Mn-S biocomposite with accelerated corrosion effects by secondary phase could be a promising candidate for bone repair.