Effect of glycerol-citrate polymer coating on structural, corrosion and antibacterial properties of biodegradable iron foam

Biodegradable iron scaffolds are attractive materials for temporary orthopedic implants, however, their slow corrosion rate limits clinical applicability. Herein, we introduce a simple surface-modification strategy to accelerate the degradation of open-cell iron foams by applying a thin thermoset glycerol–citrate (GCA) polyester coating. Iron foams were dip-coated with thin GCA layer and thermally cured at either 135 °C (Fe-GCA-135) or 165 °C (Fe-GCA-165). Structural and surface properties were evaluated using SEM, BET, XRD, and XPS analyses, while corrosion properties were assessed by potentiodynamic polarization in Hanks’ solution at 37 °C. Antibacterial activity was examined against Staphylococcus aureus and Escherichia coli under direct-contact conditions using viable colony counts. The Fe-GCA-135 scaffold exhibited the highest corrosion rate (0.90 mm·year⁻¹) and corrosion current density (0.077 µA·cm⁻²), indicating substantially accelerated degradation compared to bare iron (0.20 mm·year⁻¹). A strong bactericidal effect was observed with more than an eight-log reduction in viable cells for both strains after 24 h incubation. In contrast, Fe-GCA-165 showed a lower corrosion rate (0.61 mm·year⁻¹) and reduced antibacterial activity (3–4 log reduction), consistent with a less uniform coating observed by SEM. This work demonstrates a bifunctional application of thermosetting GCA coatings on biodegradable iron foams, enabling simultaneous enhancement of degradation kinetics and intrinsic antibacterial protection which represents a promising approach toward next-generation bioresorbable iron implants.