Pure iron has been demonstrated as a potential candidate for biodegradable metal stents due to its appropriate biocompatibility, suitable mechanical properties and uniform biodegradation behavior. The competing parameters that control the safety and the performance of BMS include proper strength-ductility combination, biocompatibility along with matching rate of corrosion with healing rate of arteries. Being a micrometre-scale biomedical device, the mentioned variables have been found to be governed by the average grain size of the bulk material. Thermo-mechanical processing techniques of the cold rolling and annealing were used to grain-refine the pure iron. Pure Fe samples were unidirectionally cold rolled and then isochronally annealed at different temperatures with the intention of inducing different ranges of grain size. The effect of thermo-mechanical treatment on mechanical properties and corrosion rates of the samples were investigated, correspondingly. Mechanical properties of pure Fe samples improved significantly with decrease in grain size while the corrosion rate decreased marginally with decrease in the average grain sizes. These findings could lead to the optimization of the properties to attain an adequate biodegradation-strength-ductility balance.

This article reports a degradation study that was done on stent prototypes made of biodegradable Fe35Mn alloy in a simulated human coronary arterial condition. The stent degradation was observed for a short‐term period from 0.5 to 168 h, which simulates the early period of stenting procedure. Potentiodynamic polarization and electrochemical impedance spectroscopy were used to quantify degradation rate and surface property of the stents. Results showed that signs of degradation were visible on both crimped and expanded stents after 1 h of test, mostly located on the stent's curvatures. The degradation rate of stent was higher compared to that of the original alloy, indicating the surface altering effect of stent fabrication processing to degradation. A single oxide layer was formed and detected as a porous structure with capacitive behavior. Expanded stents exhibited lower polarization resistance compared to the nonexpanded ones, indicating the cold work effect of expansion procedure to degradation. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 572–577, 2015.

The first example of a documented electroforming process dates back to 1837 when a layer of electrodeposited copper was found on the surface of a printing plate. Since then, it became a basic manufacturing process to produce delicate metallic components such as nickel thin foils for solar panels, perforated screenprinting cylinders used for fabric and carpet printings, digital recording devices, etc. Recently, electroforming is used for the fabrication of iron-based materials designed for cardiovascular stents. Electroformed iron shows a higher corrosion rate in simulated biological environment; this behaviour is supposed to be influenced by its microstructure which is finer than that of iron produced with traditional techniques. A high corrosion rate can be beneficial for cardiovascular stent applications: a complete stent dissolution in 12-18 months can effectively prevent both late thrombosis and further treatment of paediatric patients, usually requiring a continuous vessel remodelling. Faster corrosion rate of iron-based material is advantageous for cardiovascular stent application in order to avoid late stent thrombosis and arterial growth mismatch in young patients leading to a secondary revascularization procedure. Electroformed iron has mechanical properties comparable to those of stainless steel (stent reference metal) with the advantage of the total dissolution of the material after the accomplishment of its function: for this reason, this metal can be considered as a valid alternative to magnesium-based materials. Nevertheless, electroforming is influenced by parameters such as electrolyte bath composition, current density, pH, temperature, additives, cathode, etc. that have a significant effect on the structure of the produced materials.

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