Electroforming Thin Fe Foils Using ChCl/Urea Deep Eutectic Solvent: Effects of MnCl ₂ and Current Density on Microstructure and Corrosion Behavior

ABSTRACT Deep eutectic solvents (DESs), a class of ionic liquids, have recently been proposed as promising candidates for metal electrodeposition. Specifically, using DESs over aqueous solutions allows the reduction of metals with negative cathodic potential (i.e., Mn) without significant side reactions, such as the evolution of hydrogen gas, which is responsible for embrittlement phenomena. The current work assessed the nonaqueous electrolytic deposition of Fe and Mn using DESs for temporary biomedical devices (e.g., coronary stents). The DES was obtained by mixing choline chloride (ChCl) and urea. The samples were produced using three current densities (20, 30, and 40 mA/cm 2 ). The surface morphology and chemical composition were assessed by scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDS), electron probe microanalysis (EPMA), and transmission electron microscopy (TEM). Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were performed to study the corrosion behavior of the electroformed samples. TEM and EDX analyses revealed that Mn incorporates into the Fe matrix by doping with Fe 2 O 3 . A needle‐shaped nanostructure is reported for the first time in electroformed Fe. Among the conditions, electroformed samples at 30 mA/cm 2 present the best compromise between Mn incorporation, microstructural homogeneity, and corrosion resistance, with a rate of 0.41 mm/yr in Hanks' solution. These findings highlight the potential of electroformed Fe‐based materials for biodegradable applications through microstructural and compositional control.