High‐Resolution Corrosion Fingerprinting of Alloy Libraries via Microdroplet Spectroelectrochemistry

A rapid and reliable methodology for assessing localized corrosion is essential for the early‐stage of advanced alloy systems. Here, we present an ionic‐liquid‐based microdroplet electrochemical platform that overcomes the time limitations of conventional aqueous droplets by using nonvolatile electrolytes. This approach enables stable long‐duration electrochemical measurements and systematic multidroplet experiments under controlled conditions. Electrochemical impedance spectroscopy (EIS) was performed in confined electrolyte droplets over a wide frequency range (100 kHz–10 mHz) to probe the localized electrochemical behavior of aluminum alloys. The influence of droplet wetting and geometry on the impedance response was quantitatively analyzed using finite‐element simulations based on the actual droplet configuration. These simulations identify wetting‐induced geometrical effects, particularly in the high‐frequency domain. The methodology exhibits high reproducibility across multiple droplets and remains robust over extended exposure times and varying droplet volumes. The platform was further coupled with operando micro‐Raman spectroscopy to demonstrate simultaneous electrochemical and spectroscopic measurements within a confined droplet. The reversible Ni(OH) 2 /NiOOH redox transition was monitored in alkaline media, validating the spectroelectrochemical coupling. Overall, ionic‐liquid microdroplet spectroelectrochemistry provides a versatile platform for localized electrochemical characterization and comparative corrosion screening, with strong potential for high‐throughput materials evaluation and data‐driven alloy development.