Copper Corrosion in Binary Deep Eutectic Solvents: Role of Physicochemical Properties

ABSTRACT Deep eutectic solvents (DESs) are promising electrolytes for electrochemical processes owing to their composition, which can be tuned to modify viscosity, ionic conductivity, acidity, and metal‐ligand interactions. These properties can strongly influence corrosion of metallic substrates, yet comparative studies linking DES chemistry to copper corrosion remain limited. In this study, the corrosion behavior of copper in four binary DESs—Ethaline (ChCl:ethylene glycol, 1:2), Reline (ChCl:urea, 1:2), Oxaline (ChCl:oxalic acid, 1:1), and Glyceline (ChCl:glycerol, 1:2)—was investigated using Tafel polarization and ICP‐OES, with selected physicochemical properties used to interpret the corrosion response. Oxaline showed the highest copper dissolution, reaching 1429.866 ± 1.223 mg/L after 2 h at 85°C, whereas Glyceline showed the lowest value (73.744 ± 0.504 mg/L). Ethaline combined the lowest viscosity (20 mm 2 s −1 at 40°C) with high ionic conductivity and comparatively low copper dissolution (80.548 ± 0.011 mg/L after 2 h). The results indicate that HBD chemistry, particularly acidity and hydrogen‐bonding interactions, is the principal chemical factor governing copper dissolution, while viscosity and ionic conductivity regulate mass transport. Thus, Glyceline provides the lowest measured Cu dissolution, whereas Ethaline offers a practical balance between corrosion resistance and ion transport for copper‐based electrochemical applications.