N-Heterocyclic Carbene Overlayers on Mild Steel

Although the functionalization of noble metals with N-heterocyclic carbenes (NHCs) is well-known, the interactions of these versatile ligands with common alloys are not. Herein, we present an immersion-deposition approach that enables the modification of mild steel (MiS) with diisopropylbenzimidazolium hydrogen carbonate (^iPrNHC·H₂CO₃). The NHC-modified surface was characterized by X-ray photoelectron spectroscopy, angle-resolved X-ray photoelectron spectroscopy, atomic force microscopy-based infrared spectroscopy, time-of-flight secondary ion mass spectrometry, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. These experimental methods provide support for the functionalization of mild steel with ^iPrNHC and for the reduction of surface oxide by the carbene. Electrochemical analyses and salt immersion tests were also performed and they showed that the NHC coating increases the corrosion resistance of MiS. This study demonstrates that immersion deposition is a viable method for the modification of mild steel surfaces with N-heterocyclic carbenes and shows the potential for mitigating corrosion.