Coated Copper Self-Repairs

A new type of ionic liquid containing anionic molecular metal oxides not only protects copper surfaces from acid corrosion, but also enables scratched surfaces to repair themselves (Angew. Chem. Int. Ed. 2014, DOI: 10.1002/anie.201408171). Carsten Streb and Sven Herrmann at Ulm University, in Germany, and colleagues developed a new version of so-called polyoxometalate-based ionic liquids (POM-ILs). The ionic liquids were composed of transition-metal-functionalized Keggin (silicon tungstate) anions and quaternary alkylammonium cations. Previous research has shown that solid POM salts could inhibit corrosion, so the authors tested their POM-IL on copper disks. They found that their POM-IL coating, which is viscous and hydrophobic, was superior not only to solid POM but also to commercial ionic liquids in protecting the copper disks from corrosion by acetic acid vapor and acid rain droplets. In addition, when copper disks coated with the POM-IL were scratched, the disk repaired itself within one minute. The authors envision that such coatings could be used to protect other acid-sensitive materials such as marble.