Ionic Liquids Based on Chromotropic Acid: Excellent Lubricating Additives for Aqueous System

In this paper, four ionic liquids based on chromotropate (CAILs) were prepared and applied to heighten the tribological performance of aqueous system on different metal friction contacts. Taking for the potential choice for water-based lubricating additive, CAILs exhibited excellent water solubility and corrosion resistance. Tribological results showed that the CAILs, especially the phenolic hydroxyl group decorated samples (TsnN 4444 and TsnP 4444 ), demonstrating extremely effective lubricating properties with the efficient friction and wear descent (69% and 83% for Fe, 47% and 94% for Cu, 74% and 69% for Al, respectively). Especially, the excellent load-carrying capacity was also presented with the highest P B (833 N) and P D (1568 N) values for TsnP 4444 . It is speculated that the CAIL molecular adsorption on the interface and further generation of tribochemical films are beneficial for their lubricating effects, resulting from the systematic discussion and analysis of CA, QCM, SEM, XPS, and FIB-TEM tests. However, TsN 4444 and TsP 4444 showed less effective lubricating performances and poor load-carrying capacities due to tribocorrosion of hydroxyl groups at the interface. Graphical Abstract