The Chemistry of Metalworking Fluids
Metalworking fluid formulations are relatively complex compared with other lubricants because they must provide multiple functions when used. The main types of metalworking fluids used in metal removal fluids and metalforming fluids are straight or neat oils, emulsifiable oils, semisynthetic fluids, and synthetic fluids. Straight oils represent the traditional metalworking fluid type that was in use at the beginning of the Industrial Revolution. The main mineral oil basestock used in metalworking fluids is naphthenic oils. Compared with paraffinic base oils, naphthenic oils act as better solvents, which is a major requirement due to the large number of functional additives used in complex metalworking fluid formulations. The most commonly used reserve alkalinity boosters are monoethanolamine (MEA) and triethanolamine (TEA). In the past, diethanolamine (DEA) was also used, but due to regulatory concerns the metalworking fluid industry has discontinued the use of this amine. Other amines used include monoisopropanolamine (MIPA) and diglycolamine (DGA).