New formulation of metalworking fluids using emulsifiers and alkanolamines for enhanced resistance to microbial degradation

Water-miscible metalworking fluids (MWFs), commonly used in metal forming operations, are lubricants that must be safe for direct human contact. The proper selection of materials in a new metalworking fluid, while being environmentally friendly, helps to inhibit microbial growth, reduce operational issues, extend tool life, and ultimately lower costs. A common issue with MWFs is microbial degradation by bacteria and fungi, which is facilitated by available nutrients, such as carbon, at population densities exceeding 10⁶ CFU/ml. In this study, alkanolamines, oleic acid, and boric acid were evaluated for their effectiveness as antimicrobial agents. The inherent biological resistance of the MWF was assessed using an unknown biological inoculum collected from a device at Iran's Tractor Manufacturing Company, in accordance with ASTM E2275 standards. The results indicated that the new fluid, in the absence of conventional biocides, maintained its inherent biological resistance for more than five weeks.