Depending on the application, metalworking fluids may be entangled with various additive functions, including corrosion inhibitors, biocides, emulsifiers, lubricity, and rust inhibitors. Calcium metal sulfonate has strong conditioning properties and excellent corrosion protection, and sodium is considered an excellent emulsifier for water-based rust and fume protection in acidic environments. The next generation of rust will be ashless. They do not carry any heavy metals and do not leave heavy metal residues on the workpiece. The upstream trend towards lower Class I wax production means that less sparse wax is available for RP.
For formulations that can be used on both ferrous and ferrous metals but are not compatible with non-ferrous metals, formulators may need to passivate them with a Corrosion Inhibitor such as alkyl phosphate. This additive will help neutralize stains and provide an excellent finish on aluminum. Phosphates can also provide additional antiwear properties. Imidazolines and amides are effective corrosion inhibitors for ferrous metals, especially imidazolines require low concentrations. Emulsifiers are special molecules that form a physical barrier that prevents droplets from coalescing. Carboxylate, sulfonate, and PIBSA salts are common anionic emulsifiers, are negatively charged, and function as primary emulsifiers. Amides, esters and ethoxylates are uncharged nonionic emulsifiers that act as co-emulsifiers. A third class of emulsifiers, cationic, are demulsifiers and include amine salts and phospho compounds. Cationic emulsifiers are positively charged. N,N-Methylenebismorpholine (MBM), the most common fungicide in Asia, is the reaction of morpholine with formaldehyde, in which the formaldehyde content is about 20%. MBM is suitable for in-formulation and tank-side because the finished product can stay in the barrel for a long time with little to no cracking. Triazines are a class of nitrogen-containing heterocycles that are among the cheapest biocides on the market. Many formulators use it because it is inexpensive. If customers have emulsion or microbial issues, triazines are an effective option for "quick kills", but formulations have poor long-term stability and are prone to separation or splitting. It's not a great option for the finished product itself. MBO 3,3-methylene biz [5-methyl]-1,2-oxazolidine (MBO) is the reaction of formaldehyde and monoisopropanolamine for formulation side and tank side applications. Although MBO is not as effective as MBM, it is more effective than triazine for formulation stability in drums. For customers requiring formaldehyde-free biocides, methylchloroisothiazolinone and methylisothiazolinone (CIT/MIT) are recommended. The reduction of human touches due to improvements in the Internet of Things (IoT) and robotics requires further compatibility requirements for fluids throughout the process. Customers' demands for longer tank life and reduced waste are driving the shift to synthetic and semi-synthetic emulsions.
