Solvent and aqueous cleaning agents can both be effective degreasers. Take a few minutes to understand how your cleaning agent of choice works. Effective critical cleaning is a must for profitable manufacturing. The more you understand how degreasers work, the easier it is to put together effective critical cleaning processes.
To understand cleaning agents we need to get into a little bit of chemistry. This won’t hurt… promise! An organic chemical does not mean one that is produced free-range without pesticides. Organic solvents are made of molecules containing one or more atoms of carbon. Like dissolves like. Mineral spirits and many other organic solvents are inherently effective in dissolving oils because both oils and mineral spirits are organic chemicals. Water, even from a pristine mountain stream, is inorganic because H20 does not include carbon. Water is polar, so it dissolves table salt and other polar soils. However, in the world of parts cleaning and critical cleaning, solvent means organic solvent.
Aqueous cleaning sometimes involves cleaning with water alone or, more often, cleaning with a blend of water plus organic and inorganic additives. Aqueous degreasers are usually supplied as a powder or a concentrated liquid and then diluted with water before use. Aqueous cleaners can be very effective in removing mixtures of soils that contain both polar and nonpolar chemicals. Rather than wading through long lists of polysyllabic chemicals (a sure cure for insomnia) it is more productive to think of the additives to water in terms of their function. Some important functions include wetting, solubilization, saponification, emulsification and sequestration.
Surfactants (a word derived from “surface active agents”) are organic compounds. Their roles include wetting, cleaning efficiency, lubrication, solvency and rinsing properties. Wetting is an important function, especially if the parts being cleaned are not completely flat. With improved wetting, the aqueous cleaning agent is better able to access more complex areas of the product. Surfactants have a hydrophilic end and a hydrophobic end. The hydrophilic end likes water. The hydrophobic end is attracted to oils and greases.
Molecules of surfactants remove soils and hold soils away from the surface in suspension by the process of micelle formation. Micelles are little “globs” of nonpolar soil that are surrounded by surfactant molecules with the oily soils attracted to the hydrophobic end of the surfactant. Micelles and many other aqueous additives have to be rinsed, particularly in critical cleaning applications.
We also have to consider whether the aqueous cleaning agent is acidic, basic (alkaline) or neutral. Aqueous cleaning agents that are effective in removing oils, greases and associated metalworking fluids are generally basic; some are neutral. Acidic cleaners are effective in removing inorganic compounds and surface oxides. If you are not sure what you have, look at the SDS (MSDS) and check the pH. pH levels between 6 and 9 are often considered to be neutral or near-neutral. Acid cleaners have a pH is less than 6. Alkaline cleaners have a pH higher than 9. Remember that the pH scale is logarithmic, so a pH difference of 1 reflects a 10-fold difference in acidity or alkalinity. The demarcation between classes of cleaners are arbitrary; experts disagree. The higher the pH, the more caustic. Caustic degreasers may be more effective, but there could be greater potential damage to the product and to people. Additives may be used to increase the effectiveness of near-neutral pH products.
A great deal of sophisticated chemistry, in terms of reactions and blending, is involved in producing aqueous cleaning agents. Synthetic chemists design the molecules that are used as ingredients in the product, which typically involves chemical reactions. The field is very specialized; some synthetic chemists have distinguished careers designing surfactants for specific applications. In the case of biobased products, at least some of the molecules may be synthesized by plants or other life forms and a chemist may be involved in changing those molecules. Formulation chemists could be considered technical chefs. They design and blend the ingredients (the specific molecules) to produce the cleaning agent.
We periodically run into manufacturers who attempt to blend their own aqueous cleaning chemistries. This is not a good idea. Given the many possible ingredients involved in aqueous degreasers, we suggest that you leave formulation, let alone synthesis, to the specialists. Your role as a chef is in developing and controlling the process. This involves initial testing. And don’t forget the water! Even the most carefully-designed aqueous cleaning agent needs a clean and consistent source of water.