Foam inhibition is an important function of a motor oil’s additive system.
We expect foam in our shaving creams, building insulation and lemon meringue pie. We do not, however, expect it in our lubricants. Air can easily get into fluid system and become trapped within, causing foam to billow up. The presence of foam in a lubricant is very harmful, seriously hampering its cooling and lubricating abilities.
It is the job of a specialized group of additives known as defoamers to inhibit foam. Without these important defoamers, foam would ooze out of your vehicle’s dipstick, you’d get a spongy response from automatic transmission fluid and harmful cavitation in hydraulic pumps. In short, without foam inhibitors, motor oils and lubricants would not be able to do their job.
The challenge of choosing the most effective and fastest defoamers for each lubricant application is usually left up to additive suppliers. According to Ken Fey of Dow Corning, “In automotive engine oils, gear oil and hydraulic fluids, the major defoamer customers are additive package formulators. Antifoam is one part of that package, yet it can be almost an afterthought, unfortunately.”
Most defoamers work in such a way as to alter the surface tension of the fluid so bubbles cannot be sustained long enough to cause foaming. “Foam control is a balance between the material to be defoamed and the defoamer,” says Fey. “You want it to be insoluble in the defoamed medium, but also dispersible.”
Careful additive selection has become increasingly important over the past few years, and additive suppliers and lubricant formulators will need to continue paying close attention to the quality of the defoamers they purchase. According to Gary Winfield of Solutia, “The next generation of oils are going to have to deal with smaller engines, hotter conditions, higher rpm. That all means more heat and stress on the defoamer, and at the same time the requirements are going to demand more protection.”
Foam inhibition is especially important for high quality lubricants like AMSOIL, which are used for extended drain intervals. Christian Crawford of Ross Chem, a defoamer manufacturer for the metalworking industry, agrees. “We see the marketplace asking for products that are better for high-pressure operations, that have more stability, and more persistence over time,” says Crawford. “Manufacturers are pushing the outer boundaries of their fluid now, keeping fluids for weeks and months longer than before, and they want the fluid’s defoamer to last all that time, too.”
Craig Zychal of Ultra Additives, also in the metalworking additive industry, sees special challenges for defoamers in metalworking fluids. “Since metalworking fluids are primarily used in an open system environment, there are more opportunities for foam-causing agents to contaminate the fluid, such as dirt and bacteria from the environment, leaking hydraulic systems, and constant ‘make-up’ additions from other metalworking fluid components,” says Zychal. “Also thee are numerous conditions that lead to defoamer extraction. The potential affinity for metal fines, adhesion to the work piece, and continuous filtration and recycling systems all impact a defoamer’s prospect for success.
AMSOIL prides itself on its careful selection of additive systems, refusing to settle for anything but the very best. Each AMSOIL lubricant contains the highest quality additives, including top-of-the-line defoamers which perform under the most extreme conditions and over extended drain intervals.
Foam inhibition is an important function of a motor oil’s additive system.
