Uses of Borates in Lubricants & Greases
From the birth of civilization, inscriptions from archeological excavations suggest examples of lubrication systems using animal fat to reduce the friction on the axle of chariot wheels.
Found in the grave of Egyptian king Tehut-Hetep (1650 B.C.), olive oil was apparently a lubricant of choice to be applied to wood planks when moving large stones.
During the middle ages (450-1450 AD) progress was made to improve lubricants. It was not until the 1850s when Colonel William Drake found oil in 1859 marking the birth of the petroleum industry. However, petroleum products in their early years did not perform well versus animal fat (tallow). In the 1920s the lubrication industry began processing crude petroleum oil to improve their performance.
By 1930, solvent-based petroleum chemistry began emerging, and developed technology that improved base oil performance. Additives began to be introduced in 1947 to extend the life of refined oils.
It is believed that the uses of borates as a lubricant (boric acid) came in the 1940s when ester chemistry and more specifically, polyol esters began to be used as additives.
In 1950, multigrade oils were introduced to provide alternative oils for extreme temperatures during hot and cold environments. Since this time, additives have been improved to further extend and enhance lubricating oil’s performance.
Industrial fluids generally include antifreeze, brake fluids, lubricants (oil and grease), metalworking fluids, and water treatment chemicals. For the purposes of this review we will be discussing lubricants and greases.
- Active Lubricant
- Boresters – Soluble source of borate
- Corrosion inhibitor (anodic inhibitor)
- Reduction in carbonaceous deposits
- Reduction of sludge formation
The primary purpose of lubrication is to reduce wear and heat between
contacting surfaces in relative motion. While wear and heat cannot be completely eliminated, they can be reduced to negligible or acceptable levels. Because heat and wear are associated with friction, both effects can be minimized by reducing the coefficient of friction between the contacting surfaces.
Lubrication is also used to reduce oxidation and prevent rust, to provide insulation value, to transmit mechanical power in hydraulic fluid applications, and to seal against dust, dirt, and water.
Lubricants reduce wear and heat by inserting a lower-viscosity (shear strength) material between wearing surfaces that have a relatively high coefficient of friction. In effect, the wearing surfaces are replaced by a material with a more desirable coefficient of friction. Any material used to reduce friction in this way is a lubricant. Lubricants are available in liquid, solid, and gaseous forms. Industrial machinery ordinarily uses oil or grease. Solid lubricants such as molybdenum disulfide or graphite are used when the loading at contact points is heavy. In some applications the wearing surfaces of a material are plated with a different metal to reduce friction.
Grease is a semifluid to solid mixture of a fluid lubricant, a thickener, and additives. The fluid lubricant that performs the actual lubrication can be petroleum (mineral) oil, synthetic oil, or vegetable oil. The thickener gives grease its characteristic consistency and is sometimes thought of as a “three-dimensional fibrous network” or “sponge” that holds the oil in place. Common thickeners are soaps and organic or inorganic nonsoap thickeners. The majority of greases on the market are composed of mineral oil blended
with a soap thickener. Additives enhance performance and protect the grease and lubricated surfaces. Grease has been described as a temperature-regulated feeding device: when the lubricant film between wearing surfaces thins, the resulting heat softens the adjacent grease, which expands and releases oil to restore film thickness.
The function of grease is to remain in contact with and lubricate moving surfaces without leaking out under gravity or centrifugal action, or being squeezed out under pressure. Its major practical requirement is that it must retain its properties under shear at all temperatures subjected to during use.
Borates Uses in Lubricants & Greases
Borates’ value in lubrication, relates to boric acid and its natural crystalline structure which is very lubricious due to its natural crystalline structure. The borate compound consists of crystalline layers in which the atoms tightly adhere to each other that helps to reduce the coefficient of friction. However, the layers are relatively far apart, so the intermolecular bonds (Van der Waals forces) are rather weak. When put under stress (such as in lubricants), the layers tend to slide over one another very easily. The aforementioned strong bonding within each layer can prevent direct contact between sliding parts, lowering the friction and minimizing wear. Another value of boric acid is its compatibility with other lubrication additives.
Engine wear is a constant concern, in particular to the automotive and heavy construction equipment industry. Borate polyols and polyamines in lubricants form very good resilient lubricious films on metal load-bearing engines and other moving parts. This film improves the load capacity and protects from future wear and tear. Borester chemistry plays an important role by causing boric acid to react with alkanolamines to form soluble borester compounds. It is this form of organic borate compound that allows borates to be incorporated into lubricants and greases.
Boron containing additives in lubricants have properties such as anti-rust, anti-knocking, detergent, low sludge formation, lubrication, and reduction of carbonaceous deposits.
Another area of interest is nanotechnology where boric acid is being ground several times down to approximately 50 nanometers. This finely ground material is blended with various synthetic lubricants to create a suspension that will prevent the nano-based boric acid from falling out of the suspension. This has resulted in significant improvement in the lubricous nature of boric acid and the lubricant.
Other Borate-based Industrial Fluid Applications
- Brake Fluids
- Metalworking fluids
- Water treatment
American Borate Company Products: