Potassium Pentaborate

Potassium Pentaborate

Strength and versatility

This product’s unique capabilities make it ideal for the automotive industry, where its addition to gear lubricants improve load-carrying capacity and wear protection.

Potassium Pentaborate used in industrial lubricants

Wide-Ranging Benefits

20 Mule Team® Borax potassium pentaborate is a mild alkaline salt that results from the controlled reaction of potassium hydroxide, water, and boric acid. The product has a variety of uses, from welding and drilling to automotive to photographic development.


Metal refining and metallurgy

Borates are used as cover fluxes in metal refining. Potassium pentaborate is an excellent choice for copper refining, copper alloys, and precious metals. As an alternative to typical fluorine-containing flux compounds, potassium pentaborate can help reduce fluorine emissions.

When using silver soldering, brazing, or welding to join metals, use potassium pentaborate by itself or mixed with other materials to create a borate-containing flux. This flux melts and dissolves oxide impurities on the metal surfaces that are being joined and provides a protective barrier film that prevents further oxidation. Use potassium pentaborate in fluxes for stainless steel or various non-ferrous metals to avoid the glare that is associated with sodium borate.

Gear lubrication

When dispersed in a very finely divided state, potassium borates improve the load-carrying, anti-corrosion, and anti-wear properties of industrial and automotive gear lubricants. Under extreme conditions, potassium pentaborate interacts with metal load-bearing surfaces to form a film of extraordinary resilience. This tenacious film provides outstanding load-carrying capacity and wear protection, making the product an ideal fit in automotive lubricants.

Oil well drilling

Slow-setting cements can be pumped to great depths before hardening during oil well drilling. The addition of soluble borates such as potassium pentaborate delays the set of the cement.

And, more

Other uses include in photographic development, where potassium pentaborate can be used as the source of borate anion. In a complex with cationic dye, the product can then be combined with a nonionic aromatic diazo compound to create a light-sensitive composition for use as a diazotype developer.

Potassium pentaborate solutions are also used to treat wooden and paper matches to control the burn rate of the match and to stop afterglow.


Automotive assembly line for gear lubrication

Potassium pentaborate’s unique capabilities make it ideal for the automotive industry, where its addition to gear lubricants improves load-carrying capacity and wear protection.


Potassium Pentaborate APPLICATIONS
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This soluble borate can be used in the production of slow-setting cement for oil well drilling.



Available Grades

Potassium pentaborate shows little tendency to cake, except after prolonged storage or if it becomes severely wetted by rain or substantial water penetration. It can also absorb moisture if exposed to a humid environment.

Heated in a vacuum, the crystalline salt begins to lose water at about 220°F (105°C) and continues to lose molecules of water up to about 932°F (500°C). The anhydrous form fuses to a clear glass at 1435°F (780°C).

Aqueous solutions of potassium pentaborate show decreasing pH with increasing concentration.


Chemical and Physical Properties

Molecular weight: 239.21

Specific gravity: 1.74

Appearance: White crystalline granules

Melting point: 1436°F (780°C)

Solubility: 4.3% (as KB5O8·4H2O) by weight in water at room temperature

Stability: When stored under normal conditions of temperature and humidity, potassium pentaborate is unlikely to change chemically or to cake.

Chemical Composition (Theoretical)

Boric oxide, B2O3: 59.36%

Potassium oxide, K2O: 16.06%

Water of crystallization, H2O: 24.58%

Anhydrous equivalent, KB5O8: 75.42%

Containers: Products may be available in bulk, IBCs, or small bags

U.S. Borax, part of Rio Tinto, is a global leader in the supply and science of borates—naturally-occurring minerals containing boron and other elements. We are 1,000 people serving 650 customers with more than 1,800 delivery locations globally. We supply around 30% of the world’s need for refined borates from our world-class mine in Boron, California, about 100 miles northeast of Los Angeles.  Learn more about Rio Tinto.

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