Potassium Pentaborate

Potassium pentaborate is a product resulting from the controlled reaction of potassium hydroxide, water and boric acid. It is a mild alkaline salt and consists of white crystalline granules.
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Applications & Benefits

Welding/soldering/brazing fluxes
In the joining of metals by silver soldering, brazing or welding, potassium pentaborate is used either alone, or in a mixture with other materials. The borate-containing flux melts and dissolves oxide impurities on the metal surfaces to be joined. It also provides a protective barrier film which prevents further oxidation. Potassium pentaborate is used in fluxes for stainless steel or various non-ferrous metals to avoid the “glare” associated with sodium borate.

Metal refining
In metal refining, borates are used as cover fluxes. Potassium pentaborate is used for refining copper and its alloys, as well as precious metals. It can provide an alternative to typical fluorine-containing flux compounds, and can help reduce fluorine emissions.

Lubricating oil additives
Potassium borates, dispersed in a very finely divided state, improve the load-carrying, anticorrosion, and antiwear properties of industrial and automotive gear lubricants. Under extreme conditions, potassium borates interact with metal load-bearing surfaces to form a film of extraordinary resilience. This tenacious film provides outstanding load-carrying capacity and wear protection.

Diazotype developer
A light-sensitive composition can be produced by combining a nonionic aromatic diazo compound and a cationic dye-borate anion complex. Potassium pentaborate can be used as the source of borate anion.

The addition of soluble borates such as potassium pentaborate inhibits the set of cement. Slowsetting cements are used in oil well drilling where they may have to be pumped to great depths before being required to harden.

Wooden and paper matches have been treated with potassium pentaborate solutions for control of the burning rate and to stop after-glow.


Senior Development Specialist

Fred Ascherl

Fred has worked for Rio Tinto Borates for over 37 years. He currently holds a position as a Senior Development Specialist.