Sodium Pentaborate

Sodium Pentaborate

Customized lubricator

Used primarily in oilfield drilling, sodium pentaborate provides lubrication and stabilization in wells and downhole drilling.



Oil field downhole drilling

When used in drilling fluids, sodium pentaborate can:

  • Enhance the performance of some polymer-based fluid-loss additives
  • Improve lubricating characteristics
  • Help control the pH of water-based fluids
  • Help inhibit corrosion to protect steel tubing, casing, and pipework
  • Reversibly cross-link viscosity-modifying polymers in water-based fluids, especially when drilling deviated or horizontal wells
  • Work with saltsor mono- and oligosaccharides to stabilize shale or clay strata in the reservoir formation rock

Oil well cement set retardant

Sodium pentaborate can be added to cement reinforcements that stabilize drilled well bore walls. Borates adsorb into the surfaces of cement grains, reacting with the available calcium ions to form calcium borate coatings that are a barrier to grain hydration and cement setting.

Nuclear energy

Sodium pentaborate can be used as a precursor for making isotopically enriched boron-10 materials that are necessary to ensure the safety within nuclear power stations.


Available Grade
  • Technical Granular
Chemical and Physical Properties

Molecular weight: 295.1 or (590.2)

Relative density: 1.69 at 20°C

Melting point/freezing point: >500°C

Appearance: White, crystalline solid

Solubility: Water: 7.5% at 10°C; 51.0% at 100°C

Stability: Product is stable under normal ambient temperatures: (-40°C to 40°C)

Chemical Composition (Theoretical)

Boric oxide, B2O3: 58.98%

Sodium oxide, Na2O: 10.5%

Water of crystallization, H2O: 30.52%

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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