Borax

Borax (CAS 1303-96-4) is an inorganic sodium borate salt used in industrial and consumer formulations. Also marketed as E285 in food contact and preservation applications.

Where is Borax used?

• Cleaning and surface treatment: pH buffer, corrosion inhibitor and processing aid
• Metalworking and industrial lubricants: corrosion inhibitor and anti-wear additive in cutting fluids
• Coatings and adhesives: crosslinking agent for polyvinyl alcohol-based systems
• Textile and leather processing: flame retardant treatment and pH regulator during fiber preparation and tanning
• Personal care and cleaning formulations: buffering agent and mild preservative booster
• It serves as a pH buffer and multifunctional processing aid.
• In the glass and ceramics sector, it can be used as a raw material that supports melting behavior and can affect surface properties and durability.
• Used in soldering and processing of metals, where it reduces and cleans metal oxides.
• In cleaning formulations, borax decahydrate acts as an enzyme stabilizer.
• Borax decahydrate emulsifies oils, waxes, and paraffins.

Formulation notes

• Borax is an alkaline boron compound, whereas boric acid is a weak acid boron source.

Typical specification

• The B2O3 content of borax pentahydrate is 47.8–49%.
• Disodium tetraborate pentahydrate has CAS number 12179-04-3.
• Borax decahydrate is available in white crystalline powder or granular form.
• The name borax is usually reserved for disodium tetraborate decahydrate, while anhydrous borax and borax pentahydrate designate the other industrially used forms.

Regulatory status

• The specific concentration limit for borax was removed by Commission Delegated Regulation (EU) 2021/849, so the generic concentration limit of 0.3% for Repr. 1B substances applies from 17 December 2022.
• Borax is included in REACH Annex XVII entry 30 appendix 6 and cannot be placed on the market or used by the general public at concentrations of 0.3% or more, with packaging labelled 'Reserved for professional users'.
• Borax (disodium tetraborate decahydrate, CAS 1303-96-4) is no longer authorised as a PT08 wood preservative biocide in the EU since 31 August 2021.
• Borax (disodium tetraborate decahydrate) is classified as toxic for reproduction, category 1B, under CLP.

Frequently asked questions about Borax

What are the applications of borax in paper production?

Borax is used in paper production to increase paper durability and improve pulp quality.

How does borax function in welding, brazing, and soldering?

Borax decahydrate excludes air and prevents oxidation in welding, brazing, and soldering.

What is the role of borax in metal surface treatment?

Borax decahydrate neutralizes acidic residue from ethylene glycol decomposition and minimizes oxidation at metal surfaces.

Technical content is compiled and updated by the SoleChem product team from public technical sources; the certificate of analysis (COA) governs product-specific specifications.