Sodium Tetraborate (Borax)
- Corrosion inhibitors
- CAS 1330-43-4
- IUPAC: Disodium tetraborate
ACGIH TLV 2 mg/m³ TWA for respirable fraction (inhalation, not relevant to coolant pour-fill use). LD50 oral rat 1,200 mg/kg. Present at 1.5–5% in consumer coolant — no H-code classification at these concentrations.
Sodium tetraborate (borax, Na₂B₄O₇) is a mineral salt used as a corrosion inhibitor in automotive coolant formulations, particularly HOAT (Hybrid Organic Acid Technology) systems. It provides buffer capacity and inhibits corrosion of ferrous metals and solder connections in the cooling system.
At the concentrations used in consumer antifreeze products (1.5–5%), sodium tetraborate does not carry a GHS hazard classification at the mixture level. Industrial handling of anhydrous borax powder carries inhalation exposure limits (ACGIH TLV 2 mg/m³ respirable fraction) that are irrelevant to consumer liquid coolant use. The borax in coolant is fully dissolved in aqueous solution and presents no dust inhalation pathway during normal pour-fill use.
Health & environment profile
- VOC
- no
- Prop 65 listed
- no
- Asthmagen
- no
- EPA Safer Choice
- no
- Aquatic toxicity
- no
- Biodegradable
- no
- Bioaccumulative
- no
- Persistent
- no
- Ozone depleting
- no
- Microplastic
- no
- PFAS
- no
- Env. score
- 3/5
No products on file contain this (yet)
Health summaries are editorial — we synthesize from SDSs, peer-reviewed sources, and regulatory listings. Not medical advice.