Sodium Tetraborate (Borax)
- Corrosion inhibitors
- CAS 1330-43-4
- IUPAC: Disodium tetraborate
CarCareTruth tracks Sodium Tetraborate (Borax) (CAS 1330-43-4) as a car-care ingredient.
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
Common questions about Sodium Tetraborate (Borax)
- What is Sodium Tetraborate (Borax) used for in car care?
- Corrosion inhibitor in HOAT coolant formulations; protects ferrous metals and solder alloys
- Is Sodium Tetraborate (Borax) a VOC?
- No. Sodium Tetraborate (Borax) is not classified as a volatile organic compound (VOC).
- Is Sodium Tetraborate (Borax) on California's Proposition 65 list?
- No. Sodium Tetraborate (Borax) is not on California's Proposition 65 list.
No products on file contain this (yet)
Related
Health and environment notes translate the manufacturer Safety Data Sheet, the GHS classification, and authoritative regulatory listings (California Prop 65, EPA). Not medical advice. They describe the ingredient itself; whether a hazard applies to a finished product depends on its concentration and how it's used.