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Calcium Oxide (Quicklime)

  • Bases
  • CAS 1305-78-8
  • IUPAC: Calcium oxide

Calcium Oxide (Quicklime) (CAS 1305-78-8) appears in 1 of the 1,812 car-care products CarCareTruth tracks (as of June 2026).

Calcium oxide is an alkaline irritant. At ingredient level it is classified as corrosive (H314, H318 at pure substance). At mixture level in anti-seize paste (10-30% in a petroleum-grease matrix), the mixture classifies H318 (serious eye damage Cat 1) and H315 (skin irritation Cat 2). The primary hazard is eye contact — eye protection is required per H318 at mixture level.

Calcium oxide (CAS 1305-78-8), also known as quicklime, is an inorganic alkaline filler used in calcium sulfonate-based anti-seize compounds and industrial greases. In the grease matrix, it contributes alkaline buffering capacity that helps neutralize acidic byproducts from petroleum oxidation during high-temperature service, extending the effective life of the lubricant.

At pure substance level, calcium oxide is aggressively alkaline and classified as a skin/eye corrosive. In paste anti-seize at 10-30% concentration within a petroleum-grease matrix, the mixture-level GHS classification is H318 (serious eye damage Cat 1) and H315 (skin irritation Cat 2) — the corrosive character is moderated by dilution but the serious eye damage classification remains. Safety goggles are warranted for any product containing this ingredient at these concentrations.

Calcium oxide reacts exothermically with water and is incompatible with strong acids. In service on fastener threads, it contributes to the alkaline reserve without presenting an environmental concern under normal automotive 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
5/5
Purpose: Alkaline filler and anti-corrosion agent in calcium sulfonate-based anti-seize compounds and greases; contributes alkaline reserve that neutralizes acidic corrosion byproducts

Common questions about Calcium Oxide (Quicklime)

What is Calcium Oxide (Quicklime) used for in car care?
Alkaline filler and anti-corrosion agent in calcium sulfonate-based anti-seize compounds and greases; contributes alkaline reserve that neutralizes acidic corrosion byproducts
Is Calcium Oxide (Quicklime) a VOC?
No. Calcium Oxide (Quicklime) is not classified as a volatile organic compound (VOC).
Is Calcium Oxide (Quicklime) on California's Proposition 65 list?
No. Calcium Oxide (Quicklime) is not on California's Proposition 65 list.

1 product contain this

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.