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Calcium Hydroxide (Slaked Lime)

  • Bases
  • CAS 1305-62-0
  • IUPAC: Calcium dihydroxide

Calcium Hydroxide (Slaked Lime) (CAS 1305-62-0) appears in 1 of the 1,812 car-care products CarCareTruth tracks (as of June 2026).

Calcium hydroxide is an alkaline irritant classified H315 (skin irritation Cat 2) and H318 (serious eye damage Cat 1) at the ingredient level in many SDS formats. In the anti-seize paste matrix at 1-5% concentration, it contributes to the mixture-level H315 and H318 classifications. No carcinogen, sensitizer, or asthmagen classification.

Calcium hydroxide (CAS 1305-62-0), also known as slaked lime or hydrated lime, is the product of calcium oxide reacting with water. It is used as an alkaline buffer in calcium sulfonate-based greases and anti-seize compounds, where it maintains an alkaline pH environment that inhibits rust formation and neutralizes acidic byproducts generated during thermal cycling.

In paste anti-seize products, calcium dihydroxide is typically present at 1-5% concentration, where it contributes to the mixture-level alkaline character responsible for the H315 (skin irritation Cat 2) and H318 (serious eye damage Cat 1) GHS classifications. Despite its relatively low concentration, calcium hydroxide's pH-raising effect on contact with moisture explains the serious eye damage potential at the mixture level.

Calcium dihydroxide is distinct from calcium oxide (CaO): calcium oxide reacts exothermically with water, while calcium hydroxide is the post-reaction, stable form. Both appear in calcium sulfonate anti-seize formulations at different stages of the manufacturing process.

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 buffer and filler in calcium sulfonate greases and anti-seize compounds; provides alkaline reserve to neutralize acidic corrosion byproducts and stabilize the grease matrix

Common questions about Calcium Hydroxide (Slaked Lime)

What is Calcium Hydroxide (Slaked Lime) used for in car care?
Alkaline buffer and filler in calcium sulfonate greases and anti-seize compounds; provides alkaline reserve to neutralize acidic corrosion byproducts and stabilize the grease matrix
Is Calcium Hydroxide (Slaked Lime) a VOC?
No. Calcium Hydroxide (Slaked Lime) is not classified as a volatile organic compound (VOC).
Is Calcium Hydroxide (Slaked Lime) on California's Proposition 65 list?
No. Calcium Hydroxide (Slaked Lime) 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.