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Methylbenzotriazole (Tolyltriazole)

  • Corrosion inhibitors
  • CAS 29385-43-1
  • IUPAC: 1H-benzotriazole, 4(or 5)-methyl-

Methylbenzotriazole (Tolyltriazole) (CAS 29385-43-1) appears in 1 of the 1,812 car-care products CarCareTruth tracks (as of June 2026).

H302 (harmful if swallowed Cat 4), H361 (suspected reproductive toxin Cat 2) at the substance level. The reproductive toxicity classification is the primary concern — at <1% in a diesel treatment formulation, this typically propagates to the mixture-level SDS only when the SDS methodology uses the GHS additivity calculation rather than strict cutoff thresholds.

Methylbenzotriazole (1H-benzotriazole-4 or 5-methyl, CAS 29385-43-1, also known as tolyltriazole or TTA) is a corrosion inhibitor used in fuel additives, metalworking fluids, and engine coolants. It forms a protective film on copper, brass, and other non-ferrous metal surfaces, preventing oxidative corrosion in fuel system components. At the substance level it carries H302 (harmful if swallowed) and H361 (suspected of damaging fertility or the unborn child). At typical fuel-additive concentrations of <1%, the H361 classification may or may not propagate to the mixture level depending on the SDS author's classification methodology.

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: Metal passivator and corrosion inhibitor used in fuel additives and coolants to protect copper, brass, and other non-ferrous metal fuel system components from oxidative corrosion.

Common questions about Methylbenzotriazole (Tolyltriazole)

What is Methylbenzotriazole (Tolyltriazole) used for in car care?
Metal passivator and corrosion inhibitor used in fuel additives and coolants to protect copper, brass, and other non-ferrous metal fuel system components from oxidative corrosion.
Is Methylbenzotriazole (Tolyltriazole) a VOC?
No. Methylbenzotriazole (Tolyltriazole) is not classified as a volatile organic compound (VOC).
Is Methylbenzotriazole (Tolyltriazole) on California's Proposition 65 list?
No. Methylbenzotriazole (Tolyltriazole) 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.