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CarCareTruthProducts · Ranked

Zinc Phosphate

  • Corrosion inhibitors
  • CAS 7779-90-0
  • IUPAC: Zinc phosphate

Zinc Phosphate (CAS 7779-90-0) appears in 1 of the 1,812 car-care products CarCareTruth tracks (as of June 2026).

Skin and eye irritant at substance level (H302 harmful if swallowed, H318 serious eye damage at high concentration). At 0.1–1% in a solvent-based aerosol formulation, dermal and inhalation exposure is low. The active corrosion-conversion chemistry takes place on the iron oxide surface; residual unreacted zinc phosphate in the cured film is minimal. SARA 313 reportable.

Zinc phosphate (CAS 7779-90-0) is the active rust-converting agent in Rust-Oleum Rust Reformer and similar zinc phosphate-based aerosol rust converters. Unlike phosphoric acid-based converters that work through acid attack, zinc phosphate acts as an anodic inhibitor — it reacts with ferrous ions at the metal surface to form an insoluble protective layer that interrupts the electrochemical corrosion cycle.

At 0.1–1% concentration in the aerosol formulation, zinc phosphate is present at a low level; the carrier solvents (acetone, n-butyl acetate) are the dominant ingredient classes by volume. The cured iron phosphate conversion layer has good adhesion to both bare metal and rusty surfaces, providing a paintable substrate for oil-based topcoats.

SARA Section 313 reportable compound. Zinc compounds are classified for aquatic toxicity at substance level; in a cured automotive coating, bioavailability is substantially reduced.

Health & environment profile

VOC
no
Prop 65 listed
no
Asthmagen
no
EPA Safer Choice
no
Aquatic toxicity
yes
Biodegradable
no
Bioaccumulative
no
Persistent
yes
Ozone depleting
no
Microplastic
no
PFAS
no
Env. score
5/5
Purpose: Active rust converter — reacts with iron oxide (rust) on metal surfaces to form a stable iron phosphate complex that halts the corrosion reaction

Common questions about Zinc Phosphate

What is Zinc Phosphate used for in car care?
Active rust converter — reacts with iron oxide (rust) on metal surfaces to form a stable iron phosphate complex that halts the corrosion reaction
Is Zinc Phosphate a VOC?
No. Zinc Phosphate is not classified as a volatile organic compound (VOC).
Is Zinc Phosphate on California's Proposition 65 list?
No. Zinc Phosphate 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.