Tannins
- Acids
- CAS 1401-55-4
- IUPAC: Polyphenolic compounds (gallic acid derivatives)
Tannins (CAS 1401-55-4) appears in 1 of the 1,812 car-care products CarCareTruth tracks (as of June 2026). It is readily biodegradable.
Natural polyphenols at 1–5% concentration in rust converter formulas. Not classified as a skin irritant, eye irritant, or inhalation hazard at mixture-use concentrations.
Tannins (gallic acid derivatives, CAS 1401-55-4) are naturally occurring plant polyphenols found in bark, nutgalls, and other plant material. In rust converter products, tannins react with iron oxide on a metal surface to form ferric tannate — a dark, relatively stable compound that provides a barrier against further oxidation. This conversion chemistry is the basis for the "tannic acid-based" rust converter category, which is generally considered less chemically aggressive than phosphoric acid-based alternatives.
Tannins have moderate aquatic toxicity at ingredient level (fish LC50 approximately 37 mg/L in Gambusia affinis, EC50 29 mg/L for aquatic molluscs — corresponding to GHS acute aquatic Category 3). They are plant-derived and considered biodegradable. They are not classified under Prop 65, not known asthmagens, and not VOC components.
Health & environment profile
- VOC
- no
- Prop 65 listed
- no
- Asthmagen
- no
- EPA Safer Choice
- no
- Aquatic toxicity
- yes
- Biodegradable
- yes
- Bioaccumulative
- no
- Persistent
- no
- Ozone depleting
- no
- Microplastic
- no
- PFAS
- no
- Env. score
- 3/5
Common questions about Tannins
- What is Tannins used for in car care?
- Active rust-conversion agent — reacts with iron oxide (rust) to form ferric tannate, a stable dark protective compound
- Is Tannins a VOC?
- No. Tannins is not classified as a volatile organic compound (VOC).
- Is Tannins on California's Proposition 65 list?
- No. Tannins is not on California's Proposition 65 list.
- Is Tannins biodegradable?
- Yes. Tannins has a confirmed biodegradable profile.
1 product contain this
FDC Rust Converter ULTRA (1 Gallon)Prop 65rust-converter
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.