Overview
High-temperature antioxidants protect lubricating oils from oxidative degradation that occurs at elevated temperatures in engine combustion zones, turbine oil systems, and high-temperature industrial applications. Oxidation leads to viscosity increase, acid formation, varnish, sludge, and corrosive deposits. Multiple antioxidant chemistries are available: thioether-phenolic esters, pure phenolic esters, ash-free N/S type compounds, and diphenylamines. Each chemistry offers different performance advantages. Phenolics excel at peroxy radical scavenging, diphenylamines provide outstanding high-temperature stability, and the ash-free N/S type is versatile across turbine, hydraulic, and engine oil applications.
| Chemistry | N or S % | Flash Point (°C) |
|---|---|---|
| Thioether and Phenolic Ester Type Antioxidant | S: 4.5–5.5 | ≥63 (MP) |
| Ester-Phenolic Antioxidant | ≥96% effective content | ≥170 |
| Ash-free Antioxidant (N/S Type) | N: 6.3–7.0; S: 26.5–32.5 | ≥170 |
| Butyl Octyl Diphenylamine | N: 4.30–5.00 | ≥180 |
| P,p′-Dinonyl Diphenylamine | N: 3.2–3.8 | ≥135 |