Home / Antioxiant

Phenolic · Aminic · ZDDP · Peroxide Decomposer · RPVOT

Antioxidant
Additive

Antioxidants are additives that increase the oxidative resistance of the base oil to prolong lubricant life. They help prevent or reduce lubricant oxidation and work collaboratively with other additives in finished lubricants.

Phenolic, Aminic & Synergistic Combinations

As the name suggests, antioxidants prevent oxidation; thus, it is no surprise that they are also called Oxidation inhibitors. During the refining of the base oil, the natural antioxidants are typically stripped away. Thus, additional antioxidants must be added to the finished lubricant to ensure it does not oxidize as quickly. It is important to note that antioxidants can reduce the amount of oxidation that occurs but will not stop it completely. Some of the natural antioxidants in base oils include polycyclic aromatics and sulphur and nitrogen heterocyclics6. During oxidation, acids, and peroxides are typically produced. Antioxidants added to finished lubricants usually contain hindered phenols and ZDDPs (zinc dialkyldithiophosphates). These will suppress the formation of the acids produced in these reactions. Dedicated antioxidants are amines, phenols, and sometimes ZDDP, which also function as an antiwear additive. Antioxidants account for 3-7% of European and North American diesel and gasoline additive packages for finished lubricants6.

What happens during the oxidation cycle?

Antioxidants are additives designed to prolong the life of a lubricant by increasing the oxidative resistance of the base oil. Antioxidants allow lubricants to operate at higher temperatures than would otherwise be possible without them. Many synthetic lubricants, especially hydrocarbon-based lubricating oils, are susceptible to degradation by oxygen. This oxidation process, which is initiated by the formation of reactive free radicals and peroxides, is the major cause of oil thickening and the formation of sludge and varnish in many applications.

Both are hindered phenol antioxidants. BHT (butylated hydroxytoluene, 2,6-di-tert-butyl-4-methylphenol) is a small-molecule food-grade phenol — cheap, volatile, used as commodity antioxidant in food, plastics and low-temperature lubricants. 2,6-DTBP (2,6-di-tert-butylphenol) is the lubricant-grade hindered phenol — slightly larger, less volatile, better thermal stability.

RPVOT = Rotating Pressure Vessel Oxidation Test (ASTM D2272). 50 g oil + 5 g water + Cu wire coil in a sealed pressure vessel, pressurised with O2 to 90 psi, rotated at 100 rpm in a 150 °C bath. Time to oxygen pressure drop of 175 kPa is the RPVOT life.

Used for turbine oil, hydraulic, transformer oil and gear oil oxidation life specification. ISO 32/46/68 turbine R&O target ≥ 1,000 minutes; premium turbine 2,000-3,000 min. Phenolic + aminic AO synergy is the main lever to extend RPVOT.

Hindered phenols are colourless when fresh but darken on oxidation — the oxidised quinone form is yellow / amber. High phenolic treat rate gives darker finished oil colour over time, which OEMs (especially aerospace, turbine, ATF) sometimes specify against.

Premium turbine and ATF formulations use lower phenolic and rely more on aminic + ZDDP for AO. PCMO and HDD don’t have colour specs, so phenolic can be used freely up to 1-2% treat.

Premium turbine and ATF formulations use lower phenolic and rely more on aminic + ZDDP for AO. PCMO and HDD don’t have colour specs, so phenolic can be used freely up to 1-2% treat.

1. Pour Point Depressants

2. Viscosity Index Improvers

3. ZDDP Anti-Wear Additives

4. Antioxidants

5. TBN Boosters, Detergents

6. Lubricant Additive Packages

7.Grease Raw Materials

8. Base Oils

9.Coolant & Brake Fluid Additives

10.Other Specialty Chemicals

Formulate High-Performance Lubricants with Confidence

Formulate High-Performance Lubricants with Confidence

AB Petrochem supplies carefully selected lubricant additive packages that help manufacturers streamline production while delivering consistent, high-quality performance.
Speak with Our Specialists →

Download Catalogue →