What are the anti-wear additives in hydraulic oil?

Anti-wear additives are commonly used in hydraulic fluids to protect metal surfaces from wear and extend the life of equipment. The function of these additives is to form a protective film on the metal surface, reducing friction and preventing metal-to-metal contact.

Some common anti-wear additives in hydraulic fluids include:

1. Zinc dialkyldithiophosphate (ZDDP):
   • ZDDP is one of the most widely used anti-wear additives in lubricating oils. It forms a sacrificial film on the metal surface that prevents wear and reduces friction.
   • Most widely used anti-wear additive in hydraulic oils.
   • Forms a film on metal surfaces, protecting against wear under high pressure and boundary lubrication conditions.
   • Can degrade over time and contribute to sludge formation.
   • Environmental concerns due to high zinc content.
2. Ashless dialkyl dithiophosphate (ADDP): ADDP is a variant of ZDDP that does not contain phosphorus and sulfur. It provides similar anti-wear and friction-reducing properties without negative effects such as the formation of ash deposits.
3. Antiwear (AW) and antiscuff (AS) agents: These additives, such as organic esters or fatty acids, improve the lubricity of the oil and provide an additional layer of protection against wear.
4. Polymers: Certain polymers, such as polyesters or copolymers, can act as anti-wear additives by increasing oil film strength and reducing friction between surfaces.
5. Metal sulfonates: Certain metal sulfonates, such as calcium sulfonate or magnesium sulfonate, can provide anti-wear and corrosion protection in hydraulic oils.
6. Molybdenum Disulfide (MoS2):
   • Solid lubricant, providing excellent high-temperature and pressure resistance.
   • Not readily soluble in oil, requiring special formulation techniques.
   • Can clog filters if not properly dispersed.
7. Phosphoric Esters:
   • Offer good anti-wear and anti-oxidation properties.
   • More thermally stable than ZDDPs, extending oil life.
   • Can be expensive compared to other options.
8. Organic Friction Modifiers (OFMs):
   • Reduce friction by physically adsorbing to metal surfaces.
   • Effective at lowering friction, potentially improving efficiency.
   • May interfere with other additives and have limited high-pressure protection.
9. Synergistic Blends:
   • Combinations of different anti-wear additives, leveraging their combined strengths.
   • Can offer broader protection and optimize performance for specific applications.
   • Formulation complexity and cost can be higher.

It is important to note that the selection and concentration of anti-wear additives in hydraulic fluids may vary based on specific equipment requirements, operating conditions and specifications provided by the equipment manufacturer.

Synergistic Blends:

• Combinations of different anti-wear additives, leveraging their combined strengths.
• Can offer broader protection and optimize performance for specific applications.
• Formulation complexity and cost can be higher.

Remember, consulting with a lubrication specialist can help you select the optimal anti-wear additives for your specific hydraulic system and operating conditions.