Lubricants generally consist of two parts: base oil and additives. Base oil is the primary component of lubricants and determines their basic properties. Additives complement and improve the properties of the base oil, imparting new properties and becoming an essential component of lubricants. So, what are lubricant additives?
Lubricant additives are one or more compounds added to lubricants to impart new properties or improve existing properties.
Lubricant additives can be categorized by their function as detergents and dispersants, antioxidants and anticorrosion agents, extreme pressure and antiwear agents, oiliness enhancers, viscosity index improvers, rust inhibitors, pour point depressants, and antifoaming agents.
1. Detergents and Dispersants
Detergents and dispersants include detergents and dispersants and are primarily used in internal combustion engine oils. Their primary function is to maintain engine internal cleanliness and to maintain a colloidal suspension of insoluble matter, preventing further carbon deposits or sludge formation.
2. Antioxidants and Anticorrosion Agents
Antioxidants and anticorrosion agents inhibit oil oxidation and improve its oxidative stability. They are primarily used in industrial lubricants, internal combustion engines, and process oils.
3. Extreme Pressure Antiwear Agents
The decomposition products of extreme pressure antiwear agents under high friction temperatures react with metals to form compounds with lower melting points than pure metals. This prevents seizure and welding on contact surfaces, effectively protecting metal surfaces. They are primarily used in lubricants requiring extreme pressure, such as industrial gear oils, hydraulic oils, guideway oils, and cutting oils, to enhance their extreme pressure and antiwear properties.
4. Oiliness Agents
Oiliness agents are surfactants with a polar group on one end and an oil-soluble hydrocarbon group on the other. They have a strong affinity for metal surfaces and adsorb firmly to them, forming a protective film similar to a cushion between the metals, preventing direct contact and reducing friction and wear.
5. Viscosity Index Improvers
Also known as thickeners, these agents not only increase the viscosity of the oil but also improve its viscosity-temperature performance.
6. Rust Inhibitor
It forms a strong adsorption film on metal surfaces, inhibiting the contact of oxygen and water on the metal surface, thus preventing the metal from rusting.