Additives
An agent added to oils, fuels, and coolants to impart specific beneficial properties to the finished products. Additives create new fluid properties, enhance properties already present and reduce the rate at which undesirable changes take place in a fluid during service. Selected additives are:
| Dispersants, | purpose: keep sludge, carbon and other deposit precursors suspended |
| Detergents | typical compounds: succinimides, neutral metallic sulfonates, phenates, polymeric detergents, amines | Basic Metal | purpose:neutralize acids, prevent corrosion | Compounds | typical compounds:overbased metallic sulfonates, phenates, carbonates | Oxidation Inhibitors | purpose:prevent or control oxidation of oil by forming oxygen-inactive compounds and / or scavenging free oxygen |
| typical compounds:zinc dialkyldithiophosphates; aromatic amines, sulfurized products, hindered phenols | Extreme Pressure (EP) Antiwear Additives | purpose:reduce wear, prevent scuffing and seizing by forming protective surface films |
| typical compounds:zinc dialkyldithiophosphates; tricresylphosphates, organic phosphates, chlorine and sulfur compounds | Viscosity Index Improvers | purpose:reduce the rate of viscosity change with temperature |
| typical compounds:polyisobutylene, methacrylate polymers, olefin copolymers- may incorporate dispersants | Rust Inhibitors | purpose:prevent the formation of rust on metal surfaces by formation of surface film or neutralization of acids |
| typical compounds:high base additives, sulfonates, phosphates, organic acids or esters, amines | Corrosion Inhibitors | purpose:prevent corrosive attack on alloy bearings or other metallic surfaces |
| typical compounds:organically active sulfur, phosphorus, nitrogen compounds such as phosphites, metal salts of thiophosphoric acid, sulfurized waxes, terpenes | Antifoamants | purpose:reduce foam with surface tension modifiers that break up large surface bubbles, or small entrained bubble reducers |
| typical compounds:silicones, organic polymers | Friction Modifiers | purpose:reduce or modify friction |
| typical compounds:long chain polar compounds, (amides, phosphates, phosphites, acids, etc.), molybdenum disulfides | Metal Deactivators | purpose:form surface films so metal surfaces do not catalyze oil oxidation |
| typical compounds:zinc dialkyldithiophosphates, metal phenates, organic nitrogen compounds | Pour Point Depressants | purpose:lower “freezing” point of oils assuring free flow at low temperatures |
| typical compounds:low molecular weight methacrylate polymers | Emulsifiers | purpose:permit water-in-oil or oil-in-water emulsions by changing interfacial tension |
| typical compounds:soaps of fatty acids, sulfonic or napthenic acids | Demulsifiers | purpose:lower emulsion stability |
| typical compounds:heavy metal soaps, alkaline earth sulfonates | Tackiness Agents | purpose:increase adhesiveness of lubricant on metal surfaces; reduce runoff |
| typical compounds:high molecular weight polymers, aluminum soaps of unsaturated fatty acids | Oiliness Agents | purpose:lower friction under near-boundary conditions |
| typical compounds: high molecular weight polar compounds such as fatty oils, oxidized waxes or soaps |