| ADDITIVE | WHAT IT DOES | HOW IT WORKS |
| Oxidation Inhibitor | Prevents varnish and sludge formation on bearings or in circulating systems. Retards aging of the oil. Lengthens service and storage life of oil. Protects oil itself directly (indirect protects metal parts - varnish and acids) | Reacts more readily with oxygen (from air) than does the oil itself, thereby retarding oxidation of the oil. |
| Rust Inhibitor | Prevents rusting of ferrous (iron or steel) machine parts | Forms a film on ferrous metallic parts thus protecting them from attack by water or other destructive material. |
| Corrosion Inhibitor | Prevents corrosive attack on non-ferrous metallic surfaces | Forms a film on non-ferrous metallic parts thus protecting these parts from attack by contaminants in the oil. |
| Detergent | Prevents oxidation products (sludge) which have formed in oil from sticking to metal components. May also remove deposits already formed on metallic components. Usually combined with dispersant additive | By chemical reaction, oxidation products (sludge) remain soluble in the oil and do not stick to the metal surfaces. |
| Dispersant | Keeps oxidation products separated and suspended in the oil. Retards formation of sludge | By chemical reaction, oxidation product particles are kept small enough to allow them to float in the oil. |
| Foam Inhibitor | Causes foam to dissipate more rapidly | Protects combination of small bubbles into large bubbles which in turn burst more easily. |
| Viscosity Index (V.I.) Improver | Reduces rate of change of viscosity with temperature | Additive thickens with increasing temperature thereby preventing oil from thinning out too rapidly |
| Pour Depressant | Lowers the Pour Point | Keeps small wax crystals apart thus preventing the formation of large crystals which would stop the flow of oil. |
| Antiwear agent | Minimizes wear caused by metal-to-metal contact during conditions of mild boundary lubrication e.g. starts and stops | Additive reacts chemically and forms a film on metal surfaces under normal operating conditions |
| Extreme Pressure (E.P.) Agent | Prevents welding and subsequent wear or seizure of contacting metal parts under extreme or shock load conditions. | When metal-to-metal contact occurs (as under extreme or shock load conditions), the heat generated at the point of contact causes the additive to react chemically with the metal. The new compound formed between the metal surfaces reduces friction and prevents welding or seizure. |
| Tackiness Agent | Increases the adhesive properties of a lubricant - improves retention and prevents dripping and spattering | High molecular weight compounds are added to the oil thereby increasing its viscosity and improving its adhesive properties. |
| Emulsifier | Promotes rapid mixing of water and oil resulting in the formation of a stable emulsion (e.g. water-soluble cutting oils) | Reduces interfacial tension and permits intimate mixing of oil and water. |
| Fillers for Greases Molybdenum disulphide (Moly-Sulfide) Zinc Oxide | Imparts load-carrying and anti-wear characteristics to a grease. Imparts some load-carrying characteristics. Gives a white color to the grease | Unique laminar structure sticks to metal parts Fine white powder mixes readily with grease |
22. Which lubricants contain additives?
