Gearbox lubricants are basically categorised into two types based on the raw materials used for the manufacture. They are Mineral based Lubricant Oils and Synthetic Based Lubricating Oils. Though they differ based on the raw materials used for manufacture, they cannot be used directly for a gearbox. They require some property enhancing additives to be added to them in order to make them work perfectly for a gearbox.
Let us look into the various such property enhancing additives that are added to the lubricants.
1. Oxidation Inhibitors: These are elements that prevent the oxidation of the lubricant, resist acidic action on the lubricants. They play a major role in preventing the oil form thickening due to the sludge formation due to continuous running for a prolonged period of time.
2. Rust Inhibitors: These are elements which make the oil to cling on to the surface of the gear, bearing keeping it wet with oil and thus preventing the surface from getting rusted.
3. Corrosion Inhibitors: These are chemical elements that prevent the reaction of the inhibitors and the oil from chemically acting on the metal surfaces and other contaminants in the lubricant. They act as neutralizing agents in majority cases.
4. Foam Inhibitors: The lubricant in the gearbox is consistently churned and agitated. It is the normal tendency of any liquid to foam up under such a situation and the gear lubricant is no exemption from this. These elements keep the lubricant from foaming excessively and contain the oil from overflowing due to foaming.
5. Dispersants: These are elements that keep the contaminants generated in the gearbox from getting together to form a sludge or solids. They help in keeping the contaminants suspended in the lubricant separately.
6. Extreme Pressure (E.P) Additives: These are elements that are chemically active oil soluble and take up the extreme pressure between two contacting surfaces of the gear teeth.
7. Anti – Wear Additives: These elements form a chemical film on the gear teeth in contact and prevent metal to metal contact. They enhance the oil film formation capability of the lubricant.
8. Oiliness Additives: These elements are basically provided to reduce friction by adhering to the metal surfaces and making them slippery.
9. Tackiness Additives: These are elements that increase the adhesiveness of the lubricant enabling them to stick on to vertical surfaces. They do come down but the time taken to do so is very high. This enables lubricating of the gears in a gearbox which have splash lubrication system.
All these elements put up together tend to form a gear lubricant with the requisite properties.