Composition and Functionality of Additive Compounds
Additive compounds can be classified into various functional categories, according to their purpose of use. The most commonly used additives include:
Anti-oxidants: They protect the lubricant from being oxidized by oxygen or other reactive substances, which can lead to viscosity increase, acidity formation, and varnish buildup.
Anti-wear agents: They help reduce friction between moving parts and minimize metal-to-metal contact, wear, and scuffing under high-pressure conditions.
Friction modifiers: They can adjust the friction coefficient between two surfaces and reduce energy loss due to frictional heating.
Extreme pressure (EP) additives: They form a protective film on the metal surface, preventing the metal-to-metal contact from occurring under high-load and low-speed conditions.
Detergents and dispersants: They clean out carbonaceous deposits and remove harmful contaminants, such as dirt, dust, sludge, and acid, from the engine components.
Foam inhibitors: They break down surface tension forces and prevent air bubbles from forming and accumulating inside the lubricant, which can cause cavitation and mechanical damage.
Corrosion and rust inhibitors: They form a protective layer on the metal surface and protect it from being corroded or rusted due to water or acidic substances.
Pour point depressants: They lower the temperature at which the lubricant becomes too viscous and loses its fluidity, which can affect the start-up performance of the engine.
Viscosity index improvers: They improve the viscosity-temperature behavior of the lubricant by reducing the viscosity change in response to temperature fluctuations.
Overall, lubricating oil additives play a vital role in enhancing the performance of lubricants and extending the lifespan of mechanical equipment. By selecting the appropriate additives and their concentration levels, it is possible to customize the formulation of the lubricant to meet the specific requirements of different types of engines, operating conditions, and environmental factors.