*2.2.1.4 Antioxidants*

Antioxidants or oxidation inhibitors prevent the oxidation of the components of the base oil there by increasing the life of the lubricant. Oxidation of the lubricant molecules occur at all temperatures but at higher temperatures, it is accelerated. The presence of wear particles, water, and other contaminants also promote Oxidation of the lubricant molecules which then leads to formation of acids and sludge. The acids may further cause corrosion in the metallic parts while the sludge formation increases the viscosity of the lubricant. Almost every lubricating oil and grease contains antioxidants and examples include Zincdialkyldithiophosphates, hindered phenols, sulphurized phenols, and aromatic amines. These compounds decompose peroxides and terminate free-radical reactions that occur in the lubricant. These are sacrificial in nature hence their quantity gets reduced with time.
