Introduction to Common Lubricant Additives

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1. What is an antifoam agent? When internal combustion engine oils and industrial oils are used in devices such as engines, they often need to be sprayed in a mist form. This causes some air to mix into the lubricating oil, forming relatively stable bubbles that flow into the crankcase and the oil tank, thereby preventing the engine from operating properly. By adding an antifoam agent, the foam formed between the lubricating oil and air can be broken down, the stability of the foam membrane is reduced, and the duration of the foam’s existence is shortened, thereby ensuring the proper operation of the equipment. Common antifoam agents include methyl silicone oil, acrylate and ether copolymers, etc. The unified symbol for antifoam agents is: “T9XX”. 2. What is a anticoagulant? Lubricating oils generally contain a small amount of paraffin; when the temperature of the oil drops to a certain level, paraffin crystallizes and precipitates, causing the oil to lose its fluidity and solidify. The main function of antifreeze agents is to lower the freezing point of oils. Antifreeze agents are chemically synthesized polymers or condensation products whose molecules generally contain polar groups and alkyl chains similar in structure to paraffin hydrocarbons. By adsorbing onto the surface of wax crystals or reacting with them in a eutectic manner, these agents alter the shape and size of the wax crystals, preventing the wax particles from bonding together to form three-dimensional network structures, thereby maintaining the fluidity of the oil at low temperatures. However, if the paraffin content in the lubricating oil is too high, **exceeding the capacity of the antidegradant to have an effect, then adding an antidegradant will not achieve a antidegrading effect. The antifreeze agents used in our country include alkyl naphthalene, poly-alpha-olefins, polyacrylates, etc. The unified symbol for antifreeze agents is: “T8XX”. 3. What is an anti-rust agent? Rust inhibitors can form a strong adsorption film on the metal surface, thereby preventing oxygen and water – especially water – from coming into contact with the metal surface, thus stopping rust formation. The molecular structure of the rust inhibitor should have sufficient adsorption capacity for metals, as well as good solubility in oil. Commonly used rust inhibitors include: allyl succinate, heptadecylimidazolyl allyl succinate, zinc naphthenate, barium dinonylnaphthalenesulfonate, benzotriazole, and barium petroleum sulfonate. The unified symbol for rust inhibitors is: “T7XX”. 4. What are antioxidants and metal deactivators? During use, in the presence of oxygen and under the influence of heat, light, and metal catalysis, the weakest carbon-hydrogen bonds in the lubricant molecules are broken, triggering a chain reaction of free radicals that results in the formation of oxides, peroxides, water, and other substances. Subsequently, further polymerization and condensation occur, resulting in the formation of gums, sludge, paint films, etc., which degrade the performance of the lubricant and shorten its service life. The function of antioxidants is to inhibit the oxidation of oils, deactivate the catalytic effect of metals, reduce the deterioration of oils, and extend their service life. It is mainly used in turbine oils, industrial gear oils, anti-wear hydraulic oils, transformer oils, and general machine tool oils. Domestic antioxidants and metal deactivators include 2,6-di-tert-butyl-p-cresol, N-phenyl α-naphthylamine, benzotriazole derivatives, thiadiazole derivatives, etc. The unified symbol for antioxidants and metal deactivators is: “T5XX”. 5. What is a viscosity index improver? Viscosity index improvers, also known as viscosity enhancers, are oil-soluble chain-like polymer molecules with molecular weights ranging from tens of thousands to several million. They exhibit different forms at various temperatures and have varying effects on viscosity; they increase viscosity and improve wetting properties, that is, they possess a high viscosity index. Viscosity index improvers are mainly used to formulate multi-grade diesel engine oils, and secondly to formulate hydraulic oils and hydrodynamic transmission fluids with good low-temperature performance. The main viscosity index improvers in our country include polyethylene n-butyl ether, polyacrylate, polyisobutylene, ethylene-propylene copolymer, etc. The unified symbol for viscosity index improvers is: “T6XX”. 6. What are oiling agents and friction modifiers? Any additive that enables the lubricant to form a directed adsorption film on the friction surfaces, thereby improving friction properties and reducing friction and wear between moving parts, is referred to as an oiliness agent or a friction modifier. Common oily agents include: sulfided whale oil, sulfided cottonseed oil, dimeric acids, ethylene glycol oleate, sulfided olefinic cottonseed oil, benzotriazole fatty acid amine salts, phosphonates, etc. Unified symbol for oiling agents and friction modifiers: “T4XX”. 7. What is an extreme pressure anti-wear agent? Extreme pressure anti-wear agents are primarily organic polar compounds containing sulfur, phosphorus, and chlorine. These compounds can form a relatively strong compound film on the metal surface under high pressures; this film has a melting point lower than that of the metal. When the temperature rises due to friction and pressure at the contact points between metals, this compound film melts, creating a smooth surface that reduces friction and wear on the metal surface. The types of extreme pressure anti-wear agents include organic chlorides, organic sulfides, organic phosphides, organic metal salts, etc. The unified symbol for extreme pressure anti-wear agents is “T3XX”. 8. What are antioxidant and antirust agents? Antioxidant and anti-corrosion additives possess antioxidant and anti-corrosive properties as well as anti-wear effects; they are primarily used in diesel engine oils, and to a lesser extent in industrial lubricants such as gear oils and hydraulic oils. The function of antioxidant and anti-corrosion agents is to inhibit the oxidation process of lubricating oils, deactivate the catalytic effect of metals, reduce the oxidative degradation of the oil, thereby extending its service life; at the same time, they protect the metal surfaces of mechanical components from corrosion by acids. Among petroleum product additives, antioxidants and antirust agents rank third in production, behind detergents and viscosity index improvers. Domestic antioxidant and anticorrosive agents include zinc sulfophenolate, zinc dialkyldithiophosphate (abbreviated as ZDDP), etc. The unified symbol for antioxidant and antirust agents is “T2XX”. 9. What are the types of quiet dispersants? Detergents and dispersants can be collectively referred to as detergency dispersants, and they are the most widely used type of additive in engine lubricants. Based on the type of their compounds, they are classified as: petroleum carbonates, synthetic sulfonates, thiophosphopolyisobutylene salts, alkyl salicylates, naphthenates, alkenyl succinimides, and sulfated alkylphenols. The unified symbol for the quiet dispersant is “T1XX”.