Do you know these ten additives in hydraulic oil?

November 26, 2023

Do you know these ten additives in hydraulic oil?

With the development of hydraulic technology, the requirements for hydraulic oil are getting higher and higher, and the performance of the basic oil itself can not meet the requirements of the hydraulic system, and the performance of the basic oil must be improved by adding various additives. At present, almost all hydraulic oils used in hydraulic systems contain additives with various functions.

Hydraulic oil additives are roughly divided into two categories: one is to improve the physical properties of the oil additives, such as oil agent, anti-wear agent, viscosifier, anti-foam agent and decoagulant. The other is to improve the chemical properties of oil additives, such as antioxidants, anti-rust agents, anti-mold agents, demulsifier and metal passivation agents.

1. Oil agent

Oily agent is a highly polar substance, at a lower temperature and pressure, it can adsorb the metal surface to form a firm adsorption film, prevent direct contact between metal and metal, improve the strength of the oil film, and reduce the friction and wear of the metal.

In hydraulic oil, commonly used oil agents are: oleic acid, vulcanized whale oil (T401), vulcanized cottonseed oil (T404), vulcanized olefin cottonseed oil (T405), dimeric acid (T402) and so on.

2. Anti-wear agent

At high friction temperature, the decomposition products of the antiwear agent react with the metal surface to produce a compound film with low shear stress and low melting point to prevent the bite or welding of the contact surface, resulting in plastic deformation to fill the uneven part between the friction surface, so that the contact surface increases, the pressure decreases, and the wear decreases.

In antiwear agents, sulfur, phosphorus and chlorine are usually contained, and their compounds have their own characteristics. Antiwear agent containing sulfur, under high temperature friction conditions, sulfide reacts with iron to form iron sulfide film, which plays an antiwear role; The anti-wear agent containing phosphorus interacts with steel by the product of thermal decomposition of phosphate ester at not too high temperature and moderate friction conditions. Generate low melting point, high plasticity of phosphate mixture, so as to play an anti-wear role; Under extreme pressure conditions, the antiwear agent containing chlorine produces ferric chloride film, which has a layered structure, small friction coefficient, easy shear and good lubrication effect.

In hydraulic oil, commonly used anti-wear agents are: dialkylzinc dithiophosphate (T203), trit306 (T306), thiophosphate (T303), sulfurized olefin (T321), chlorinated paraffin (T301) and so on.

3. Tackifier

Viscosifier is a kind of additive to improve the viscosity temperature of hydraulic oil and increase the viscosity index. This is a kind of high polymer, at low temperature, in the oil shrinkage and curl into a tight small ball, low temperature viscosity has little impact, high temperature, swelling and stretching in the oil, increase viscosity, can improve the viscose-temperature characteristics.

In hydraulic oil, commonly used viscosifiers are: polyn-butyl vinyl ether (T601), polyisobutylene (T603), ethylene-propylene copolymer (T611), polymethacrylate (KT8602) and so on.

4. Anti-foam agent

Anti-foam agent is a kind of substance that can reduce the stability of foam adsorption film and shorten the existence time of foam. Adding anti-foam additives in hydraulic oil can reduce the surface tension and make the bubbles overflow the oil surface quickly, so as to eliminate bubbles.

In hydraulic oil, commonly used anti-foam agents are: dimethylsilicone oil (T901), polyester non-silicon anti-foam agent (T911), metal soap, fatty acids and so on.

5. Anticoagulant

Coagulant is a kind of additive which can inhibit the formation of network crystallization of paraffin in oil, reduce the freezing point and maintain the fluidity of oil. By means of adsorption or eutectic formation on the paraffin crystal surface, the agent changes the crystal shape and size of the paraffin to reduce the condensation point of the oil.

In hydraulic oil, commonly used point reducing agents are: alkyl naphthalene (T801), polymethacrylate (T602B),α olefin copolymer (M), ethylene vinyl acetate polymer (T804) and so on.

6. Antioxidants

Antioxidants are a kind of additives that are easily oxidized themselves and can generate compound films on the surface of metals, isolate contact with oxygen and other corrosive substances, and prevent the catalytic effect of metal oxidation on oil and the corrosion effect of oil on metal.

Generally, several antioxidant additives are used in combination, and the antioxidant effect is better, such as the compound of sulfide and aromatic hydrocarbons, which will produce synergistic effect; The compound of free radical terminator and peroxide decomposing agent also has obvious synergistic effect.

In hydraulic oil, commonly used antioxidants are :2, 6-di-tert-butyl-p-cresol (T501), n-phenyl-alpha naphthylamine (T531), isobutylene sulfide (T321), dialkyl dithiocarbamate, aromatic hydrocarbons, bisphenol and so on.

7. Rust inhibitor

Rust inhibitor is a class of polar compounds, which can form a strong water-enhancing adsorption film on the surface of the metal to prevent the metal from rusting.

In hydraulic oil, the commonly used anti-rust agents are: dodecenyl succinic acid (T746), barium dinonylnaphthalene sulfonate (T705), dodecenyl succinate of heptadenyl imidazoline (T703) and so on.

8. Anti-mold agent

Anti-mildew agent can prevent and inhibit mildew in emulsified oil.

In hydraulic oil, commonly used anti-mold agents are: phenolic compounds, formaldehyde compounds.

9. Deemulsifier

Demulsifier is a kind of substance that can make water and oil separate or settle out well.

In hydraulic oil, commonly used demulsifier are: polyether polymer compounds and various ethylene oxide, propylene oxide polymer.

10. Metal passivator

Metal passivator is a kind of additive that can protect non-ferrous metals, especially copper surface corrosion. It can also increase the oxidation resistance of oil products and inhibit and passivate the corrosion of copper by acidic substances.

There are two types of metal passivating agents used in hydraulic oil: one is film forming passivating agents, which can form a coating with the surface of copper to prevent the erosion of acids, active sulfides and corrosive extreme pressure agents. Commonly used are benzotriazole (T706), and another class is active sulfur scavengers, which react with active sulfides to produce low-corrosive or non-corrosive polysulfur compounds.

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