Additives - types of additives



Lubricant additives can be defined as agents that introduce new positive properties or enhance pre-existing lubricant characteristics. Natural hydrocarbons consisting of mineral oils cannot, for a long time, satisfy the ever-increasing demands placed on modern lubricants, which is why they are given artificial (synthetic) substances, collectively called additives. Some additives affect the physical properties of base oils, such as viscosity-temperature characteristics, propensity to crystallize paraffins, etc., while others have a primarily chemical effect.

The main lubricating components of motor oils are base oils, which are obtained by refining oil. In atmospheric (fractional) distillation plants, in principle, first gasoline is isolated as the easiest volatile component, then diesel fuel as medium volatile component and what remains in the end, as the most difficult volatile component, is the starting material for obtaining base oils. They are produced in four or five fractions by viscosity which approximately correspond to the viscosity numbers SAE 10, 20, 30, 40 and 50.

Different sources of petroleum have different types of petroleum as hydrocarbon compounds. The best base oils are obtained from paraffin oils. However, whatever the quality, such oils cannot be directly used in internal combustion engines (and not only in them), but must be subjected to further processing and refinement.

In order to obtain the required quality (quality level of engine oils), certain additives are added to the base oils which do not essentially have lubricant properties, but which allow the base oils to become good lubricants, which will meet all the requirements defined by certain standards and so-called. specifications. Today, up to 20 percent of additives are added to one engine oil, while the remaining 80 percent is base oil. According to the most general functions, additives are divided into three groups: additives for the protection of metal surfaces, additives for improving the performance of lubricating oils and additives for protecting the lubricating oils themselves.

Additives for protecting metal surfaces serve to protect engine parts from wear, to prevent rust and corrosion, to keep engine parts clean, to prevent the formation of large particles in sediments, to prevent the formation of "hot" and "cold" deposits, as well as the formation of lacquers on the piston liner and finally , to improve the friction situation in conditions close to boundary lubrication.

Additives for improving the performance of lubricating oils have the task of improving the oil fluidity at low temperatures, reducing the change in oil viscosity as the temperature changes, and causing the seals to swell, ensuring the tightness of the coupling of the coupled engine parts.

Lubricating oil protection additives they have a role to play in preventing the formation of foam in the oil during engine operation, to slow down the aging of engine oil caused by oxidation phenomena, and to prevent the catalytic action of metal particles on the oxidation of oil.

It is quite clear that there are a large number of additives that are added to the base oils in order to obtain the final product of maximum quality. We will try to present them individually.

Viscosity index additives

These additives carry important viscometric characteristics of multi-engine oils, which can be summarized as follows: at low temperatures it is necessary to provide oil flow, at high temperatures oil of a certain viscosity is required to ensure a sufficient thickness of the oil layer and at the same time its low consumption even at high pressures require oil that provides a certain thickness of the oil layer.

Additives for lowering the flow point

These are the additives that lower the minimum temperature at which the oil exhibits a flowing property. Some special oils require a particularly low flow point, which is achieved by the process of deep deparaffining. As this is a very expensive process, it is carried out to a temperature of –8 ° C to –18 ° C. Further lowering of the flow point is achieved by adding additives for lowering the flow point.

Additives to improve load resistance

As the load between the two sliding surfaces separated by oil increases, speed and viscosity decrease, the thickness of the oil layer gradually decreases to the critical limit, where the law of hydrodynamic lubrication ceases to apply. This results in tearing of the oil layer and contact of the tops of the surface unevenness, which results in dry friction. This group includes polar additives, anti-wear additives and EP additives (for high pressures).

Detergent additives

Today it is not possible to produce modern engine oil without the use of detergents and dispersants. This type of additive is intended to prevent the formation of deposits on metal surfaces, to neutralize acidic combustion products and to protect the metal from corrosive wear.

Dispersant additives

Although they represent a special group of additives, there is essentially no sharp distinction between dispersive and detergent action. The ultimate goal of dispersant activity is the property of maintaining the dispersion ("dissolved") of all that does not belong to the lubricating oil, whether originating outside the oil or the product of thermal-oxidative aging of the oil. Here is an example; a product that is certainly foreign to oil is water, and this type of additive does not allow it to be extracted from the entire volume of the oil.

Corrosion and rust additives

The goal of corrosion protection is to prevent oxygen or other aggressive substances and moisture from entering the metal surface.

Rust additives are defined as compounds that are capable (alone or dissolved in oil) of protecting a surface exposed to water, the presence of oxygen, and the time interval necessary to cause a phenomenon known as rust.

Additives Emulsifiers

Emulsions basically consist of three components: oil, water and emulsifier and as such are mostly used in operations of mechanical processing of metal, during its cooling. The task of the emulsifier is to create conditions under which one component (water) will dissolve in another (oil) or vice versa, although this would not be possible under normal circumstances.

Anti-foaming additives

The formation of foam in lubricating oils during their exploitation can cause lubrication interruption, increased consumption and higher speed of oxidation of the lubricant.

Other additives

Other additives used in the petrochemical industry include de-emulsifiers, drip additives, bactericides, odorants and coloring additives.

From what has been presented so far, it is important to emphasize the following; it may be that the additives of one manufacturer do not "stand up" with the additives of another, which can result in serious changes in the mixed oils of the two engine oil manufacturers, which would inevitably affect the engine itself. For this reason, it is considered undesirable to fill the engine of another manufacturer with the engine that is already in the engine

Prepared by: Dušan Ković
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