Lubrication professionals are usually very familiar with the base oil viscosity of their lubricants. After all, viscosity is the most important characteristic of base oils.
Set the baseline of the oil intake and monitor the health of the lubricant based only on the viscosity. However, lubricants are more than just viscosity. It is important to understand the role of additives and their function in lubricants.
Lubricating oil additives are organic or inorganic compounds dissolved or suspended in oil in solid form. They are usually between 0.1% and 30% of the oil volume, depending on the machine.
Additives have three basic functions:
Use antioxidants, corrosion inhibitors, defoamers and demulsifiers to enhance the characteristics of existing base oils.
Use pour point depressants and viscosity index (VI) improvers to suppress poor base oil properties.
Use extreme pressure (EP) additives, cleaners, metal passivators and adhesives to give new characteristics to the base oil.
Additive polarity is defined as the natural directional attraction of additive molecules to other polar materials in contact with oil. Simply put, it is anything that dissolves or dissolves in water.
Sponges, metal surfaces, dirt, water and wood pulp are all polar. Non-polar items include wax, Teflon, mineral base oil, duck back and water repellent.
It is important to note that additives are also victims. Once they are gone, they are gone. Think about the environment you work in, the products you produce and the types of pollutants
By your side every day. If you let contaminants attracted by additives enter your system, such as dirt, silica, and water, the additives will attach to the contaminants and settle to the bottom, or they will be filtered out and deplete your additive package.
There are some polar mechanisms worth discussing, such as particle encapsulation, water emulsification, and metal wetting.
Particle encapsulation means that the additive will adhere to the surface of the particle and encase it. These additives are metal deactivators, detergents and dispersants. They are used to peptize (disperse) soot particles to prevent agglomeration, settling and deposition, especially at low to moderate temperatures.
You will usually see this in the engine. Once any problems are detected through the proper oil analysis test board, it provides a good reason to fix and eliminate any problems.
When using oil additives, more is not always better. As more additives are mixed into the oil, sometimes no more benefits are gained, and sometimes the performance actually deteriorates. In other cases, the performance of the additives did not improve, but the service duration did increase.
In addition, increasing the percentage of certain additives may improve one characteristic of the oil while reducing another characteristic. When the specified concentration of additives becomes unbalanced, it will also affect the overall oil quality.
Some additives compete with each other for the same space on the metal surface. If a high concentration of antiwear agent is added to the oil, the effect of the corrosion inhibitor may be reduced. The result may be an increase in corrosion-related problems.
When the additive polar head attaches to the droplets of water, water emulsification occurs. These types of additives are emulsifiers. Please consider this the next time you look at the water in the reservoir.
Although it is important to remove the water, determine where the water enters the system, and repair it using root cause maintenance methods, you must also remember that the additive package has been affected. In terms of lubrication, this is called additive consumption. A suitable oil analysis report can determine the health status of residual additives in lubricating oil.
Metal wetting is when additives are fixed on the metal surface, which is what they should do. They are attached to the inside of gearboxes, gear teeth, bearings, shafts, etc.
The additives that perform this function are rust inhibitors, anti-wear (AW) and extreme pressure additives, oiliness agents and corrosion inhibitors.
AW additives are specifically used to protect metal surfaces under boundary conditions. They form a ductile gray film at moderate to high contact temperatures (150 to 230 degrees Fahrenheit).
Under boundary conditions, the AW film shears rather than the surface material.
A common antiwear additive is zinc dialkyldithiophosphate (ZDDP). It reduces the risk of metal-to-metal contact, which leads to increased heat, which leads to oxidation and negatively affects the strength of the film.
Additives play an important role in mechanical lubrication, whether it is to enhance or inhibit the base oil or to impart new characteristics to the base oil. Remember, when the additives disappear, they disappear, so don't forget to check your additive package.
There are many types of chemical additives mixed into the base oil to improve the performance of the base oil, suppress some of the undesirable properties of the base oil, and may give some new properties.
Additives usually account for 0.1% to 30% of the finished lubricant, depending on the lubricant's target application.
Lubricant additives are expensive chemicals, and creating appropriate additive mixtures or formulations is a very complex science. The difference between R&O oil and hydraulic oil, gear oil and engine oil is the choice of additives.
There are many lubricant additives available, and they are selected based on their ability to perform the desired function. They were chosen because they can be easily blended with the selected base oil, are compatible with other additives in the formulation, and are cost-effective.
Some additives play a role in the oil body (such as antioxidants), while other additives play a role on the metal surface (such as anti-wear additives and rust inhibitors).
These include the following general types of additives:
Oxidation is a general attack by oxygen in the air on the weakest components of the base oil. It always occurs at all temperatures, but will accelerate at higher temperatures and the presence of water, wear metals, and other contaminants.
It will eventually cause acid (corrosion) and sludge (causing surface deposits and viscosity increase) to form. Oxidation inhibitors, also known as oxidation inhibitors, are used to extend the life of the oil.
They are sacrificial additives that are consumed in fulfilling the duty of delaying the onset of oxidation, thereby protecting the base oil. They are found in almost all lubricating oils and greases.
These additives repel moisture on the metal surface by neutralizing the acid and forming a chemical protective barrier, thereby reducing or eliminating internal rust and corrosion.
Some of these inhibitors are specifically designed to protect certain metals. Therefore, an oil may contain multiple corrosion inhibitors. Likewise, they are common in almost all oils and greases. Metal passivators are another form of corrosion inhibitor.
Viscosity index improvers are very large polymer additives that partly prevent the oil from thinning (loss of viscosity) when the temperature rises. These additives are widely used to blend multi-grade engine oils, such as SAE 5W-30 or SAE 15W-40.
They are also responsible for providing better oil flow at low temperatures, thereby reducing wear and improving fuel economy. In addition, VI improvers are used to achieve high VI hydraulic oils and gear oils to improve start-up and lubrication at low temperatures.
In order to visualize the effect of the VI improver additive, imagine the VI improver as an octopus or coil spring, which remains coiled in a ball at low temperatures and has little effect on the viscosity of the oil.
Then, as the temperature rises, the additive (or octopus) expands or stretches its arms (making it larger) and prevents the oil from diluting too much at high temperatures.
The VI Improver does have some negative characteristics. Additives are large (high molecular weight) polymers, which makes them easily shredded or cut into small pieces by machine parts (shear forces). As we all know, it is difficult to use VI improvers for gears.
The permanent shear of the VI improver can cause significant viscosity loss, which can be detected by oil analysis. Due to the high shear forces in the load zone of the friction surface (for example, journal bearings), a second form of viscosity loss occurs.
It is thought that VI improvers lose their shape or uniform orientation and therefore lose some thickening ability.
The viscosity of the oil temporarily drops in the load zone, and then rebounds to normal viscosity after leaving the load zone. This feature actually helps reduce fuel consumption.
There are several different types of VI improvers (olefin copolymers are very common). Compared with low-cost, low-quality VI improvers, high-quality VI improvers are less susceptible to permanent shear loss.
These additives are often used to protect machine parts from wear and metal loss under boundary lubrication conditions. They are polar additives attached to the friction metal surface.
When metal-to-metal contact occurs under mixed lubrication and boundary lubrication conditions, they will chemically react with the metal surface.
They are activated by contact heat to form a film that minimizes wear. They also help protect base oils from oxidation and metals from corrosive acids.
These additives are "used up" by performing their functions, and then adhesive wear damage will increase. They are usually phosphorus compounds, the most common being zinc dialkyl dithiophosphate (ZDDP).
There are different versions of ZDDP-some for hydraulic applications, others for higher temperatures encountered in engine oil. ZDDP also has certain anti-oxidation and anti-corrosion properties. In addition, other types of phosphorus-based chemicals are used for anti-wear protection (such as TCP).
These additives are more chemically corrosive than AW additives. They chemically react with the metal (iron) surface to form a sacrificial surface film to prevent relatively rough welding and seizure caused by metal-to-metal contact (adhesive wear).
They are activated under high loads and resulting high contact temperatures. They are commonly used in gear oils and give these oils a unique, strong sulphur odor. These additives usually contain sulfur and phosphorus compounds (and occasionally boron compounds).
They may be corrosive to yellow metals, especially at higher temperatures, so they should not be used in worm gears and similar applications using copper-based metals. There are some chlorine-based extreme pressure additives, but they are rarely used due to corrosion problems.
Anti-wear additives and extreme pressure agents constitute a large class of chemical additives, which play a role in protecting the metal surface during the boundary lubrication process by forming a protective film or barrier on the worn surface.
As long as a hydrodynamic or elastohydrodynamic oil film is maintained between the metal surfaces, boundary lubrication will not occur, and these boundary lubrication additives are not required to perform their functions.
These boundary lubricant additives can protect the worn surface when the oil film breaks and rough contact is made under high load or high temperature.
The detergent has two functions. They help keep hot metal parts free of deposits (clean) and neutralize the acid formed in the oil. Detergents are mainly used in engine oils, and their properties are alkaline or alkaline.
They form the basis for the alkalinity of engine oil reserves and are called base number (BN). They are usually calcium and magnesium chemical materials. Barium-based cleaners have been used in the past, but now they are rarely used.
Because these metal compounds leave ash deposits when oil is burned, they may cause unwanted residues to be formed in high-temperature applications. Because of this ash problem, many original equipment manufacturers are specifying low ash oils for equipment operating at high temperatures. Detergent additives are usually used in combination with dispersant additives.
The dispersant is mainly found in engine oil with detergent, which helps to keep the engine clean and free of deposits. The main function of the dispersant is to keep the diesel soot particles finely dispersed or suspended in the oil (less than 1 micron).
The purpose is to keep the pollutants in suspension and not allow them to agglomerate in the oil, thereby minimizing damage and taking them out of the engine during oil changes. Dispersants are usually organic and ashless. Therefore, they are not easily detected by traditional oil analysis.
The detergent/dispersant additive combination can neutralize more acidic compounds and keep more pollutant particles in suspension. As these additives function to neutralize acids and suspended contaminants, they will eventually exceed their capacity, which will require oil changes.
The chemicals in this additive group have low interfacial tension, which weakens the walls of the oil bubbles and makes the foam bubbles more likely to burst. They have an indirect effect on oxidation by reducing the amount of air-oil contact.
Some of these additives are oil-insoluble silicone materials, which do not dissolve but are finely dispersed in the lubricating oil. Usually very low concentrations are required. If too much defoamer is added, it will have the opposite effect and promote further foaming and aeration.
Friction modifiers are commonly used in engine oil and automatic transmission oil to change the friction between the engine and transmission components. In engines, the focus is on reducing friction to improve fuel economy.
In the transmission, the focus is on improving the engagement of the clutch material. Friction modifiers can be considered as anti-wear additives for lower loads and are not activated by contact temperature.
The pour point of an oil is approximately the lowest temperature at which the oil maintains its fluidity. Wax crystals formed in paraffin mineral oil crystallize (become a solid) at low temperatures. The solid crystals form a lattice network that prevents the remaining liquid oil from flowing.
The additives in this group reduce the size of the wax crystals in the oil and the interaction between them, allowing the oil to continue to flow at low temperatures.
Demulsifier additives prevent the formation of a stable oil-water mixture or emulsion by changing the interfacial tension of the oil, thereby making it easier for water to coalesce and separate from the oil. This is an important characteristic of lubricants exposed to steam or water, so free water can settle and be easily drained in the reservoir.
Emulsifiers are used in oil-water-based metalworking fluids and refractory fluids to help form stable oil-water emulsions. Emulsifier additives can be thought of as glues that bind oil and water together because they usually separate from each other due to differences in interfacial tension and specific gravity.
Bactericides are usually added to water-based lubricants to control the growth of bacteria.
Tackifiers are viscous materials used in some oils and greases to prevent lubricants from being thrown off the metal surface during the rotational movement.
In order to be acceptable to both the mixer and the end user, the additives must be able to be processed in traditional mixing equipment, be stored stable, have no odor, and be non-toxic according to normal industry standards.
Since many are highly viscous materials, they are often sold to oil formulators as concentrated solutions in base oil carriers.
A few key points about additives: The more additives are not always better. An old saying, "A little bit is better, the more the better" is not necessarily correct when using oil additives.
As more additives are mixed into the oil, sometimes no more benefits are gained, and sometimes the performance actually deteriorates. In other cases, the performance of the additives did not improve, but the service duration did increase.
Increasing the percentage of certain additives may improve one characteristic of the oil while reducing another characteristic. When the specified concentration of additives becomes unbalanced, the overall oil quality will be affected.
Some additives compete with each other for the same space on the metal surface. If a high concentration of antiwear agent is added to the oil, the effect of the corrosion inhibitor may be reduced. The result may be an increase in corrosion-related problems.
It is very important to understand that most of these additives are consumed and depleted in the following ways:
Adsorption and separation mechanisms involve the mass transfer or physical movement of additives.
For many additives, the longer the oil is used, the less effective the remaining additive package will be in protecting the equipment.
When the additive package weakens, the viscosity increases, sludge begins to form, corrosive acids begin to attack the bearing and metal surfaces, and/or wear begins to increase. If you use low-quality oil, these problems will start to appear much faster.
It is for these reasons that the top lubricants that meet the correct industry specifications (such as API engine service classification) should always be selected. The following table can be used as a guide for a more comprehensive understanding of the types of additives and their functions in engine oil formulations.
Surface protection additive engine lubricant
Reduce friction and wear, prevent scratches and seizures
Zinc dithiophosphates, organic phosphates and acid phosphates; organic sulfur and chlorine compounds; sulfurized fats, sulfides, and disulfides
It chemically reacts with the metal surface to form a thin film with a lower shear strength than the metal, thereby preventing metal-to-metal contact
Prevent corrosion and rust of metal parts in contact with lubricant
Zinc dithiophosphate, metal phenates, alkaline metal sulfonates, fatty acids and amines
Preferentially adsorb the polar components on the metal surface to provide a protective film and/or neutralize corrosive acids
Keep the surface free of deposits and neutralize corrosive acids
Metal organic compounds of barium, calcium and magnesium phenates, phosphates and sulfonates
Chemically react with sludge and varnish precursors to neutralize them and keep them soluble
Keep insoluble soot dispersed in the lubricant
Organic complexes of polymeric alkyl thiophosphonates and alkyl succinimides, nitrogen-containing compounds
Pollutants are combined with dispersant molecules through polar attraction, preventing aggregation and staying in suspension due to the dispersant's solubility
Organic fatty acids and amines, lard, high molecular weight organic phosphorus and phosphate esters
Preferential adsorption of surface active substances
Make the lubricant flow at low temperatures
Alkylated naphthalene and phenolic polymers, polymethacrylate
Modify wax crystal formation to reduce interlocking
Organic phosphates, aromatic hydrocarbons, halogenated hydrocarbons
A chemical reaction with the elastomer causes slight swelling
Reduce the speed of viscosity change with temperature
Polymers and copolymers of methacrylate, butadiene olefin and alkylated styrene
The polymer expands as the temperature rises to counteract the thinning of the oil
Lubricant Protection Additives Engine Lubricants
Prevent lubricants from forming persistent foam
Silicone polymers and organic copolymers
Reduce surface tension to accelerate foam collapse
Zinc dithiophosphate, hindered phenol, aromatic amine, sulfurized phenol
Decompose peroxides and stop free radical reactions
Reduce the catalytic effect of metals on the oxidation rate
Organic complexes containing nitrogen or sulfur, amines, sulfides and phosphites
Form an inert film on the metal surface by complexing with metal ions
It is obvious from the above information that most oils used for lubricating equipment contain a lot of chemical components. They are a complex mixture of chemicals, balanced with each other, and need to be respected.
It is for these reasons that mixing different oils and adding additional lubricant additives should be avoided.
There are hundreds of chemical additives and supplementary lubricant regulators available. In some professional applications or industries, these additives may have a place in improving lubrication.
However, some supplementary lubricant manufacturers make exaggerated and/or unsubstantiated claims about their products, or they fail to mention the possible negative effects of additives.
Be extra careful when selecting and applying these products, or it is best to avoid using them. If you want a better oil, you must first buy a better oil and leave the chemistry to someone who knows what you are doing.
The use of aftermarket additives usually invalidates the oil and equipment warranty because the final formulation has never been tested and approved. Buyers beware.
When considering the use of aftermarket additives to solve problems, it is wise to remember the following rules:
Rule #1 You can't turn inferior lubricants into high-quality products just by adding additives. It is illogical to buy inferior oil products and try to use some special additives to overcome its inferior lubricating properties.
Rule #2 Some laboratory tests may be tricked to provide positive results. Some additives can fool a given test to provide a passing result. Usually multiple oxidation and abrasion tests are performed to obtain better additive performance indicators. Then carry out the actual field test.
Rule #3 Base oil can only dissolve (carry) a certain amount of additives. Therefore, adding supplemental additives to oils that have low solubility or that have been saturated with additives may only mean that the additives will precipitate out of solution and remain at the bottom of the crankcase or oil pan. The additive may never perform its claimed or intended function.
If you choose to use aftermarket additives, please take the following precautions before adding any supplementary additives or oil conditioners to the lubrication system:
Determine if there are actual lubrication problems. For example, oil contamination problems are usually related to poor maintenance or insufficient filtration, not necessarily to poor lubrication or poor oil quality.
Choose the right supplementary additives or oil conditioners. This means spending time studying the composition and compatibility of various products on the market.
Insist on providing real field test data to verify the claims about the effectiveness of the product.
Please consult a reputable independent oil analysis laboratory. Before adding supplemental additives, perform at least two analyses of existing oils. This will establish a reference point.
After adding special additives or regulators, continue to analyze the oil regularly. Only through this method of comparison can objective data on the effectiveness of additives be obtained.
There is a lot of controversy surrounding the application of supplementary additives. However, certain supplementary lubricant additives do reduce or eliminate friction in certain applications, such as machine tool methods, extreme pressure gear drives, and certain high-pressure hydraulic system applications.