- Common lubricant properties: clean, cool, lubricate and seal.
- Lubricant additives are chemical components or blends that provide one or more functions in the fluid, when used at a specific treat rate.
- Including a Certified Lubrication Specialist™ (CLS) chemist on your team can help safely manage additives.
Common lubricant properties
In most scenarios, lubricants:
- Clean: wash away metal wear debris or chips in metalworking applications
- Cool: remove heat from machine or machining surfaces
- Lubricate: keep moving surfaces separate
- Seal: fill in surface voids and gaps
Once you identify the right oil for the project, lubricant additives can help achieve the desired results.
In particular, metalworking fluid (MWF) additives can also prevent undesirable events such as:
- poor surface finish
- chemical attack on the work piece
- mechanical damage
- metallurgical change to the mechanism
- thermal damage
- electrical changes
However, working with MWFs can have its hazards, which can lead to employee health and safety issues, plug filters and cause operational problems. One must watch for and minimize these effects, including:
- mist, which may lead to respiratory problems
- skin conditions such as dermatitis
- microbial and fungal growth
Lubricant additives, explained
Additives are a chemical component or blend used at a specific treat rate, generally from < 1 to 35 percent, to provide one or more functions in the fluid. Ideally, additive components are multifunctional. They are soluble in mineral oil, water or sometimes both.
Second, additives offer or help with a wide variety of functions, such as:
- boundary lubricity
- extreme pressure (EP)
- inhibiting corrosion
- boosting reserve alkalinity
- antimicrobial pesticide
- antifoam additives and defoamers
With such a variety of effects, chemists often look for additives that can be multifunctional as well as compatible with different chemicals in a formulation, both with other additives as well as the base fluid.
Looking for additives for your lubrication formulation?
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Performance-related lubricant additives
The properties of the oil are augmented by lubricant additives.
- Boundary Lubricity Additives enhance fluid lubricity by adsorbing on the metal surface to form a film, limiting metal-tometal contact. Examples include lard and canola oil. Solid lubricants can also be used for boundary lubrication.
- Extreme Pressure Additives are a special type of boundary lubricity additive that form a metal salt layer between mating surfaces that limit friction, wear and damage. Examples include:
- Zinc dialkyl dithiophosphate (ZDDP)
- Chlorinated paraffins
- Sulfurized lard oils
- Phosphate esters
- Overbased calcium sulfonates
- Corrosion Inhibitors prevent the fluid from corroding machine surfaces, metal work piece, cutting tool and machine tool. Examples include:
- Overbased sulfonates
- Reserve Alkalinity Additives essentially serve as a buffer, neutralizing acidic contaminants to preserve the fluid’s corrosion protection and maintain the pH in a suitable range. Examples include alkanolamines like:
- Monoethanolamine (MEA)
- Triethanolamine (TEA)
- Aminomethylpropanol (AMP)
- 2-(2-aminoethoxy) ethanol
- Metal Deactivators prevent the MWF from staining nonferrous alloys (such as copper and brass) and reduce corrosion when dissimilar metals contact each other. They act by forming a protective coating on the metal surface. Examples include:
- Detergents stabilize dirt and wear debris in oil formulations.
- Emulsifiers reducing interfacial tension between incompatible components by forming micelles, thereby stabilizing oil-soluble additives in water-dilutable MWFs. These micelles —droplets in a colloidal system—then can remain suspended in the fluid. Milk is an emulsion. In MWFs, examples include sodium petroleum sulfonate and alkanolamine salts of fatty acids.
- Couplers help stabilize water-dilutable MWFs in the concentrate to prevent component separation. Couplers facilitate formation of soluble oil emulsions. Examples include:
- Propylene glycol
- Glycol ethers
- Nonionic alkoxylates
- Chelating Agents (also known as water softeners or conditioners) reduce the destabilizing effect of hard water (calcium and magnesium ions) on MWF emulsions. An example might be ethylenediaminetetracetic acid (EDTA).
- Antimist Additives minimize the amount of lubricant that disperses into the air during machining. They are typically polymers and/or wetting agents. For oil-based systems, ethylene, propylene copolymers and polyisobutenes are used. For water-based systems, polyethylene oxides are common.
- Dyes change the color of the lubricant or MWF, usually as requested by the customer. In water-diluted fluids, their main value is to indicate that product is present, since some of these can be clear and water-like in appearance. However, dyes carry some negatives:
- They can stain skin and paint
- Some water-soluble dyes are unstable and can change color
- Some dyes can pass through waste treatment systems, resulting in pollution downstream.
Additives must perform even more tasks when the lubricant is a MWF.
Use of some additives can carry substantial risk, so working with a specialized chemist—such as one with STLE certification—is critical. It is also important to have a good working relationship with lubricant, MWF and additive suppliers. This team can keep your system in balance and safely working at optimum performance levels.
Learn more about lubricant additives
For a more in-depth overview of lubricant additives and their applications, see Tribology & Lubrication Technology’s article: The Mysterious World of Lubricant Additives.
The views, opinions and technical analyses presented here are those of the author, and are not necessarily those of UL, ULProspector.com or Knowledge.ULProspector.com. While the editors of this site make every effort to verify the accuracy of its content, we assume no responsibility for errors made by the author, editorial staff or any other contributor. All content is subject to copyright and may not be reproduced without prior authorization from Prospector.