The challenges in formulating water-based metalworking fluids (MWFs) continue to increase as end-users demand better performance over longer periods of time under severe conditions. With concerns about foam, hard water stability and microbial contamination, MWFs need to be complex formulations so they can fulfill their basic functions of lubricity, cooling, corrosion protection and flushing metal chips.
Of particular concern are fluids produced for metal removal applications. The list of additives that can be incorporated into an MWF is shown in Table 1. Finding the right combination of additives for specific machining applications while accounting for the operating conditions makes it imperative that the decision-making formulator have the proper information.
TYPES OF ADDITIVES USED IN MWFs |
Antimicrobial pesticides (biocides) |
Antimist agents (usually tankside addition) |
Antioxidants (mainly straight oils) |
Corrosion inhibitors |
Coupling agents |
Defoamers |
Dyes |
Emulsifiers |
Extreme pressure agents |
Lubricity additives |
Metal deactivators |
Reserve alkalinity boosters (amines) |
Wetting agents |
Table 1. MWFs are formulated with a wide range of additives. (Table courtesy of Chemical Solutions.)
This article offers insight on how metal removal fluids should be formulated in the 21st Century. We interviewed multiple industry experts with a variety of perspectives.
Key parameters
To begin with, an assessment is made about the key parameters that MWF formulators must consider when preparing a product. Society of Tribologists and Lubrication Engineers (STLE) member Gabe Kirsch, strategic product manager metalworking additives, North America for The Lubrizol Corp. in Wickliffe, Ohio, says, “The key parameters to consider are the overall cost of use, foam control, biostability, lubricity, corrosion and stain protection, temperature stability as the concentrate and as a dilution, odor, color and hard water stability when diluted and the final product GHS statements.”
Dr. Anthony Jarvis, R&D manager for Global MWF Product Development at Afton Chemical Ltd. in Manchester, UK, focuses on the specific technical, economic and regulatory considerations that are required when formulating MWFs. “The key technical parameters that must be considered by formulators are foaming, resistance to microbial attack, hard water stability/emulsion stability, corrosion inhibition/staining and tool life,” he says. “The balance between the cost of the MWF and its life expectancy in the field is the paramount economic factor.
“With regard to regulatory issues,” Jarvis adds, “the use of substances that have regulatory concerns or are restricted under the chemical legislation of a specific region must be considered. MWF formulators will need to take into account reactive chemistry and minimize the GHS (the Global Harmonized System of Classification and Labeling Chemicals) classification and subsequent labeling of their products.”
STLE-member Dr. James MacNeil, product manager for Qualice LLC in Hamlet, N.C., feels that the regulatory factors will be the most significant issue and even more significant now and in the future than it was in the past. He raises three important questions that all formulators must consider in working with any additive.
- Are the components registered in all of the countries where they may be used?
- Are there any ongoing regulatory investigations clouding the future availability of the components?
- Are there any possible exposure concerns?
MacNeil says, “One additional issue that must be examined is the potential interactions among components that could potentially generate a new material such as a salt that is not registered on one of the commercial country databases (such as the U.S. TSCA Inventory).”
STLE-member Nicole Webb, technical sales representative, MWFs for ANGUS Chemical Co. in Buffalo Grove, Ill., says, “Two of the most critical parameters to consider when formulating high-performance MWFs are cost and the life-cycle environmental, health and safety characteristics of the formulation. In today’s market, regulatory registration in multiple geographies is often mandatory, and unsatisfactory labeling or the presence of certain impurities such as formaldehyde, phenol, secondary amines and boron can be deal breakers.”
Webb stresses that multifunctionality is becoming crucial due to the ever-growing list of complex needs formulators must assess in preparing MWFs. She says, “Formulators are no longer looking for one product to meet each performance criteria but, rather, products that meet multiple performance objectives, including labeling requirements.”
STLE-member Dr. Michael Stapels, technical manager for Kao Chemicals GmbH in Emmerich, Germany, stresses that fluid longevity is his most important key parameter, particularly with regard to robustness in the presence of bacteria, fungus and hard water. He says, “Foam control, along with workers’ health and environmental issues, will also play more important roles in the future. The latter issue is consistent with the more active role of regulatory authorities in influencing the additives that can be used in MWFs.”
What are other considerations and options?
Learn more about water-based MWFs at STLE.org
This article is excerpted and reprinted with permission from the March 2017 issue of Tribology and Lubrication Technology (TLT), the official monthly magazine of the Society of Tribologists and Lubrication Engineers, an international not-for-profit technical society headquartered in Park Ridge, Illinois. Read the full article at stle.org.
References
- Passman, F., Canter. N., Rotherham, R., Byers, J. and Eachus, A. (2016), “MWF Biocides Part II,” TLT, 72 (3), pp. 46-57.
About STLE
The Society of Tribologists & Lubrication Engineers (STLE) is the premier technical society serving the needs of over 12,000 individuals and 250 companies and organizations that comprise the tribology and lubrication engineering business sector. STLE members are employed by the world’s leading corporations, academic institutions and by governmental agencies dealing with science and technology. STLE supports these distinguished technical experts with a variety of professional education and certification programs.
About the Author
Neil Canter heads his own consulting company, Chemical Solutions, in Willow Grove, Pa. Ideas for Tech Beat items can be sent to him at neilcanter@comcast.net.
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Is it possible to formulate a water based fluid only with a lubricity improver? It can be used for non ferrous applications.
May you kindly also explain what types of surfactant are more suitable for metal working fluids?