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Biocides for Metal-Stamping and Machining Fluids - Questions and Answers

Joseph L. Purnhagen ,

Joseph L. Purnhagen is Global Commercial Manager of Metal Processing Additives at The Lubrizol Corporation

Aqueous metal-stamping and machining fluid environments contain all the components to support microbial growth. When is microbial growth a problem? What should metal stampers know to make informed decisions on the use of biocides to control or eliminate that growth?

Unchecked Microbes Cause Problems
Uncontrolled microbial growth in metalworking fluid emulsions can create numerous negative consequences for fluid users, including:
  • Degradation of fluid performance, affecting emulsion stability, corrosion protection, lubrication, etc.;
  • Reduction of useful fluid life, causing unnecessary expense related to production downtime and fluid-replacement costs;
  • Foul odors resulting in an unpleasant working environment;
  • Potential worker exposure to hazardous microbial growth that has been associated with dermal and respiratory irritation and/or disease.

Aqueous metal-stamping and machining-fluid environments contain all the necessary components to support microbial growth: water, organic materials, unintended contaminants and elevated temperatures.

Metalworking fluid biocides are specifically designed to control and/or eliminate microbial growth in aqueous metalworking fluid systems such as those employed in metal-stamping and machining operations. Proper application of registered biocidal products helps ensure that fluids offer a long and productive useful life in a safe working environment for manufacturing employees.

These questions and answers can help metal stamping professionals make informed choices regarding the use of biocides in their fluid applications.

What are the differences between concentrate and tankside applications?
Metalworking fluid concentrates are typically supplied to manufacturing locations for dilution into water at the site.

Concentrate treatment application refers to incorporation of a biocide in the supplied fluid concentrate. Treatment levels of biocide in the metalworking fluid concentrate should be selected to deliver an appropriate amount of active chemistry in the final in-use dilution. Your lubricant supplier should be able to provide proper dilution instructions.

Tankside treatment application refers to the use of a biocide directly into the diluted, in-use metalworking fluid at the manufacturing location. This approach supplements microbial control and/or corrects problem levels of microbial contamination. Tankside treatment levels of biocide in the in-use dilution should be selected to deliver an appropriate amount of active chemistry with consideration of the total system volume being treated.

Is one biocide enough?Is one biocide enough?
Active substances used in metalworking fluid biocides are typically effective at controlling either bacteria (bactericides) or fungi (fungicides). To provide broad-spectrum control against both bacteria and fungi, a combination of active substances is required. Combination additive packages are available to provide broad-spectrum control in general applications. Additionally, the long-term viability of a fluid system will benefit from the use of multiple active substances to reduce acclimation of microbes to one particular biocidal compound.

Can metalworking fluid biocides guarantee control of microbial growth? Can metalworking fluid biocides guarantee control of microbial growth?
Though key, proper use of biocides is only one part of a total metalworking fluid maintenance program that will ensure maximum performance, fluid life and worker safety. Other factors include fluid-concentration control, avoidance of unnecessary contaminants, removal of unavoidable contaminants and proper fluid aeration. Best practices prior to fluid changeout can include the use of biocidal system cleaners to ensure a clean environment for the fresh fluid charge. Appropriate metalworking fluid biocide usage in combination with careful attention to fluid maintenance offers the best overall solution in metal-stamping and metalworking environments.

Are metalworking fluid biocides safe to use and handle?
Safe handling practices for metalworking fluid biocides, like all chemicals for industrial applications, should not be overlooked. Metalworking biocide products offered by reputable suppliers have been thoroughly tested to ensure an appropriate balance of efficacy and safety at the recommended use conditions. But be sure to use biocides safely. Always read the label and product information before use.

Can microbial growth be controlled without metalworking fluid biocides?

Attempting to control microbial growth with chemicals that have not been specifically designed or approved for metalworking fluid biocide application can be dangerous. Unknown hazards or fluid performance incompatibilities may be associated with the use of such chemicals. All products approved for use as metalworking fluid biocides by established regulatory agencies have been subjected to intensive scrutiny and evaluation regarding their efficacy and risk factors relative to likely exposure scenarios in metalworking fluid environments.

If some biocide is good, is more even better?
Treat rates of metalworking fluid biocides should not exceed the recommended maximum concentrations based on ranges provided by reputable biocide suppliers. Exceeding recommended dosage levels can result in concentration levels above what has been demonstrated to be safe in stamping or machining environments. Treat rates below the recommended ranges should also be avoided to prevent microbial acclimation to the biocide chemistry that will result in resistance to future treatments.

Formaldehyde Condensates as Biocides—Lubrizol’s Position
A re-classification of formaldehyde by the International Agency for Research on Cancer has prompted much of the heightened discussion in recent history. Exposure to extremely high levels of airborne formaldehyde has shown carcinogenic tendencies. However, the levels of formaldehyde exposure that could potentially be experienced in metalworking fluid environments such as metal-stamping operations do not approach even the most stringent permissible exposure limits set with human safety in mind.

Formaldehyde condensates have served as the primary biocidal products for use in metalworking fluids for many decades. In fact, all of the active substances currently being registered by Lubrizol in the European Biocidal Products Directive can be classified as formaldehyde condensates. Lubrizol is fully committed to supporting this class of products to allow for their continued successful use in metalworking fluids for years to come. It is Lubrizol’s position that formaldehyde condensates offer metalworking fluids the most effective means of microbial control when considering application efficacy, economic, health, safety and environmental issues in total, as compared with alternative approaches.


Discussion Question: What factors have led your stamping operation to consider employing metalworking fluid biocides?

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