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Industrial lubricants are increasingly providing a rich environment for microbial growth and proliferation. Most of the knowledge of lubricant biodeterioration has been extrapolated from field and laboratory experience with metalworking fluids. Compositionally more complex than most lubricants, metalworking fluids are either solutions or emulsions of 5 to 10% coolant concentrate in water. The fatty acids, sulfurized oils, glycols and other organic components of metalworking fluids and other lubricants provide a rich food source for microbes. Coolant recirculation provides aeration to support aerobic microbial activity. Most lubrication sysstems do not share this characteristic with metalworking fluid systems. Lubricant flow tends to be slower and absorbs less entrained air. Recirculating systems provide an ideal environment for biofilms to grow. Large systems may have several square miles of surface area for oxygen to be exposed to lubricant. Except for fire retardant hydraulic fluids, with their high water content, moisture enters the system through condensation.

Microbes are most prevalent on system surfaces where condensation co-mingles with lubricant to support development. The microbes inhabiting the biofilms that form on these surfaces act like fixed-film biological reactors; drawing nutrients from the coolant and excreting waste products back into the stream. The net effect is lubricant biodeterioration.

The objective of contamination control is primarily to prevent biodeterioration. A secondary, but often consequential objective is to minimize biomass accumulation. Properly used as part of an overall lubricant management strategy, biocides play a major role in inhibiting both biodeterioration and biomass accumulation.


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Dr. Frederick Passman, PhD is a Certified Metalworking Fluids Specialist with over 35 years experience in Environmental & Industrial Microbiology. His company, Biodeterioration Control Associates, Inc. (BCA) provides clients with unparalleled expertise in Microbial Contamination Control.

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