4. Physiologically active additives

4.1 Biocides

Aqueous metalworking fluids and, possibly, fire-resistant aqueous hydraulic fluids (HFA, HFB, HFC fluids), in contact with the outside environment, are susceptible to contamination by microorganisms of various origins (bacteria, fungi and algae) which do not develop at the same time, but can cause serious inconvenience in machining and forming shops.

• These microorganisms, which develop in the continuous phase of water, are of several types.

• Areobic bacteria

  They thrive in aerated fluids, as they need oxygen, i.e. during periods of machine operation. They prefer neutral to alkaline pH and warm temperatures (30 to 40°C). The most troublesome...