Page 7 - Coolant - Houghton Training
P. 7
The Biology of Metalworking Fluids
Bacteria exude waste products while they live (including acids), and decay when they
die. Their life cycle can last from 20 minutes for nicely warmed oxygen loving aerobes,
to as long several hours for oxygen hating anaerobes. Some bacteria can do both,
which makes the job of identifying them harder. Decay products include HCl and H2S,
and these are the acids that help degrade the coolant.
This is one cold war that we can’t win. Bacteria are always present everywhere: In the
skin we shed, in the air we breathe, and in the water we mix with the coolant. As soon
as a layer of oil collects in the sump, an oxygen dead layer forms (because aerobic
bacteria consume the oxygen as part of their metabolic cycle) and the anaerobic
bacteria start to thrive. In fact, they like to consume the oil itself as a food source.
