Page 6 - Coolant - Houghton Training

The Biology of Metalworking Fluids

Since the early days of this cold war we have learned much more about the ecology of

coolant sumps. There are many species of bacteria that can live there, most of which
like oxygen environments, but some of which that don’t. There are also many varieties

of fungi that live there too. And once enough bacteria have congregated in one place,

they have a way of signaling each other (called quorum sensing) so that they form a
colony. One of the things these colonies do to protect themselves is start producing a

protein carbohydrate complex that science calls a biofilm, and the rest of us call slime,

or mucus. Once a biofilm has formed, the only way known to get rid of it is to scrape it
off.

Biofilm are far more prevalent than we used to think. Scum on your tub, tartar on your
teeth, and your congested sinuses are all forms of biofilms. Cystic fibrosis and serious

pneumonia are forms of biofilms that kill (where most current research is focused). In

the case of the lowly machine sump, you see the biofilm as the skin on the surface of
the sump, what many of us used to call tramp oils.