Page 5 - Coolant - Houghton Training

The Biology of Metalworking Fluids

Metalworking fluids - coolant - contained carcinogenic materials until the 1970s, when

they were outlawed, as was the practice of disposing metalworking fluid down the

drain. Shortly afterward, machine shop workers noticed that their sumps would start
to smell after a few weeks, or even days. Some machine shops even reported that

when their machines would start up, not only would the shop reek of rotten eggs (the

infamous Monday morning smells) but that they could see a cloud of green haze linger
about the machine. In addition, workers would develop rashes, eye or lung irritation,

and other health problems. In many cases the very paint would fall off machines, and

seals and gaskets would disintegrate. These sorts of problems hadn’t happened in the
old days, so it was quite a while before anyone could really trace the source of what

was going on.

The problem was bacteria. The very bugs that make our bread and wine are also good
at turning the oils in coolant sumps into their own version of Club Med. The challenge

for chemists was to develop metalworking fluids that were resistant to bacterial

attack, yet not harmful to humans. The problem with that is what is usually bad for

bacteria is also bad for people. This ‘cold war’ of chemist against bacteria continues
even today.