Page 3 - Coolant - Houghton Training

Metal Working Fluids - Chemistry

The aging of coolant revolves primarily upon chemical activity. Over time, acids are

introduced into the coolant system via bacterial activity (refer to the Biology section of

the Basics for further information on bacteria). The bacteria comes mainly from the
water that is used. This is why it is important, when topping off your sump, to add a

reduced coolant mix rather than straight water.

The acids that accumulate in your sump are hydrochloric acid (HCl) and hydrogen

sulfide (H2S). These acids will eventually bring down the sump’s pH, causing rust and
corrosion, bad odors, and possible skin reactions.

For those who have swimming pools, the concept called pH buffering is understood.

Buffering means that there is some compound, usually a carbonate of some form (like
baking soda) that remains in solution but does not fully dissolve. Coolant formulators

add these buffering components to their formula, but as more acids accumulate, they

will combine with these reserved carbonates and neutralize. Once all the reserves are
used, additional accumulation of more acid will impact the pH of the sump